BaseDataBoundControl.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / xsp / System / Web / UI / WebControls / BaseDataBoundControl.cs / 1305376 / BaseDataBoundControl.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Web.UI.WebControls { 
 
    using System;
    using System.Collections; 
    using System.ComponentModel;
    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") 
    ]
    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); 
            } 
        }
 
        public override bool SupportsDisabledAttribute {
            get {
                return RenderingCompatibility < VersionUtil.Framework40;
            } 
        }
 
        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); 
    } 
}
 

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

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