Environment

VB.net
.NET Core 3.1
Windows 10

Aim

Call a console window from forms, using AllocConsole() function. Especially, the case of calling a console application (project) from a form application (project) in a same solution of Visual Studio.

References

C#(Windows Formアプリケーション)でコンソールの表示、非表示、出力方法(Console.WriteLine()) - Qiita

Code

Private Declare Function AllocConsole Lib "kernel32" () As Integer
Private Declare Function FreeConsole Lib "kernel32" () As Integer

Sub SomeName()
    AllocConsole()
    Console.SetOut(New StreamWriter(Console.OpenStandardOutput()) With {.AutoFlush = True})

    'Set the size of the console window into an appropriate size.
    Console.SetWindowSize(40, 20)
    Console.SetBufferSize(80, 80)


    Try
        '(...)
    Finally
        FreeConsole()
    End Try


End Sub

Note

AllocConsole() function allocates a console window to the process.
Console.SetOut(...) defines the output stream of the console window. Without it, when the procedure Sub SomeName is called twice or more, functions like Console.Writeline(...) would throw exceptions even though after AllocConsole().
- In some cases, specifying encoding may be needed, like
  Dim enc As Text.Encoding = ...
  Console.SetOut(New StreamWriter(Console.OpenStandardOutput(), enc) With {.AutoFlush = True})
FreeConsole() closes the console window.