ImageField.cs source code in C# .NET

Source code for the .NET framework in C#

                        

Code:

/ Dotnetfx_Vista_SP2 / Dotnetfx_Vista_SP2 / 8.0.50727.4016 / DEVDIV / depot / DevDiv / releases / whidbey / NetFxQFE / ndp / fx / src / xsp / System / Web / UI / WebControls / ImageField.cs / 1 / ImageField.cs

                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Web.UI.WebControls { 
 
    using System;
    using System.Collections; 
    using System.Collections.Specialized;
    using System.ComponentModel;
    using System.Drawing.Design;
    using System.Globalization; 
    using System.IO;
    using System.Security.Permissions; 
    using System.Web.Util; 

    ///  
    /// Creates a field bounded to a data field in a .
    /// 
    [AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.Minimal)]
    [AspNetHostingPermission(SecurityAction.InheritanceDemand, Level=AspNetHostingPermissionLevel.Minimal)] 
    public class ImageField : DataControlField {
 
        ///  
        ///    Specifies a string that represents "this". This field is read-only. 
        ///  
        public static readonly string ThisExpression = "!";

        private PropertyDescriptor _imageFieldDesc;
        private PropertyDescriptor _altTextFieldDesc; 
        string _dataField;
 
        ///  
        /// Initializes a new instance of a  class.
        ///  
        public ImageField() {
        }

        [ 
        Localizable(true),
        WebCategory("Appearance"), 
        DefaultValue(""), 
        WebSysDescription(SR.ImageField_AlternateText)
        ] 
        public virtual string AlternateText {
            get {
                object o = ViewState["AlternateText"];
                if (o != null) { 
                    return (string)o;
                } 
                return String.Empty; 
            }
            set { 
                if (!String.Equals(value, ViewState["AlternateText"])) {
                    ViewState["AlternateText"] = value;
                    OnFieldChanged();
                } 
            }
        } 
 
        /// 
        ///    Gets or sets the property that determines whether the field treats empty string as 
        ///    null when the field values are extracted.
        /// 
        [
            WebCategory("Behavior"), 
            DefaultValue(true),
            WebSysDescription(SR.ImageField_ConvertEmptyStringToNull) 
        ] 
        public virtual bool ConvertEmptyStringToNull {
            get { 
                object o = ViewState["ConvertEmptyStringToNull"];
                if (o != null) {
                    return (bool)o;
                } 
                return true;
            } 
            set { 
                ViewState["ConvertEmptyStringToNull"] = value;
            } 
        }

        [
        WebCategory("Data"), 
        DefaultValue(""),
        TypeConverter("System.Web.UI.Design.DataSourceViewSchemaConverter, " + AssemblyRef.SystemDesign), 
        WebSysDescription(SR.ImageField_DataAlternateTextField) 
        ]
        public virtual string DataAlternateTextField { 
            get {
                object o = ViewState["DataAlternateTextField"];
                if (o != null) {
                    return (string)o; 
                }
                return String.Empty; 
            } 
            set {
                if (!String.Equals(value, ViewState["DataAlternateTextField"])) { 
                    ViewState["DataAlternateTextField"] = value;
                    OnFieldChanged();
                }
            } 
        }
 
        ///  
        ///    Gets or sets the display format of alternate text in this
        ///       field. 
        /// 
        [
        WebCategory("Data"),
        DefaultValue(""), 
        WebSysDescription(SR.ImageField_DataAlternateTextFormatString)
        ] 
        public virtual string DataAlternateTextFormatString { 
            get {
                object o = ViewState["DataAlternateTextFormatString"]; 
                if (o != null)
                    return (string)o;
                return String.Empty;
            } 
            set {
                if (!String.Equals(value, ViewState["DataAlternateTextFormatString"])) { 
                    ViewState["DataAlternateTextFormatString"] = value; 
                    OnFieldChanged();
                } 
            }
        }

