Get the title of the active window

dllimport, user32, vb.net, winapi, winforms

Solution

<DllImport("USER32.DLL", EntryPoint:="GetWindowText", SetLastError:=True,
    CharSet:=CharSet.Unicode, ExactSpelling:=True,

You insisted on ExactSpelling. Which is the problem, there are two versions of GetWindowText exported by user32.dll. GetWindowTextA and GetWindowTextW. The A version uses an ansi string, a legacy string format with 8-bit characters encoded in the default code page that was last used in Windows ME. The W version uses a Unicode string, encoded in utf-16, the native Windows string type. The pinvoke marshaller will try either of them, based on the CharSet but you stopped it from doing so by using ExactSpelling := True. So it cannot find GetWindowText, it doesn't exist.

Either use EntryPoint := "GetWindowTextW" or drop ExactSpelling.

Problem

I have declared the following WinAPI calls ``` <DllImport("USER32.DLL", EntryPoint:="GetActiveWindow", SetLastError:=True, CharSet:=CharSet.Unicode, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> Public Shared Function GetActiveWindowHandle() As System.IntPtr End Function <DllImport("USER32.DLL", EntryPoint:="GetWindowText", SetLastError:=True, CharSet:=CharSet.Unicode, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> Public Shared Function GetActiveWindowText(ByVal hWnd As System.IntPtr, _ ByVal lpString As System.Text.StringBuilder, _ ByVal cch As Integer) As Integer End Function ``` Then, I call this subroutine to get the text in the active window's title bar ``` Public Sub Test() Dim caption As New System.Text.StringBuilder(256) Dim hWnd As IntPtr = GetActiveWindowHandle() GetActiveWindowText(hWnd, caption, caption.Capacity) MsgBox(caption.ToString) End Sub ``` Finally, I get the following error Unable to find an entry point named 'GetWindowText' in DLL 'USER32.DLL' How can I fix this issue?

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