For page validation Google chrome error -" ReferenceError: Page_ClientValidate is not defined "

Hello
In my web project i am using file upload control .With the help of this i have to change the image.
So i need to validate that if user has slected image in file upload control then and then only change existing image.
 for this i used following method in javascript
function Picturevalidation() {
    try
    {
       return Page_ClientValidate('Pic');
    }

and calling this method OnClientClick of button as-
<asp:Button ID="cmdChangePicture" runat="server" CssClass="popup_buttons"
onclick="cmdChangePicture_Click" Text="Change Picture" OnClientClick="return Picturevalidation();"
meta:resourcekey="cmdChangePictureResource1"/> ...