我意识到这现在已经是一个老话题了，但是我在VS2010中的一个项目中也发生了类似的事情.无法在表单设计器中编辑表单.

I realise this is quite an old thread now, but I just had something similar happen in one of my projects in VS2010. There was no way to edit the Form in the form designer.

最后，在.csproj文件中找到了问题所在.有一个项目组指定要编译的内容.在商品组标签中，对于我的表单，它具有...

In the end tracked it down to a problem in the .csproj file. There is a item group that specifies what is compiled. Within the item group tag, for my form it had ...

<Compile Include="AreaChart.cs" />

它需要...

<Compile Include="AreaChart.cs">
  <SubType>Form</SubType>
</Compile>

缺少SubType XML标记.快速更改项目文件，我可以再次编辑表单.

The SubType XML tag was missing. A quick change to the project file and I could edit the form again.