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IPostBackDataHandler not working properly with DataGrid

 
 
buzlite@sympatico.ca
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      08-11-2006
Hello All,

I am having some difficulties with a user control implementing
IPostBackDataHandler when it is placed inside a datagrid.

I have created a user control (MyUserControl.ascx) containing 1 TextBox
that implements the IPostBackDataHandler.
I have also created a form (WebForm1.aspx) that contains 1 datagrid of
which the datagrid contains the above user control as specified in its
template.

The purpose is to dynamically create one MyUserControl for each item in
the datasource for display and editing.

When the program is run and text is entered into MyUserControl's
textbox, the LoadPostData() of MyUserControl.ascx is called as
expected. But even though LoadPostData() returns true the
corresponding RaisePostDataChangedEvent() is not called.


Note: if I were to simply include the MyUserControl.ascx in
WebForm1.aspx, then both LoadPostData() and RaisePostDataChangedEvent()
of MyUserControl.ascx are called as expected.

Would someone give me some insight as to why this is not working ? Am
I missing a step somewhere ?


Attached is the bare essential code snippets to reproduce the problem.


MyUserControl.ascx
-----------------------------------------------------
<%@ Control Language="c#" AutoEventWireup="false"
Codebehind="MyUserControl.ascx.cs" Inherits="test.MyUserControl"
TargetSchema="http://schemas.microsoft.com/intellisense/ie5"%>
<asp:TextBox id="TextBox1" runat="server"></asp:TextBox>


MyUserControl.ascx.cs
-----------------------------------------------------
public class MyUserControl : System.Web.UI.UserControl,
IPostBackDataHandler, INamingContainer
{
protected System.Web.UI.WebControls.TextBox TextBox1;


#region Web Form Designer generated code
override protected void OnInit(EventArgs e)
{
//
// CODEGEN: This call is required by the ASP.NET Web Form Designer.
//
InitializeComponent();
base.OnInit(e);

if (Page != null)
{
Page.RegisterRequiresPostBack(this);
}
}

/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
this.Load += new System.EventHandler(this.Page_Load);

}
#endregion


public virtual bool LoadPostData(string postDataKey,
System.Collections.Specialized.NameValueCollection postCollection)
{
return true;
}

public virtual void RaisePostDataChangedEvent()
{
}

private void Page_Load(object sender, System.EventArgs e)
{
}
}



WebForm1.aspx
------------------------------------------------------
<%@ Register TagPrefix="f4c" TagName="MyUserControl"
Src="MyUserControl.ascx" %>
<%@ Page language="c#" Codebehind="WebForm1.aspx.cs"
AutoEventWireup="false" Inherits="test.WebForm1" %>
....
<form id="Form1" method="post" runat="server">
<asp:datagrid id="dgListing" runat="server"
AutoGenerateColumns="False">
<Columns>
<asp:TemplateColumn>
<ItemTemplate>
<f4c:MyUserControl id="MyUserControl1"
runat="server"></f4c:MyUserControl>
</ItemTemplate>
</asp:TemplateColumn>
</Columns>
</asp:datagrid>
<asp:Button id="Button1" runat="server" Text="Button"></asp:Button>
</form>


WebForm1.aspx.cs
------------------------------------------------------
public class WebForm1 : System.Web.UI.Page
{

....
private void Page_Load(object sender, System.EventArgs e)
{
//setup handlers
this.Button1.Click += new System.EventHandler(this.Button1_Click);

//setup datagrid
dgListing.DataSource = this.CreateDataSource();
dgListing.DataBind();
}

private void Button1_Click(object sender, System.EventArgs e)
{
}

ICollection CreateDataSource()
{
DataTable dt = new DataTable();
DataRow dr;

dt.Columns.Add(new DataColumn("SomeColumn", typeof(Int32)));

for (int i = 0; i < 2; i++)
{
dr = dt.NewRow();
dr[0] = i;
dt.Rows.Add(dr);
}

DataView dv = new DataView(dt);
return dv;
}
}

 
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