A further note on Dmitry's 2017 answer. I opened up
C:\Program Files (x86)\Microsoft Visual
Studio\2017\Community\MSBuild\Microsoft\VisualStudio\Managed\
Microsoft.CSharp.DesignTime.targets
and went to the <ProjectCapability> element. I already had this:
<ProjectCapability Include="
CSharp;
Managed;
ClassDesigner**;**" />
with ClassDesigner already there, and yet I was still unable to drag items to my hack-made Diagram.cd using the XML editing method Dmitry mentioned (
Manually create text file, say MyClasses.cd with following content:
<?xml version="1.0" encoding="utf-8"?> <ClassDiagram MajorVersion="1"
> MinorVersion="1">
> <Font Name="Segoe UI" Size="9" /> </ClassDiagram>
). But when I took off the semicolon off 'ClassDesigner' in that element then reopened Visual Studio, voila, I was able to drag classes from my Solution Explorer to my Diagram.cd window.
So in conclusion, this element in Microsoft.CSharp.DesignTime.targets worked:
<ProjectCapability Include="
CSharp;
Managed;
ClassDesigner" />
I am using VS 2019, version 16.1.5.