如何修复Entity Framework 4.1模型模板中丢失的类型/命名空间错误？

.edmx

<#@ template language=\"C#\" debug=\"false\" hostspecific=\"true\"#>
<#@ include file=\"EF.Utility.CS.ttinclude\"#>
<#@ output extension=\".cs\"#>

error CS0234: The type or namespace name \'Design\' does not exist in the namespace \'System.Data.Entity\'...
error CS0246: The type or namespace name \'EnvDTE\' could not be found (are you missing a using directive...
error CS0234: The type or namespace name \'VisualStudio\' does not exist in the namespace \'Microsoft\'...

<Compile Include=\"SomeModel.tt\">
  <Generator>TextTemplatingFileGenerator</Generator>
  <LastGenOutput>SomeModel.cs</LastGenOutput>
</Compile>

<None Include=\"SomeModel.tt\">
  <Generator>TextTemplatingFileGenerator</Generator>
  <LastGenOutput>SomeModel.cs</LastGenOutput>
</None>

.tt

.tt

<#@ template language=\"C#\" debug=\"false\" hostspecific=\"true\"#>
<#@ assembly name=\"System.Data.Entity\" #>
<#@ assembly name=\"System.Data.Entity.Design\" #>
...