Handling tilde (~) paths in ASCX correctly using ParseControl

Using ParseControl to load ASCX files stored as EmbeddedResource, I found that tilde paths (“~” denoting app root) were not interpreted to mean application root, but were left unchanged in markup attributes.

The solution is to set the AppRelativeTemplateSourceDirectory member variable of the loading control:

Control userControl = page.ParseControl(content);
this.AppRelativeTemplateSourceDirectory =
    userControl.AppRelativeTemplateSourceDirectory;
this.Controls.Add(userControl);