FindControl for finding control on page that uses master page

Question

I have this aspx that uses a master page:

<asp:Content ID="Content1" ContentPlaceHolderID="content" runat="server">
   <div class="mlists">
       <a href="?"><img id="i1" src="../img/1.png" runat="server" alt="1"/></a>
       <a href="?"><img id="i2" src="../img/2.png" runat="server" alt="2"/></a> 
       <a href="?"><img id="i3" src="../img/3.png" runat="server" alt="3"/></a> 

   </div>
</asp:Content>

but I can't access to image controls using this code:

var control = FindControl("Content1").FindControl("i2");
((HtmlImage)control).Src = "../img/x.png";

and

Object reference not set to an instance of an object.

error occurs, since FindControl("Content1") returns null. note that also this code returns null:

var control = FindControl("i2");

then just call it as `i2`. the code-behind will have it as of type `System.Web.UI.HtmlControls.HtmlImage` — naveen, May 04 '15 at 08:02
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/76862/discussion-between-naveen-and-majidgeek). — naveen, May 04 '15 at 08:08
[Perhaps this link will help](https://msdn.microsoft.com/en-us/library/y81z8326(v=vs.140).aspx?cs-save-lang=1&cs-lang=csharp#code-snippet-2) — Zohar Peled, May 04 '15 at 08:33

score 0 · Answer 1 · answered May 04 '15 at 11:26

       // Get a reference to the master page
        MasterPage ctl00 = FindControl("ctl00") as MasterPage;

        // Get a reference to the ContentPlaceHolder
        ContentPlaceHolder mainContent = ctl00.FindControl("MainContent") as ContentPlaceHolder;

           // Get a reference to the Repeater
       Repeater repeater = mainContent.FindControl("Repeater1") as Repeater;

  This is how i get to a repeater control in a working application.
Follow this pattern you can get anything in your master page and even content page

score 0 · Accepted Answer · edited May 23 '17 at 11:43

You can't access content, please refer to this question.

Perhaps, you wanted to add "runat=server" to div and access ImageControls.

<asp:Content ID="Content1" runat="server" ContentPlaceHolderID="content">
    <div class="mlists" runat="server" id="div">
       <a href="?"><img id="i1" src="../img/1.png" runat="server" alt="1"/></a>
       <a href="?"><img id="i2" src="../img/2.png" runat="server" alt="2"/></a> 
       <a href="?"><img id="i3" src="../img/3.png" runat="server" alt="3"/></a> 

   </div>
</asp:Content>

Then access controls in code behind like this:

var control = div.FindControl("i2");
((HtmlImage)control).Src = "../img/x.png";

FindControl for finding control on page that uses master page

2 Answers2