How to run multiple c# programs in one project in Visual Studio

I'm new to programming and visual studio. I'm just starting with c# in VS. I want to run multiple programs one by one, I wrote two programs and when I try to run them I think the entire project is running but I can see the output of only the first program, not the others. When I try to put one file as startup it's not allowing me to:

Thanks in advance.

I think there is a problem with your thinking at the beginning. For example, if you want to run two different code blocks to achieve different operations, you should not expect the main method to help you, because usually a project can only have one entry. Maybe because you are a novice, you may not know that there is a basic operation in C# that writes an independent operation as a method. If this is not what you want, please let me know. For example, the code you provided can be written like this:

namespace testProject
{
     class prj2
     {
         public void test()
         {
             Console. WriteLine("Hello");
         }
     }
}

Then add the above method in the program, the operation is as follows:

using testProject;
 
Console. WriteLine("Hello, World!");
 
prj2 prj2= new prj2();
prj2.test();

In this way, two paragraphs can be output at the same time:

For details, you can refer to: https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/methods

You must create two different projects to be able to run both at same time in Visual Studio. Once you have created two projects in the same solution take a look at the documentation here