If you are using the .Net Entity Framework and you are passing those Entity Framework objects through controls in your UI (.aspx, .ascx) pages such as a Repeater control (using the ) you will most likely see the following error message:
CS0012: The type ‘System.Data.Objects.DataClasses.EntityObject’ is defined in an assembly that is not referenced. You must add a reference to assembly ‘System.Data.Entity, Version=126.96.36.199, Culture=neutral, PublicKeyToken=b77a5c561934e089’.
You may have added the assembly to your web application’s References but I guess this is not enough. You must also add the reference to your web.config file. You can do this by adding the following line to your ‘compilation/assemblies’ section so it looks like the following: