NameSpace in Embedded package does not create .dll

Recently I want to move URP as an embedded package in order to modify it conveniently . But when I create a test script i found that vscode shows can not find my custom namespace ,but it still can run in Engine and without Error Log in Engine, then I find it does not generate .dll and .csproj of my custom namespace ,i guess this is why vscode can not recognized it. I wonder if there is a way to resolve this problem ? I have regenerate project file for many times.