-----------------------------------------------------------
New Message on BDOTNET
-----------------------------------------------------------
From: cutespn
Message 4 in Discussion
Hi Kalyan, I too faced same problem with Placeholder,the reason is that place holder
by default doesnt have ViewState,we have to explicitly write a class to attain this.
Pls find the code below this message. Hope this solves ur problem sudheer.
using System;
using System.Collections;
using System.Reflection;
using System.Web;
using System.Web.UI;
using System.Web.UI.Design;
using System.Web.UI.Design.WebControls;
using System.Web.UI.WebControls;
using System.ComponentModel;
namespace Common.Program
{
/// <summary>
/// ViewStatePlaceholder solves the problem that dynamically added controls are not
automatically recreated on subsequent requests
/// The controls uses the ViewState to store the types of the child controls
recursively and recreates them automatically.
///
/// Please note that property values that are set before "TrackViewState" is called
(usually in Controls.Add) are not persisted
/// </summary>
[ControlBuilder(typeof(System.Web.UI.WebControls.PlaceHolderControlBuilder)),
Designer("System.Web.UI.Design.ControlDesigner"),
DefaultProperty("ID"),
ToolboxData("<{0}:ViewStatePlaceholder runat=server></{0}:ViewStatePlaceholder>")]
public class ViewStatePlaceholder : PlaceHolder
{
#region custom events
/// <summary>
/// Occurs when a control has been restored from ViewState
/// </summary>
public event DynamicControlEventHandler ControlRestored;
/// <summary>
/// Occurs when the ViewStatePlaceholder is about to restore the child controls from
ViewState
/// </summary>
public event EventHandler PreRestore;
/// <summary>
/// Occurs after the ViewStatePlaceholder has restored the child controls from
ViewState
/// </summary>
public event EventHandler PostRestore;
/// <summary>
/// Raises the <see cref="ControlRestored">ControlRestored</see> event.
/// </summary>
/// <param name="e">The <see
cref="DynamicControlEventArgs">DynamicControlEventArgs</see> object that contains the
event data.</param>
protected virtual void OnControlRestored(DynamicControlEventArgs e)
{
if(ControlRestored != null)
ControlRestored(this, e);
}
/// <summary>
/// Raises the <see cref="PreRestore">PreRestore</see> event.
/// </summary>
/// <param name="e">The <see cref="System.EventArgs">EventArgs</see> object that
contains the event data.</param>
protected virtual void OnPreRestore(EventArgs e)
{
if(PreRestore != null)
PreRestore(this, e);
}
/// <summary>
/// Raises the <see cref="PostRestore">PostRestore</see> event.
/// </summary>
/// <param name="e">The <see cref="System.EventArgs">EventArgs</see> object that
contains the event data.</param>
protected virtual void OnPostRestore(EventArgs e)
{
if(PostRestore != null)
PostRestore(this, e);
}
#endregion custom events
#region custom propterties
/// <summary>
/// Specifies whether Controls without IDs shall be persisted or if an exception shall
be thrown
/// </summary>
[DefaultValue(HandleDynamicControls.DontPersist)]
public HandleDynamicControls ControlsWithoutIDs
{
get
{
if(ViewState["ControlsWithoutIDs"] == null)
return HandleDynamicControls.DontPersist;
else
return (HandleDynamicControls) ViewState["ControlsWithoutIDs"];
}
set { ViewState["ControlsWithoutIDs"] = value; }
}
#endregion custom propterties
#region ViewState management
/// <summary>
/// Recreates all dynamically added child controls of the Placeholder and then calls
the default
/// LoadViewState mechanism
/// </summary>
/// <param name="savedState">Array of objects that contains the child structure in the
first item,
/// and the base ViewState in the second item</param>
protected override void LoadViewState(object savedState)
{
object[] viewState = (object[]) savedState;
//Raise PreRestore event
OnPreRestore(EventArgs.Empty);
//recreate the child controls recursively
Pair persistInfo = (Pair) viewState[0];
foreach(Pair pair in (ArrayList) persistInfo.Second)
{
RestoreChildStructure(pair, this);
}
//Raise PostRestore event
OnPostRestore(EventArgs.Empty);
base.LoadViewState(viewState[1]);
}
/// <summary>
/// Walks recursively through all child controls and stores their type in ViewState
and then calls the default
/// SaveViewState mechanism
/// </summary>
/// <returns>Array of objects that contains the child structure in the first item,
/// and the base ViewState in the second item</returns>
protected override object SaveViewState()
{
if(HttpContext.Current == null)
return null;
object[] viewState = new object[2];
viewState[0] = PersistChildStructure(this, "C");
viewState[1] = base.SaveViewState();
return viewState;
}
/// <summary>
/// Recreates a single control and recursively calls itself for all child controls
/// </summary>
/// <param name="persistInfo">A pair that contains the controls persisted information
in the first property,
/// and an ArrayList with the child's persisted information in the second
property</param>
/// <param name="parent">The parent control to which Controls collection it is
added</param>
private void RestoreChildStructure(Pair persistInfo, Control parent)
{
Control control;
string[] persistedString = persistInfo.First.ToString().Split(';');
string[] typeName = persistedString[1].Split(':');
switch(typeName[0])
{
//restore the UserControl by calling Page.LoadControl
case "UC":
