它们在DLL级别上是相同的，因此只需在c#项目中引用vb.net.

They are the same at the DLL level so just reference vb.net in your c# project.

您不能将两个应用程序直接添加到一起.如果要添加一些代码或函数，则可以创建该cade的dll(动态链接库)文件.创建dll之后，您可以将该dll的引用添加到C#项目

You can not Add both application together as it is.If you want to add some code or functions then you can make dll(Dynamic link library) file of that cade.after creating dll you can add the reference of that dll into the C# Project

Steps : Right Click on Project In Solution Explorer->Add Reference.

但是首先，您必须学习如何制作类库即(DLL).
如果您想大量引用代码，这很好.
如果您希望使用少量代码，请尝试使用转换工具将该代码转换为Vb.Net.

But for that first of all you have to learn how to make Class Library i.e.(DLL).
This is good when you want to refer large quantity if code.
If you want small lines of code then try to convert that code into Vb.Net using Conversion tools.