BaseDataBoundControl.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / xsp / System / Web / UI / WebControls / BaseDataBoundControl.cs / 1 / BaseDataBoundControl.cs
                        

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

namespace System.Web.UI.WebControls { 
 
    using System;
    using System.Collections; 
    using System.ComponentModel;
    using System.Security.Permissions;
    using System.Web.Util;
 

    ///  
    /// A BaseDataBoundControl is bound to a data source and generates its 
    /// user interface (or child control hierarchy typically), by enumerating
    /// the items in the data source it is bound to. 
    /// BaseDataBoundControl is an abstract base class that defines the common
    /// characteristics of all controls that use a list as a data source, such as
    /// DataGrid, DataBoundTable, ListBox etc. It encapsulates the logic
    /// of how a data-bound control binds to collections or DataControl instances. 
    /// 
 
    [ 
    Designer("System.Web.UI.Design.WebControls.BaseDataBoundControlDesigner, " + AssemblyRef.SystemDesign),
    DefaultProperty("DataSourceID") 
    ]
    [AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.Minimal)]
    [AspNetHostingPermission(SecurityAction.InheritanceDemand, Level=AspNetHostingPermissionLevel.Minimal)]
    public abstract class BaseDataBoundControl : WebControl { 

        private static readonly object EventDataBound = new object(); 
 
        private object _dataSource;
        private bool _requiresDataBinding; 
        private bool _inited;
        private bool _preRendered;
        private bool _requiresBindToNull;
        private bool _throwOnDataPropertyChange; 

 
        ///  
        /// The data source to bind to. This allows a BaseDataBoundControl to bind
        /// to arbitrary lists of data items. 
        /// 
        [
        Bindable(true),
        DefaultValue(null), 
        DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden),
        Themeable(false), 
        WebCategory("Data"), 
        WebSysDescription(SR.BaseDataBoundControl_DataSource),
        ] 
        public virtual object DataSource {
            get {
                return _dataSource;
            } 
            set {
                if (value != null) { 
                    ValidateDataSource(value); 
                }
                _dataSource = value; 
                OnDataPropertyChanged();
            }
        }
 

        ///  
        /// The ID of the DataControl that this control should use to retrieve 
        /// its data source. When the control is bound to a DataControl, it
        /// can retrieve a data source instance on-demand, and thereby attempt 
        /// to work in auto-DataBind mode.
        /// 
        [
        DefaultValue(""), 
        Themeable(false),
        WebCategory("Data"), 
        WebSysDescription(SR.BaseDataBoundControl_DataSourceID) 
        ]
        public virtual string DataSourceID { 
            get {
                object o = ViewState["DataSourceID"];
                if (o != null) {
                    return (string)o; 
                }
                return String.Empty; 
            } 
            set {
                if (String.IsNullOrEmpty(value) && !String.IsNullOrEmpty(DataSourceID)) { 
                    _requiresBindToNull = true;
                }

                ViewState["DataSourceID"] = value; 
                OnDataPropertyChanged();
            } 
        } 

 
        protected bool Initialized {
            get {
                return _inited;
            } 
        }
 
 
        protected bool IsBoundUsingDataSourceID {
            get { 
                return (DataSourceID.Length > 0);
            }
        }
 

        protected bool RequiresDataBinding { 
            get { 
                return _requiresDataBinding;
            } 
            set {
                // if we have to play catch-up here because we've already PreRendered, call EnsureDataBound
                if (value && _preRendered && DataSourceID.Length > 0 && Page != null && !Page.IsCallback) {
                    _requiresDataBinding = true; 
                    EnsureDataBound();
                } 
                else { 
                    _requiresDataBinding = value;
                } 
            }
        }

 
        [
        WebCategory("Data"), 
        WebSysDescription(SR.BaseDataBoundControl_OnDataBound) 
        ]
        public event EventHandler DataBound { 
            add {
                Events.AddHandler(EventDataBound, value);
            }
            remove { 
                Events.RemoveHandler(EventDataBound, value);
            } 
        } 

        protected void ConfirmInitState() { 
            _inited = true; // do this in OnLoad in case we were added to the page after Page.OnPreLoad
        }

 
        /// 
        /// Overriden by BaseDataBoundControl to use its properties to determine the real 
        /// data source that the control should bind to. It then clears the existing 
        /// control hierarchy, and calls CreateChildControls to create a new control
        /// hierarchy based on the resolved data source. 
        /// The implementation resolves various data source related properties to
        /// arrive at the appropriate IEnumerable implementation to use as the real
        /// data source.
        /// When resolving data sources, the DataSourceID takes highest precedence. 
        /// If DataSourceID is not set, the value of the DataSource property is used.
        /// In this second alternative, DataMember is used to extract the appropriate 
        /// list if the control has been handed an IListSource as a data source. 
        ///
        /// Data bound controls should override PerformDataBinding instead 
        /// of DataBind.  If DataBind if overridden, the OnDataBinding and OnDataBound events will
        /// fire in the wrong order.  However, for backwards compat on ListControl and AdRotator, we
        /// can't seal this method.  It is sealed on all new BaseDataBoundControl-derived controls.
        ///  
        public override void DataBind() {
            // Don't databind when the control is in the designer but not top-level 
            if (DesignMode) { 
                IDictionary designModeState = GetDesignModeState();
                if (((designModeState == null) || (designModeState["EnableDesignTimeDataBinding"] == null)) 
                    && (Site == null)) {
                    return;
                }
            } 

            PerformSelect(); 
        } 

 
        protected virtual void EnsureDataBound() {
            try {
                _throwOnDataPropertyChange = true;
                if (RequiresDataBinding && (DataSourceID.Length > 0 || _requiresBindToNull)) { 
                    DataBind();
                    _requiresBindToNull = false; 
                } 
            }
            finally { 
                _throwOnDataPropertyChange = false;
            }
        }
 

        protected virtual void OnDataBound(EventArgs e) { 
            EventHandler handler = Events[EventDataBound] as EventHandler; 
            if (handler != null) {
                handler(this, e); 
            }
        }

 
        /// 
        ///  This method is called when DataMember, DataSource, or DataSourceID is changed. 
        ///  
        protected virtual void OnDataPropertyChanged() {
            if (_throwOnDataPropertyChange) { 
                throw new HttpException(SR.GetString(SR.DataBoundControl_InvalidDataPropertyChange, ID));
            }
            if (_inited) {
                RequiresDataBinding = true; 
            }
        } 
 

        protected internal override void OnInit(EventArgs e) { 
            base.OnInit(e);

            if (Page != null) {
                Page.PreLoad += new EventHandler(this.OnPagePreLoad); 

                if (!IsViewStateEnabled && Page.IsPostBack) { 
                    RequiresDataBinding = true; 
                }
            } 
        }

        protected virtual void OnPagePreLoad(object sender, EventArgs e) {
            _inited = true; 
            if (Page != null) {
                Page.PreLoad -= new EventHandler(this.OnPagePreLoad); 
            } 
        }
 

        protected internal override void OnPreRender(EventArgs e) {
            _preRendered = true;
            EnsureDataBound(); 
            base.OnPreRender(e);
        } 
 
        /// 
        /// Override to control how the data is selected and the control is databound. 
        /// 
        protected abstract void PerformSelect();

 
        protected abstract void ValidateDataSource(object dataSource);
    } 
}

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