        ///  
        ///     Gets or sets the field name from the data model bound to this field.
        ///  
        [ 
        WebCategory("Data"),
        DefaultValue(""), 
        TypeConverter("System.Web.UI.Design.DataSourceViewSchemaConverter, " + AssemblyRef.SystemDesign),
        WebSysDescription(SR.ImageField_ImageUrlField)
        ]
        public virtual string DataImageUrlField { 
            get {
                if (_dataField == null) { 
                    object o = ViewState["DataImageUrlField"]; 
                    if (o != null)
                        _dataField = (string)o; 
                    else
                        _dataField = String.Empty;
                    }
                return _dataField; 
            }
            set { 
                if (!String.Equals(value, ViewState["DataImageUrlField"])) { 
                    ViewState["DataImageUrlField"] = value;
                    _dataField = value; 
                    OnFieldChanged();
                }
            }
        } 

        [ 
        WebCategory("Data"), 
        DefaultValue(""),
        WebSysDescription(SR.ImageField_ImageUrlFormatString) 
        ]
        public virtual string DataImageUrlFormatString {
            get {
                object o = ViewState["DataImageUrlFormatString"]; 
                if (o != null) {
                    return (string)o; 
                } 
                return String.Empty;
            } 
            set {
                if (!String.Equals(value, ViewState["DataImageUrlFormatString"])) {
                    ViewState["DataImageUrlFormatString"] = value;
                    OnFieldChanged(); 
                }
            } 
        } 

        ///  
        ///    Gets or sets the property that determines what text is displayed if the value
        ///    of the field is null.
        /// 
        [ 
        Localizable(true),
        WebCategory("Behavior"), 
        DefaultValue(""), 
        WebSysDescription(SR.BoundField_NullDisplayText)
        ] 
        public virtual string NullDisplayText {
            get {
                object o = ViewState["NullDisplayText"];
                if (o != null) { 
                    return (string)o;
                } 
                return String.Empty; 
            }
            set { 
                if (!String.Equals(value, ViewState["NullDisplayText"])) {
                    ViewState["NullDisplayText"] = value;
                    OnFieldChanged();
                } 
            }
        } 
 
        [
        WebCategory("Behavior"), 
        DefaultValue(""),
        Editor("System.Web.UI.Design.ImageUrlEditor, " + AssemblyRef.SystemDesign, typeof(UITypeEditor)),
        UrlProperty(),
        WebSysDescription(SR.ImageField_NullImageUrl) 
        ]
        public virtual string NullImageUrl { 
            get { 
                object o = ViewState["NullImageUrl"];
                if (o != null) { 
                    return (string)o;
                }
                return String.Empty;
            } 
            set {
                if (!String.Equals(value, ViewState["NullImageUrl"])) { 
                    ViewState["NullImageUrl"] = value; 
                    OnFieldChanged();
                } 
            }
        }

        ///  
        ///    Gets or sets the property that prevents modification to data
        ///       in this field. 
        ///  
        [
        WebCategory("Behavior"), 
        DefaultValue(false),
        WebSysDescription(SR.ImageField_ReadOnly)
        ]
        public virtual bool ReadOnly { 
            get {
                object o = ViewState["ReadOnly"]; 
                if (o != null) 
                    return (bool)o;
                return false; 
            }
            set {
                object oldValue = ViewState["ReadOnly"];
                if (oldValue == null || (bool)oldValue != value) { 
                    ViewState["ReadOnly"] = value;
                    OnFieldChanged(); 
                } 
            }
        } 

        protected override void CopyProperties(DataControlField newField) {
            ((ImageField)newField).AlternateText = AlternateText;
            ((ImageField)newField).ConvertEmptyStringToNull = ConvertEmptyStringToNull; 
            ((ImageField)newField).DataAlternateTextField = DataAlternateTextField;
            ((ImageField)newField).DataAlternateTextFormatString = DataAlternateTextFormatString; 
            ((ImageField)newField).DataImageUrlField = DataImageUrlField; 
            ((ImageField)newField).DataImageUrlFormatString = DataImageUrlFormatString;
            ((ImageField)newField).NullDisplayText = NullDisplayText; 
            ((ImageField)newField).NullImageUrl = NullImageUrl;
            ((ImageField)newField).ReadOnly = ReadOnly;
            base.CopyProperties(newField);
        } 

        protected override DataControlField CreateField() { 
            return new ImageField(); 
        }
 
