Client web part / App Part showing the blank iframe on page

Hello all - While creating first hello client web part many times people face this issue that there cleint web part show blank window after adding on page.

For showing content on page need to allow framing on page as client web parts loan in iFrame.

<WebPartPages:AllowFraming runat="server" />

Check for above line of code on client web part file. If not preset add it there.