C# Signature:

[DllImport("user32.dll", SetLastError = true, CharSet= CharSet.Auto)]
public static extern int MessageBox(IntPtr hWnd, String text, String caption, uint type);

VB.Net Signature:

Please Add Some!

VB Signature:

Private Declare Function MessageBox Lib "user32.dll" Alias "MessageBoxA" (ByVal hWnd As Long, ByVal lpText As String, ByVal lpCaption As String, ByVal uType As Long) As Long

Alternative Managed API:

System.Windows.Forms.MessageBox (WinForms)

System.Windows.MessageBox (WPF)

Notes:

https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-messagebox