        /// 
        /// Extracts the value(s) from the given cell and puts the value(s) into a dictionary.  Indicate includeReadOnly
        /// to have readonly fields' values inserted into the dictionary.
        ///  
        public override void ExtractValuesFromCell(IOrderedDictionary dictionary, DataControlFieldCell cell, DataControlRowState rowState, bool includeReadOnly) {
            Control childControl = null; 
            string dataField = DataImageUrlField; 
            object value = null;
            bool includeNullValue = false; 

            if (((rowState & DataControlRowState.Insert) != 0) && !InsertVisible) {
                return;
            } 

            if (cell.Controls.Count == 0) { // this should happen only in design mode 
                Debug.Assert(DesignMode, "Unless you're in designmode, there should be a control in the cell."); 
                return;
            } 

            childControl = cell.Controls[0];

            Image image = childControl as Image; 
            if (image != null) {
                if (includeReadOnly) { 
                    includeNullValue = true; 
                    if (image.Visible) {
                        value = image.ImageUrl; 
                    }
                }
            }
            else { 
                TextBox editBox = childControl as TextBox;
                if (editBox != null) { 
                    value = editBox.Text; 
                    includeNullValue = true;    // just in case someone wrote a derived textbox that returns null for Text.
                } 
            }

            if (value != null || includeNullValue) {
                if (ConvertEmptyStringToNull && value is string && ((string)value).Length == 0) { 
                    value = null;
                } 
 
                if (dictionary.Contains(dataField)) {
                    dictionary[dataField] = value; 
                }
                else {
                    dictionary.Add(dataField, value);
                } 
            }
        } 
 
        /// 
        /// Returns the formatted value of the image url 
        /// 
        protected virtual string FormatImageUrlValue(object dataValue) {
            string formattedValue = String.Empty;
            string formatting = DataImageUrlFormatString; 

            if (!DataBinder.IsNull(dataValue)) { 
                string dataValueString = dataValue.ToString(); 

                if (dataValueString.Length > 0) { 
                    if (formatting.Length == 0) {
                        formattedValue = dataValueString;
                    }
                    else { 
                        formattedValue = String.Format(CultureInfo.CurrentCulture, formatting, dataValue);
                    } 
                } 
            }
            else { 
                return null;
            }
            return formattedValue;
        } 

        ///  
        /// Returns the alternate text to be used for accessibility 
        /// 
        protected virtual string GetFormattedAlternateText(Control controlContainer) { 
            string altTextField = DataAlternateTextField;
            string altTextFormatString = DataAlternateTextFormatString;
            string formattedAlternateText;
 

            if (altTextField.Length > 0) { 
                object value = GetValue(controlContainer, altTextField, ref _altTextFieldDesc); 
                string strValue = String.Empty;
                if (!DataBinder.IsNull(value)) { 
                    strValue = value.ToString();
                }

                if (altTextFormatString.Length > 0) { 
                    formattedAlternateText = String.Format(CultureInfo.CurrentCulture, altTextFormatString, value);
                } 
                else { 
                    formattedAlternateText = strValue;
                } 
            }
            else {
                formattedAlternateText = AlternateText;
            } 
            return formattedAlternateText;
        } 
 
        /// 
        /// Returns a value to be used for design-time rendering 
        /// 
        protected virtual string GetDesignTimeValue() {
            return SR.GetString(SR.Sample_Databound_Text);
        } 

        ///  
        /// Retrieves the value of the field to be databound to the ImageField. 
        /// 
        protected virtual object GetValue(Control controlContainer, string fieldName, ref PropertyDescriptor cachedDescriptor) { 
            Debug.Assert(DataImageUrlField.Length != 0, "Shouldn't be DataBinding without an DataImageUrlField");

            object data = null;
            object dataItem = null; 

            if (controlContainer == null) { 
                throw new HttpException(SR.GetString(SR.DataControlField_NoContainer)); 
            }
 
            // Get the DataItem from the container
            dataItem = DataBinder.GetDataItem(controlContainer);

            if (dataItem == null && !DesignMode) { 
                throw new HttpException(SR.GetString(SR.DataItem_Not_Found));
            } 
            // Get value of field in data item 
            if (cachedDescriptor == null) {
                if (!fieldName.Equals(ThisExpression)) { 
                    cachedDescriptor = TypeDescriptor.GetProperties(dataItem).Find(fieldName, true);
                    if ((cachedDescriptor == null) && !DesignMode) {
                        throw new HttpException(SR.GetString(SR.Field_Not_Found, fieldName));
                    } 
                }
            } 
 
