How to make a custom dependent file in Visual Studio.

From this:
preDependent
To this:
postDependent

Open the .proj file

Find the XML that defines these files

<Compile Include="Models\Context.cs" />
<Compile Include="Models\Client.cs" />
<Compile Include="Models\Image.cs" />
<Compile Include="Models\Office.cs" />
<Compile Include="Models\Policy.cs" />

and add DependentUpon tags

<Compile Include="Models\Context.cs" />
<Compile Include="Models\Client.cs">
  <DependentUpon>Context.cs</DependentUpon>
</Compile>
<Compile Include="Models\Image.cs">
  <DependentUpon>Context.cs</DependentUpon>
</Compile>
<Compile Include="Models\Office.cs">
  <DependentUpon>Context.cs</DependentUpon>
</Compile>
<Compile Include="Models\Policy.cs">
  <DependentUpon>Context.cs</DependentUpon>
</Compile>