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Find button control in GridView within an UpdatePanel

I am trying to grab the value of the txtPostRely textbox control but I get a null exception. Here is the code.

<asp:UpdatePanel ID="panelPost" runat="server">
<ContentTemplate>
<asp:GridView ID="grdPosts" runat="server"
AutoGenerateColumns="False"
Width="100%"
AllowPaging="True"
PageSize="5"
DataSourceID="sqldsPosts"
DataKeyNames="PostID">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<h2><%# Eval("Title") %></h2>

<cc1:CollapsiblePanelExtender ID="collapsePostView" runat="server"
TargetControlID="panelPostViewContent"
ExpandControlID="panelPostViewTitle"
CollapseControlID="panelPostViewTitle"
Collapsed="true"
ExpandDirection="Vertical"
TextLabelID="Label1"
ExpandedText="Hide Form"
CollapsedText="Reply"
CollapsedImage="~/App_Themes/images/button-go.gif"
ExpandedImage="~/App_Themes/images/button-go.gif"
/>

<asp:Panel ID="panelPostViewTitle" runat="server">
<asp:Label ID="Label1" runat="server">Reply</asp:Label>
</asp:Panel>
<asp:Panel ID="panelPostViewContent" runat="server">
<%# Eval("Message") %>

Reply:
<br /><asp:TextBox ID="txtPostReply" runat="server" Rows="5" Columns="40"></asp:TextBox>
<br /><asp:LinkButton ID="btnReplySubmit" runat="server"
Text="Submit"
OnCommand="grdPosts_AddReply"
CommandName="AddReply"
CommandArgument='<%# Eval("PostID") %>'
/>
</asp:Panel>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>

<asp:SqlDataSource ID="sqldsPosts" runat="server"
ConnectionString="<%$ ConnectionStrings:SQL %>"
SelectCommand="SELECT * FROM [ForumPosts] ORDER BY [PostID] DESC">
</asp:SqlDataSource>
</ContentTemplate>
</asp:UpdatePanel>

protected void grdPosts_AddReply(object sender, System.Web.UI.WebControls.CommandEventArgs e)
{
	int? postID = Convert.ToInt32(e.CommandArgument.ToString());
 
	// Find control
	TextBox txtPostReply = (TextBox)panelPostViewContent.FindControl("txtPostReply");
}

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tristamane

ASKER

Here is my fix.

Place the PostID and row index in the CommandArgument.

<asp:LinkButton ID="btnReplySubmit" runat="server"
Text="Submit"
OnCommand="grdPosts_AddReply"
CommandName="AddReply"
CommandArgument='<%# Eval("PostID") + "," + string.Format("{0}", ((GridViewRow)Container).RowIndex + 1) %>'
/>

Split the argument and find the control.

// Split the command args
string[] commandArguments = e.CommandArgument.ToString().Split(',');

// Set the post, index and new id
int? postID = Convert.ToInt32(commandArguments[0]);
int index = Convert.ToInt32(commandArguments[1]);

// Find control
TextBox txtPostReply = (TextBox)grdPosts.Rows[index - 1].Cells[0].FindControl("txtPostReply");