            if (cachedDescriptor != null && dataItem != null) {
                data = cachedDescriptor.GetValue(dataItem); 
            }
            else {
                if (!DesignMode) {
                    data = dataItem; 
                }
            } 
 
            return data;
        } 

        /// 
        /// Initializes the field and resets member variables.
        ///  
        public override bool Initialize(bool enableSorting, Control control) {
            base.Initialize(enableSorting, control); 
            _imageFieldDesc = null; 
            _altTextFieldDesc = null;
 
            return false;
        }

        ///  
        /// Initializes a cell in the DataControlField.
        ///  
        public override void InitializeCell(DataControlFieldCell cell, DataControlCellType cellType, DataControlRowState rowState, int rowIndex) { 
            base.InitializeCell(cell, cellType, rowState, rowIndex);
 
            switch (cellType) {
                case DataControlCellType.DataCell:
                    InitializeDataCell(cell, rowState);
                    break; 
            }
        } 
 
        protected virtual void InitializeDataCell(DataControlFieldCell cell, DataControlRowState rowState) {
            Control boundControl = null; 

            if (((rowState & DataControlRowState.Edit) != 0 && ReadOnly == false) || (rowState & DataControlRowState.Insert) != 0) {
                TextBox editor = new TextBox();
                cell.Controls.Add(editor); 

                if (DataImageUrlField.Length != 0 && (rowState & DataControlRowState.Edit) != 0) { 
                    boundControl = editor; 
                }
            } 
            else if (DataImageUrlField.Length != 0) {
                boundControl = cell;
                Image image = new Image();
                Label label = new Label(); 
                cell.Controls.Add(image);
                cell.Controls.Add(label); 
            } 

            if (boundControl != null && Visible) { 
                boundControl.DataBinding += new EventHandler(this.OnDataBindField);
            }
        }
 
        /// 
        /// Handles databinding the field and its controls. 
        ///  
        protected virtual void OnDataBindField(object sender, EventArgs e) {
            Control boundControl = (Control)sender; 
            Control controlContainer = boundControl.NamingContainer;
            string urlValue = null;
            string nullImageUrl = NullImageUrl;
            string altText = GetFormattedAlternateText(controlContainer); 

            if (DesignMode && (boundControl is TableCell)) { 
                if (boundControl.Controls.Count == 0 || !(boundControl.Controls[0] is Image)) { 
                    throw new HttpException(SR.GetString(SR.ImageField_WrongControlType, DataImageUrlField));
                } 
                ((Image)boundControl.Controls[0]).Visible = false;
                ((TableCell)boundControl).Text = GetDesignTimeValue();
                return;
            } 

            object data = GetValue(controlContainer, DataImageUrlField, ref _imageFieldDesc); 
 
            urlValue = FormatImageUrlValue(data);
            if (boundControl is TableCell) {    // read-only 
                TableCell cell = (TableCell)boundControl;
                if (cell.Controls.Count < 2 || !(cell.Controls[0] is Image) || !(cell.Controls[1] is Label)) {
                    throw new HttpException(SR.GetString(SR.ImageField_WrongControlType, DataImageUrlField));
                } 
                Image image = (Image)cell.Controls[0];
                Label label = (Label)cell.Controls[1]; 
 
                label.Visible = false;
                if (urlValue == null || (ConvertEmptyStringToNull && urlValue.Length == 0)) { 
                    if (nullImageUrl.Length > 0) {
                        urlValue = nullImageUrl;
                    }
                    else { 
                        image.Visible = false;
                        label.Text = NullDisplayText; 
                        label.Visible = true; 
                    }
                } 
                if (!CrossSiteScriptingValidation.IsDangerousUrl(urlValue)) {
                    image.ImageUrl = urlValue;
                }
                image.AlternateText = altText; 
            }
            else {  // edit/insert 
                if (!(boundControl is TextBox)) { 
                    throw new HttpException(SR.GetString(SR.ImageField_WrongControlType, DataImageUrlField));
                } 
                ((TextBox)boundControl).Text = data.ToString();
                ((TextBox)boundControl).ToolTip = altText;

                if (data != null) { 
                    // size down the textbox for certain types
                    if (data.GetType().IsPrimitive) { 
                        ((TextBox)boundControl).Columns = 5; 
                    }
                } 
            }
        }

