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Loading ImageButtons Dynamically using FindControl

Posted By:      Posted Date: September 22, 2010    Points: 0   Category :ASP.Net

I have a table where each cell contains an ImageButton, with an iterative ID:

	<asp:TableCell ID="zm_1">
		<asp:ImageButton ID="zmi_1"  runat="server" Height="15px" Width="15px" />
	<asp:TableCell ID="zm_2">
		<asp:ImageButton ID="zmi_2"  runat="server" Height="15px" Width="15px" />
	<asp:TableCell ID="zm_3">
		<asp:ImageButton ID="zmi_3"  runat="server" Height="15px" Width="15px" />

I am then trying to assign a URL to each imagebutton dynamically in a separate code file

ContentPlaceHolder MainContent = Page.Master.FindControl("MainContent") as ContentPlaceHolder;
ImageButton button = new ImageButton();
for (int i=1;i <=3; i++)
        button = MainContent.FindControl("zmi_" + i.ToString()) as ImageButton;
        button.ImageUrl = Server.MapPath("~/img/some_image.jpg");

Everything compiles, but when I run this I throw a Null Reference Exception:  {"Object reference not set to an instance of an object."}


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