//recreate the Filename from the Typename
string ucFilename = typeName[2] + "/" + typeName[1].Split('.')[1].Replace("_", ".");
control = Page.LoadControl(ucFilename);
break;
case "C":
//create a new instance of the control's type
Type type = Type.GetType(typeName[1], true, true);
try
{
control = (Control) Activator.CreateInstance(type);
}
catch(Exception e)
{
throw new ArgumentException(String.Format("The type '{0}' cannot be recreated from
ViewState", type.ToString()), e);
}
break;
default:
throw new ArgumentException("Unknown type - cannot recreate from ViewState");
}
control.ID = persistedString[2];
switch(persistedString[0])
{
//adding control to "Controls" collection
case "C":
parent.Controls.Add(control);
break;
}
//Raise OnControlRestoredEvent
OnControlRestored(new DynamicControlEventArgs(control));
//recreate all the child controls
foreach(Pair pair in (ArrayList) persistInfo.Second)
{
RestoreChildStructure(pair, control);
}
}
/// <summary>
/// Saves a single control and recursively calls itself to save all child controls
/// </summary>
/// <param name="control">reference to the control</param>
/// <param name="controlCollectionName">contains an abbreviation to indicate to which
control collection the control belongs</param>
/// <returns>A pair that contains the controls persisted information in the first
property,
/// and an ArrayList with the child's persisted information in the second
property</returns>
private Pair PersistChildStructure(Control control, string controlCollectionName)
{
string typeName;
ArrayList childPersistInfo = new ArrayList();
//check if the control has an ID
if(control.ID == null)
{
if(ControlsWithoutIDs == HandleDynamicControls.ThrowException)
throw new NotSupportedException("ViewStatePlaceholder does not support child controls
whose ID is not set, as this may have unintended side effects: " +
control.GetType().ToString());
else if (ControlsWithoutIDs == HandleDynamicControls.DontPersist)
return null;
}
if(control is UserControl)
typeName = "UC:" + ((UserControl) control).GetType().ToString() + ":" +
control.TemplateSourceDirectory;
else
typeName = "C:" + control.GetType().AssemblyQualifiedName;
string persistedString = controlCollectionName + ";" + typeName + ";" + control.ID;
//childs of a UserControl need not be saved as they are recreated on Page.LoadControl
if(!(control is UserControl))
{
//saving all child controls from "Controls" collection
for(int counter = 0; counter < control.Controls.Count; counter++)
{
Control child = control.Controls[counter];
Pair pair = PersistChildStructure(child, "C");
if(pair != null)
childPersistInfo.Add(pair);
}
}
return new Pair(persistedString, childPersistInfo);
}
#endregion ViewState management
#region Render method
/// <summary>
/// Renders a copyright box in design mode and calls the base method at runtime
/// </summary>
/// <param name="writer"></param>
protected override void Render(System.Web.UI.HtmlTextWriter writer)
{
if(HttpContext.Current == null)
{
System.Web.UI.Design.ControlDesigner cd = new System.Web.UI.Design.ControlDesigner();
//create a dummy instance that System.Design.DLL is included as a reference
string designTimeHTML = "<p style=\"font-family: verdana; color: #FFFFFF; font-size:
xx-small; border: outset 1px #000000; padding: 10 10 10 10; background-color:
#0033ff\">" +
"<b>ViewStatePlaceholder: \"" + this.ID + "\"</b><br>(c) 2003 </p>";
writer.Write(designTimeHTML);
}
else
base.Render(writer);
}
#endregion Render method
}
/// <summary>
/// Specifies the possibilities if controls shall be persisted or not
/// </summary>
public enum HandleDynamicControls
{
/// <summary>
/// DynamicControl shall not be persisted
/// </summary>
DontPersist,
/// <summary>
/// DynamicControl shall be persisted
/// </summary>
Persist,
/// <summary>
/// An Exception shall be thrown
/// </summary>
ThrowException
}
/// <summary>
/// Represents the method that will handle any DynamicControl event.
/// </summary>
[Serializable]
public delegate void DynamicControlEventHandler(object sender, DynamicControlEventArgs
e);
/// <summary>
/// Provides data for the ControlRestored event
/// </summary>
public class DynamicControlEventArgs : EventArgs
{
private Control _dynamicControl;
/// <summary>
/// Gets the referenced Control when the event is raised
/// </summary>
public Control DynamicControl
{
get { return _dynamicControl; }
}
/// <summary>
/// Initializes a new instance of DynamicControlEventArgs class.
/// </summary>
/// <param name="dynamicControl">The control that was just restored.</param>
public DynamicControlEventArgs(Control dynamicControl)
{
_dynamicControl = dynamicControl;
}
}
}
-----------------------------------------------------------
To stop getting this e-mail, or change how often it arrives, go to your E-mail
Settings.
http://groups.msn.com/BDOTNET/_emailsettings.msnw
Need help? If you've forgotten your password, please go to Passport Member Services.
http://groups.msn.com/_passportredir.msnw?ppmprop=help
For other questions or feedback, go to our Contact Us page.
http://groups.msn.com/contact
If you do not want to receive future e-mail from this MSN group, or if you received
this message by mistake, please click the "Remove" link below. On the pre-addressed
e-mail message that opens, simply click "Send". Your e-mail address will be deleted
from this group's mailing list.
mailto:[EMAIL PROTECTED]