        ///  
        /// Override with an empty body if the field's controls all support callback.
        ///  Otherwise, override and throw a useful error message about why the field can't support callbacks. 
        ///  
        public override void ValidateSupportsCallback() {
        } 
    }
}


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
//------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Web.UI.WebControls { 
 
    using System;
    using System.Collections; 
    using System.Collections.Specialized;
    using System.ComponentModel;
    using System.Drawing.Design;
    using System.Globalization; 
    using System.IO;
    using System.Security.Permissions; 
    using System.Web.Util; 

    ///  
    /// Creates a field bounded to a data field in a .
    /// 
    [AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.Minimal)]
    [AspNetHostingPermission(SecurityAction.InheritanceDemand, Level=AspNetHostingPermissionLevel.Minimal)] 
    public class ImageField : DataControlField {
 
        ///  
        ///    Specifies a string that represents "this". This field is read-only. 
        ///  
        public static readonly string ThisExpression = "!";

        private PropertyDescriptor _imageFieldDesc;
        private PropertyDescriptor _altTextFieldDesc; 
        string _dataField;
 
        ///  
        /// Initializes a new instance of a  class.
        ///  
        public ImageField() {
        }

        [ 
        Localizable(true),
        WebCategory("Appearance"), 
        DefaultValue(""), 
        WebSysDescription(SR.ImageField_AlternateText)
        ] 
        public virtual string AlternateText {
            get {
                object o = ViewState["AlternateText"];
                if (o != null) { 
                    return (string)o;
                } 
                return String.Empty; 
            }
            set { 
                if (!String.Equals(value, ViewState["AlternateText"])) {
                    ViewState["AlternateText"] = value;
                    OnFieldChanged();
                } 
            }
        } 
 
        /// 
        ///    Gets or sets the property that determines whether the field treats empty string as 
        ///    null when the field values are extracted.
        /// 
        [
            WebCategory("Behavior"), 
            DefaultValue(true),
            WebSysDescription(SR.ImageField_ConvertEmptyStringToNull) 
        ] 
        public virtual bool ConvertEmptyStringToNull {
            get { 
                object o = ViewState["ConvertEmptyStringToNull"];
                if (o != null) {
                    return (bool)o;
                } 
                return true;
            } 
            set { 
                ViewState["ConvertEmptyStringToNull"] = value;
            } 
        }

        [
        WebCategory("Data"), 
        DefaultValue(""),
        TypeConverter("System.Web.UI.Design.DataSourceViewSchemaConverter, " + AssemblyRef.SystemDesign), 
        WebSysDescription(SR.ImageField_DataAlternateTextField) 
        ]
        public virtual string DataAlternateTextField { 
            get {
                object o = ViewState["DataAlternateTextField"];
                if (o != null) {
                    return (string)o; 
                }
                return String.Empty; 
            } 
            set {
                if (!String.Equals(value, ViewState["DataAlternateTextField"])) { 
                    ViewState["DataAlternateTextField"] = value;
                    OnFieldChanged();
                }
            } 
        }
 
        ///  
        ///    Gets or sets the display format of alternate text in this
        ///       field. 
        /// 
        [
        WebCategory("Data"),
        DefaultValue(""), 
        WebSysDescription(SR.ImageField_DataAlternateTextFormatString)
        ] 
        public virtual string DataAlternateTextFormatString { 
            get {
                object o = ViewState["DataAlternateTextFormatString"]; 
                if (o != null)
                    return (string)o;
                return String.Empty;
            } 
            set {
                if (!String.Equals(value, ViewState["DataAlternateTextFormatString"])) { 
                    ViewState["DataAlternateTextFormatString"] = value; 
                    OnFieldChanged();
                } 
            }
        }

        ///  
        ///     Gets or sets the field name from the data model bound to this field.
        ///  
        [ 
        WebCategory("Data"),
        DefaultValue(""), 
        TypeConverter("System.Web.UI.Design.DataSourceViewSchemaConverter, " + AssemblyRef.SystemDesign),
        WebSysDescription(SR.ImageField_ImageUrlField)
        ]
        public virtual string DataImageUrlField { 
            get {
                if (_dataField == null) { 
                    object o = ViewState["DataImageUrlField"]; 
                    if (o != null)
                        _dataField = (string)o; 
                    else
                        _dataField = String.Empty;
                    }
                return _dataField; 
            }
            set { 
                if (!String.Equals(value, ViewState["DataImageUrlField"])) { 
                    ViewState["DataImageUrlField"] = value;
                    _dataField = value; 
                    OnFieldChanged();
                }
            }
        } 

