DataFieldConverter.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / MIT / System / Web / UI / MobileControls / Design / Converters / DataFieldConverter.cs / 1305376 / DataFieldConverter.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Web.UI.Design.MobileControls.Converters 
{ 
    using System;
    using System.Collections; 
    using System.ComponentModel;
    using System.ComponentModel.Design;
    using System.Data;
    using System.Diagnostics; 
    using System.Runtime.InteropServices;
    using System.Globalization; 
    using System.Web.UI.Design; 
    using System.Web.UI.MobileControls;
    using System.Security.Permissions; 

    /// 
    /// 
    ///     
    ///       Provides design-time support for a component's data field properties.
    ///     
    ///  
    [
        System.Security.Permissions.SecurityPermission(System.Security.Permissions.SecurityAction.Demand, 
        Flags=System.Security.Permissions.SecurityPermissionFlag.UnmanagedCode)
    ]
    [AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.Minimal)]
    [AspNetHostingPermission(SecurityAction.InheritanceDemand, Level=AspNetHostingPermissionLevel.Minimal)] 
    [Obsolete("The System.Web.Mobile.dll assembly has been deprecated and should no longer be used. For information about how to develop ASP.NET mobile applications, see http://go.microsoft.com/fwlink/?LinkId=157231.")]
    public class DataFieldConverter : TypeConverter 
    { 
        private const String _dataMemberPropertyName = "DataMember";
        private const String _dataSourcePropertyName = "DataSource"; 

        /// 
        /// 
        ///     
        ///       Initializes a new instance of .
        ///     
        ///  
        public DataFieldConverter()
        { 
        }

        /// 
        ///  
        ///    
        ///       Gets a value indicating whether this converter can 
        ///       convert an object in the given source type to the native type of the converter 
        ///       using the context.
        ///     
        /// 
        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        {
            if (sourceType == typeof(string)) 
            {
                return true; 
            } 
            return false;
        } 

        /// 
        /// 
        ///     
        ///       Converts the given object to the converter's native type.
        ///     
        ///  
        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
        { 
            if (value == null)
            {
                return String.Empty;
            } 
            else if (value.GetType() == typeof(string))
            { 
                return (string)value; 
            }
            throw GetConvertFromException(value); 
        }

        /// 
        ///  
        ///    
        ///       Gets the fields present within the selected data source if information about them is available. 
        ///     
        /// 
        public override StandardValuesCollection GetStandardValues(ITypeDescriptorContext context) 
        {
            object[] names = null;
            String dataMember = null;
            bool autoGenerateFields = false; 
            bool autoGenerateFieldsSet = false;
            ObjectList objectList = null; 
 
            if (context != null)
            { 
                ArrayList list = new ArrayList();

                PropertyDescriptorCollection props = null;
 
                IComponent component = context.Instance as IComponent;
                if (component is IDeviceSpecificChoiceDesigner) 
                { 
                    Object owner = ((ChoicePropertyFilter)component).Owner;
                    PropertyDescriptor pd = 
                        ((ICustomTypeDescriptor)component).GetProperties()[_dataMemberPropertyName];
                    Debug.Assert(pd != null, "Cannot get DataMember");

                    if (owner is ObjectList) 
                    {
                        autoGenerateFields = ((ObjectList)owner).AutoGenerateFields; 
                        autoGenerateFieldsSet = true; 
                    }
 
                    component = ((IDeviceSpecificChoiceDesigner)component).UnderlyingControl;

                    // See if owner already has a DataMember
                    dataMember = (String)pd.GetValue(owner); 
                    Debug.Assert(dataMember != null);
                    if (dataMember != null && dataMember.Length == 0) 
                    { 
                        // Get it from underlying object.
                        dataMember = (String)pd.GetValue(component); 
                        Debug.Assert(dataMember != null);
                    }
                }
 
                if (component != null)
                { 
                    objectList = component as ObjectList; 

                    if (objectList != null) 
                    {
                        foreach(ObjectListField field in objectList.Fields)
                        {
                            list.Add(field.Name); 
                        }
 
                        if (!autoGenerateFieldsSet) 
                        {
                            autoGenerateFields = objectList.AutoGenerateFields; 
                        }
                    }

                    if (objectList == null || autoGenerateFields) 
                    {
                        ISite componentSite = component.Site; 
                        if (componentSite != null) 
                        {
                            IDesignerHost designerHost = (IDesignerHost)componentSite.GetService(typeof(IDesignerHost)); 
                            if (designerHost != null)
                            {
                                IDesigner designer = designerHost.GetDesigner(component);
 
                                if (designer is IDataSourceProvider)
                                { 
                                    IEnumerable dataSource = null; 
                                    if (!String.IsNullOrEmpty(dataMember))
                                    { 
                                        DataBindingCollection dataBindings =
                                            ((HtmlControlDesigner)designer).DataBindings;
                                        DataBinding binding = dataBindings[_dataSourcePropertyName];
                                        if (binding != null) 
                                        {
                                            dataSource = 
                                                DesignTimeData.GetSelectedDataSource( 
                                                component,
                                                binding.Expression, 
                                                dataMember);
                                        }
                                    }
                                    else 
                                    {
                                        dataSource = 
                                            ((IDataSourceProvider)designer).GetResolvedSelectedDataSource(); 
                                    }
 
                                    if (dataSource != null)
                                    {
                                        props = DesignTimeData.GetDataFields(dataSource);
                                    } 
                                }
                            } 
                        } 
                    }
                } 

                if (props != null)
                {
                    foreach (PropertyDescriptor propDesc in props) 
                    {
                        list.Add(propDesc.Name); 
                    } 
                }
 
                names = list.ToArray();
                Array.Sort(names);
            }
            return new StandardValuesCollection(names); 
        }
 
        ///  
        /// 
        ///     
        ///       Gets a value indicating whether the collection of standard values returned from
        ///     is an exclusive
        ///       list of possible values, using the specified context.
        ///     
        /// 
        public override bool GetStandardValuesExclusive(ITypeDescriptorContext context) 
        { 
            return false;
        } 

        /// 
        /// 
        ///     
        ///       Gets a value indicating whether this object supports a standard set of values
        ///       that can be picked from a list. 
        ///     
        /// 
        public override bool GetStandardValuesSupported(ITypeDescriptorContext context) 
        {
            if (context.Instance is IComponent)
            {
                // We only support the dropdown in single-select mode. 
                return true;
            } 
            return false; 
        }
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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DataFieldConverter.cs source code in C# .NET

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