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/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / xsp / System / Web / UI / WebControls / CompositeDataBoundControl.cs / 1 / CompositeDataBoundControl.cs
//------------------------------------------------------------------------------ //// Copyright (c) Microsoft Corporation. All rights reserved. // //----------------------------------------------------------------------------- namespace System.Web.UI.WebControls { using System; using System.Collections; using System.Security.Permissions; [AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.Minimal)] [AspNetHostingPermission(SecurityAction.InheritanceDemand, Level=AspNetHostingPermissionLevel.Minimal)] public abstract class CompositeDataBoundControl : DataBoundControl, INamingContainer { internal const string ItemCountViewStateKey = "_!ItemCount"; public override ControlCollection Controls { get { EnsureChildControls(); return base.Controls; } } ////// Overriden by DataBoundControl to determine if the control should /// recreate its control hierarchy based on values in view state. /// If the control hierarchy should be created, i.e. view state does /// exist, it calls CreateChildControls with a dummy (empty) data source /// which is usable for enumeration purposes only. /// protected internal override void CreateChildControls() { Controls.Clear(); object controlCount = ViewState[ItemCountViewStateKey]; if (controlCount == null && RequiresDataBinding) { EnsureDataBound(); } if (controlCount != null && ((int)controlCount) != -1) { object[] dummyDataSource = new object[(int)controlCount]; CreateChildControls(dummyDataSource, false); ClearChildViewState(); } } ////// Performs the work of creating the control hierarchy based on a data source. /// When dataBinding is true, the specified data source contains real /// data, and the data is supposed to be pushed into the UI. /// When dataBinding is false, the specified data source is a dummy data /// source, that allows enumerating the right number of items, but the items /// themselves are null and do not contain data. In this case, the recreated /// control hierarchy reinitializes its state from view state. /// It enables a DataBoundControl to encapsulate the logic of creating its /// control hierarchy in both modes into a single code path. /// /// /// The data source to be used to enumerate items. /// /// /// Whether the method has been called from DataBind or not. /// ////// The number of items created based on the data source. Put another way, its /// the number of items enumerated from the data source. /// protected abstract int CreateChildControls(IEnumerable dataSource, bool dataBinding); ////// Overriden by DataBoundControl 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 DataSourceControlID takes highest precedence. /// In this mode, DataMember is used to access the appropriate list from the /// DataControl. /// If DataSourceControlID 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. /// protected internal override void PerformDataBinding(IEnumerable data) { base.PerformDataBinding(data); Controls.Clear(); ClearChildViewState(); TrackViewState(); int controlCount = CreateChildControls(data, true); ChildControlsCreated = true; ViewState[ItemCountViewStateKey] = controlCount; } } }
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