        [ 
        WebCategory("Data"), 
        DefaultValue(""),
        WebSysDescription(SR.ImageField_ImageUrlFormatString) 
        ]
        public virtual string DataImageUrlFormatString {
            get {
                object o = ViewState["DataImageUrlFormatString"]; 
                if (o != null) {
                    return (string)o; 
                } 
                return String.Empty;
            } 
            set {
                if (!String.Equals(value, ViewState["DataImageUrlFormatString"])) {
                    ViewState["DataImageUrlFormatString"] = value;
                    OnFieldChanged(); 
                }
            } 
        } 

        ///  
        ///    Gets or sets the property that determines what text is displayed if the value
        ///    of the field is null.
        /// 
        [ 
        Localizable(true),
        WebCategory("Behavior"), 
        DefaultValue(""), 
        WebSysDescription(SR.BoundField_NullDisplayText)
        ] 
        public virtual string NullDisplayText {
            get {
                object o = ViewState["NullDisplayText"];
                if (o != null) { 
                    return (string)o;
                } 
                return String.Empty; 
            }
            set { 
                if (!String.Equals(value, ViewState["NullDisplayText"])) {
                    ViewState["NullDisplayText"] = value;
                    OnFieldChanged();
                } 
            }
        } 
 
        [
        WebCategory("Behavior"), 
        DefaultValue(""),
        Editor("System.Web.UI.Design.ImageUrlEditor, " + AssemblyRef.SystemDesign, typeof(UITypeEditor)),
        UrlProperty(),
        WebSysDescription(SR.ImageField_NullImageUrl) 
        ]
        public virtual string NullImageUrl { 
            get { 
                object o = ViewState["NullImageUrl"];
                if (o != null) { 
                    return (string)o;
                }
                return String.Empty;
            } 
            set {
                if (!String.Equals(value, ViewState["NullImageUrl"])) { 
                    ViewState["NullImageUrl"] = value; 
                    OnFieldChanged();
                } 
            }
        }

        ///  
        ///    Gets or sets the property that prevents modification to data
        ///       in this field. 
        ///  
        [
        WebCategory("Behavior"), 
        DefaultValue(false),
        WebSysDescription(SR.ImageField_ReadOnly)
        ]
        public virtual bool ReadOnly { 
            get {
                object o = ViewState["ReadOnly"]; 
                if (o != null) 
                    return (bool)o;
                return false; 
            }
            set {
                object oldValue = ViewState["ReadOnly"];
                if (oldValue == null || (bool)oldValue != value) { 
                    ViewState["ReadOnly"] = value;
                    OnFieldChanged(); 
                } 
            }
        } 

        protected override void CopyProperties(DataControlField newField) {
            ((ImageField)newField).AlternateText = AlternateText;
            ((ImageField)newField).ConvertEmptyStringToNull = ConvertEmptyStringToNull; 
            ((ImageField)newField).DataAlternateTextField = DataAlternateTextField;
            ((ImageField)newField).DataAlternateTextFormatString = DataAlternateTextFormatString; 
            ((ImageField)newField).DataImageUrlField = DataImageUrlField; 
            ((ImageField)newField).DataImageUrlFormatString = DataImageUrlFormatString;
            ((ImageField)newField).NullDisplayText = NullDisplayText; 
            ((ImageField)newField).NullImageUrl = NullImageUrl;
            ((ImageField)newField).ReadOnly = ReadOnly;
            base.CopyProperties(newField);
        } 

        protected override DataControlField CreateField() { 
            return new ImageField(); 
        }
 
        /// 
        /// Extracts the value(s) from the given cell and puts the value(s) into a dictionary.  Indicate includeReadOnly
        /// to have readonly fields' values inserted into the dictionary.
        ///  
        public override void ExtractValuesFromCell(IOrderedDictionary dictionary, DataControlFieldCell cell, DataControlRowState rowState, bool includeReadOnly) {
            Control childControl = null; 
            string dataField = DataImageUrlField; 
            object value = null;
            bool includeNullValue = false; 

            if (((rowState & DataControlRowState.Insert) != 0) && !InsertVisible) {
                return;
            } 

            if (cell.Controls.Count == 0) { // this should happen only in design mode 
                Debug.Assert(DesignMode, "Unless you're in designmode, there should be a control in the cell."); 
                return;
            } 

            childControl = cell.Controls[0];

