The type 'Microsoft.SharePoint.WebPartPages.WebPartPage' exists in both

Question

I have a problem here:

An error occurred during the compilation of the requested file, or one of its dependencies. The type 'Microsoft.SharePoint.WebPartPages.WebPartPage' exists in both 'c:\Windows\Microsoft.NET\assembly\GAC_MSIL\MyProject\v4.0_1.0.0.0__4829610975c6feae\MyProject.dll' and 'c:\Windows\Microsoft.NET\assembly\GAC_MSIL\Microsoft.SharePoint\v4.0_15.0.0.0__71e9bce111e9429c\Microsoft.SharePoint.dll'

When I enter/create/view list item of particular content type I receive this error. I'm new to SharePoint and this error sounds for me like nonsense. When I simply save my master page (so it's no longer based on my site definition) it fixes my problem. I have none of my code in my master page.

when I return it to site definition, error gets back.

how its connected to my master page and site definition? how to fix this? because all I have for now is workaround... please help, I searched everywhere.

Answer 1

well seems I found a solution. I messed up with namespaces and inheritance when I was creating custom pages for my content type.

I just added something like that:

<%@ Page language="C#" MasterPageFile="~masterurl/default.master"    Inherits="Microsoft.SharePoint.WebPartPages.WebPartPage,Microsoft.SharePoint,Version=15.0.0.0,Culture=neutral,PublicKeyToken=71e9bce111e9429c" meta:webpartpageexpansion="full" meta:progid="SharePoint.WebPartPage.Document"  %>
<%@ Register Tagprefix="SharePoint" Namespace="Microsoft.SharePoint.WebControls" Assembly="Microsoft.SharePoint, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %> <%@ Register Tagprefix="Utilities" Namespace="Microsoft.SharePoint.Utilities" Assembly="Microsoft.SharePoint, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %> <%@ Import Namespace="Microsoft.SharePoint" %> <%@ Assembly Name="Microsoft.Web.CommandUI, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %> <%@ Register Tagprefix="WebPartPages" Namespace="Microsoft.SharePoint.WebPartPages" Assembly="Microsoft.SharePoint, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>

and it worked just fine.