FindControl 用于在使用母版页的页面上查找控件

Question

我有这个使用母版页的 aspx：

<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>

但我无法使用此代码访问图像控件：

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

和

Object reference not set to an instance of an object.

发生错误，因为 FindControl("Content1") returns null。请注意，此代码 returns null:

var control = FindControl("i2");

Answer 1

       // 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

Answer 2

您无法访问内容，请参考this question。

也许，您想将 "runat=server" 添加到 div 并访问 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>

然后像这样在代码后面访问控制：

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

FindControl 用于在使用母版页的页面上查找控件

FindControl for finding control on page that uses master page

c#

asp.net

master-pages

findcontrol