            Image image = childControl as Image; 
            if (image != null) {
                if (includeReadOnly) { 
                    includeNullValue = true; 
                    if (image.Visible) {
                        value = image.ImageUrl; 
                    }
                }
            }
            else { 
                TextBox editBox = childControl as TextBox;
                if (editBox != null) { 
                    value = editBox.Text; 
                    includeNullValue = true;    // just in case someone wrote a derived textbox that returns null for Text.
                } 
            }

            if (value != null || includeNullValue) {
                if (ConvertEmptyStringToNull && value is string && ((string)value).Length == 0) { 
                    value = null;
                } 
 
                if (dictionary.Contains(dataField)) {
                    dictionary[dataField] = value; 
                }
                else {
                    dictionary.Add(dataField, value);
                } 
            }
        } 
 
        /// 
        /// Returns the formatted value of the image url 
        /// 
        protected virtual string FormatImageUrlValue(object dataValue) {
            string formattedValue = String.Empty;
            string formatting = DataImageUrlFormatString; 

            if (!DataBinder.IsNull(dataValue)) { 
                string dataValueString = dataValue.ToString(); 

                if (dataValueString.Length > 0) { 
                    if (formatting.Length == 0) {
                        formattedValue = dataValueString;
                    }
                    else { 
                        formattedValue = String.Format(CultureInfo.CurrentCulture, formatting, dataValue);
                    } 
                } 
            }
            else { 
                return null;
            }
            return formattedValue;
        } 

        ///  
        /// Returns the alternate text to be used for accessibility 
        /// 
        protected virtual string GetFormattedAlternateText(Control controlContainer) { 
            string altTextField = DataAlternateTextField;
            string altTextFormatString = DataAlternateTextFormatString;
            string formattedAlternateText;
 

            if (altTextField.Length > 0) { 
                object value = GetValue(controlContainer, altTextField, ref _altTextFieldDesc); 
                string strValue = String.Empty;
                if (!DataBinder.IsNull(value)) { 
                    strValue = value.ToString();
                }

                if (altTextFormatString.Length > 0) { 
                    formattedAlternateText = String.Format(CultureInfo.CurrentCulture, altTextFormatString, value);
                } 
                else { 
                    formattedAlternateText = strValue;
                } 
            }
            else {
                formattedAlternateText = AlternateText;
            } 
            return formattedAlternateText;
        } 
 
        /// 
        /// Returns a value to be used for design-time rendering 
        /// 
        protected virtual string GetDesignTimeValue() {
            return SR.GetString(SR.Sample_Databound_Text);
        } 

        ///  
        /// Retrieves the value of the field to be databound to the ImageField. 
        /// 
        protected virtual object GetValue(Control controlContainer, string fieldName, ref PropertyDescriptor cachedDescriptor) { 
            Debug.Assert(DataImageUrlField.Length != 0, "Shouldn't be DataBinding without an DataImageUrlField");

            object data = null;
            object dataItem = null; 

            if (controlContainer == null) { 
                throw new HttpException(SR.GetString(SR.DataControlField_NoContainer)); 
            }
 
            // Get the DataItem from the container
            dataItem = DataBinder.GetDataItem(controlContainer);

            if (dataItem == null && !DesignMode) { 
                throw new HttpException(SR.GetString(SR.DataItem_Not_Found));
            } 
            // Get value of field in data item 
            if (cachedDescriptor == null) {
                if (!fieldName.Equals(ThisExpression)) { 
                    cachedDescriptor = TypeDescriptor.GetProperties(dataItem).Find(fieldName, true);
                    if ((cachedDescriptor == null) && !DesignMode) {
                        throw new HttpException(SR.GetString(SR.Field_Not_Found, fieldName));
                    } 
                }
            } 
 
            if (cachedDescriptor != null && dataItem != null) {
                data = cachedDescriptor.GetValue(dataItem); 
            }
            else {
                if (!DesignMode) {
                    data = dataItem; 
                }
            } 
 
