In your master page's code behind replace the protected keyword on the event handler to public.
public void LinkButton1_Click(object sender, EventArgs e)
{
}
IN your content page use the Master Type Directive
<![CDATA[<%@ MasterType VirtualPath="~/masters/SourcePage.master"" %>]]>
In the code behind for the content page call the Master event handler as follows
protected void ImageButton1_Click(object sender, ImageClickEventArgs e)
{
this.Master.LinkButton1_Click(sender, e);
}
See some good links for this point. And go through this you will bit clear more
interacting-with-the-content-page-from-the-master-page-cs[
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