Question

I am trying to import the GetWindowText in a VB.NET application.

So based on other sites you just have to import the interopt service and add a DLLImport statement similar to C#. But somehow it is not recognizing the statement and getting a BC30001 (Statement is not valid in a namespace) compile error.

Here is the code I used.

Imports System.Runtime.InteropServices

<DllImport("user32", CharSet:=CharSet.Auto, SetLastError:=True)> _
Public Shared Function GetWindowText(ByVal hWnd As IntPtr, <Out(), MarshalAs(UnmanagedType.LPTStr)> ByVal lpString As StringBuilder, ByVal nMaxCount As Integer) As Integer
End Function

What assembly do I need to import to make this work? Any ideas?

Answer 1

The problem has nothing to do with importing assemblies. You simply cannot define free functions in a namespace in VB.NET.

You have to place them in either a Module (basically a static class) or a Class.

It’s recommended you place native Win32 functions in a class named NativeMethods anyway, so rewrite your code to look like this:

Imports System.Runtime.InteropServices

Friend Class NativeMethods

    <DllImport("user32", CharSet:=CharSet.Auto, SetLastError:=True)> _
    Public Shared Function GetWindowText(ByVal hWnd As IntPtr,
        <Out(), MarshalAs(UnmanagedType.LPTStr)> ByVal lpString As StringBuilder,
        ByVal nMaxCount As Integer) As Integer
    End Function

End Class