            return data;
        } 

        /// 
        /// Initializes the field and resets member variables.
        ///  
        public override bool Initialize(bool enableSorting, Control control) {
            base.Initialize(enableSorting, control); 
            _imageFieldDesc = null; 
            _altTextFieldDesc = null;
 
            return false;
        }

        ///  
        /// Initializes a cell in the DataControlField.
        ///  
        public override void InitializeCell(DataControlFieldCell cell, DataControlCellType cellType, DataControlRowState rowState, int rowIndex) { 
            base.InitializeCell(cell, cellType, rowState, rowIndex);
 
            switch (cellType) {
                case DataControlCellType.DataCell:
                    InitializeDataCell(cell, rowState);
                    break; 
            }
        } 
 
        protected virtual void InitializeDataCell(DataControlFieldCell cell, DataControlRowState rowState) {
            Control boundControl = null; 

            if (((rowState & DataControlRowState.Edit) != 0 && ReadOnly == false) || (rowState & DataControlRowState.Insert) != 0) {
                TextBox editor = new TextBox();
                cell.Controls.Add(editor); 

                if (DataImageUrlField.Length != 0 && (rowState & DataControlRowState.Edit) != 0) { 
                    boundControl = editor; 
                }
            } 
            else if (DataImageUrlField.Length != 0) {
                boundControl = cell;
                Image image = new Image();
                Label label = new Label(); 
                cell.Controls.Add(image);
                cell.Controls.Add(label); 
            } 

            if (boundControl != null && Visible) { 
                boundControl.DataBinding += new EventHandler(this.OnDataBindField);
            }
        }
 
        /// 
        /// Handles databinding the field and its controls. 
        ///  
        protected virtual void OnDataBindField(object sender, EventArgs e) {
            Control boundControl = (Control)sender; 
            Control controlContainer = boundControl.NamingContainer;
            string urlValue = null;
            string nullImageUrl = NullImageUrl;
            string altText = GetFormattedAlternateText(controlContainer); 

            if (DesignMode && (boundControl is TableCell)) { 
                if (boundControl.Controls.Count == 0 || !(boundControl.Controls[0] is Image)) { 
                    throw new HttpException(SR.GetString(SR.ImageField_WrongControlType, DataImageUrlField));
                } 
                ((Image)boundControl.Controls[0]).Visible = false;
                ((TableCell)boundControl).Text = GetDesignTimeValue();
                return;
            } 

            object data = GetValue(controlContainer, DataImageUrlField, ref _imageFieldDesc); 
 
            urlValue = FormatImageUrlValue(data);
            if (boundControl is TableCell) {    // read-only 
                TableCell cell = (TableCell)boundControl;
                if (cell.Controls.Count < 2 || !(cell.Controls[0] is Image) || !(cell.Controls[1] is Label)) {
                    throw new HttpException(SR.GetString(SR.ImageField_WrongControlType, DataImageUrlField));
                } 
                Image image = (Image)cell.Controls[0];
                Label label = (Label)cell.Controls[1]; 
 
                label.Visible = false;
                if (urlValue == null || (ConvertEmptyStringToNull && urlValue.Length == 0)) { 
                    if (nullImageUrl.Length > 0) {
                        urlValue = nullImageUrl;
                    }
                    else { 
                        image.Visible = false;
                        label.Text = NullDisplayText; 
                        label.Visible = true; 
                    }
                } 
                if (!CrossSiteScriptingValidation.IsDangerousUrl(urlValue)) {
                    image.ImageUrl = urlValue;
                }
                image.AlternateText = altText; 
            }
            else {  // edit/insert 
                if (!(boundControl is TextBox)) { 
                    throw new HttpException(SR.GetString(SR.ImageField_WrongControlType, DataImageUrlField));
                } 
                ((TextBox)boundControl).Text = data.ToString();
                ((TextBox)boundControl).ToolTip = altText;

                if (data != null) { 
                    // size down the textbox for certain types
                    if (data.GetType().IsPrimitive) { 
                        ((TextBox)boundControl).Columns = 5; 
                    }
                } 
            }
        }

        ///  
        /// Override with an empty body if the field's controls all support callback.
        ///  Otherwise, override and throw a useful error message about why the field can't support callbacks. 
        ///  
        public override void ValidateSupportsCallback() {
        } 
    }
}


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
                        

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