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GetWindowText (user32)
 
.
Summary
Copies the text of the specified window's title bar (if it has one) into a buffer. If the specified window is a control, the text of the control is copied. However, GetWindowText cannot retrieve the text of a control in another application, If the target window is owned by the current process, GetWindowText causes a WM_GETTEXT message to be sent to the specified window or control.
Remarks
If the target window is owned by another process and has a caption, GetWindowText retrieves the window caption text. If the window does not have a caption, the return value is a null string. This behavior is by design. It allows applications to call GetWindowText without becoming unresponsive if the process that owns the target window is not responding. However, if the target window is not responding and it belongs to the calling application, GetWindowText will cause the calling application to become unresponsive.

To retrieve the text of a control in another process, send a WM_GETTEXT message directly instead of calling GetWindowText.

To retrieve the text of a possibly unresponsive control in the same process, use SendMessageTimeout with a WM_GETTEXT message instead.

C# Signature:

/// <summary>
///     Copies the text of the specified window's title bar (if it has one) into a buffer. If the specified window is a
///     control, the text of the control is copied. However, GetWindowText cannot retrieve the text of a control in another
///     application.
///     <para>
///     Go to https://msdn.microsoft.com/en-us/library/windows/desktop/ms633520%28v=vs.85%29.aspx  for more
///     information
///     </para>
/// </summary>
/// <param name="hWnd">
///     C++ ( hWnd [in]. Type: HWND )<br />A <see cref="IntPtr" /> handle to the window or control containing the text.
/// </param>
/// <param name="lpString">
///     C++ ( lpString [out]. Type: LPTSTR )<br />The <see cref="StringBuilder" /> buffer that will receive the text. If
///     the string is as long or longer than the buffer, the string is truncated and terminated with a null character.
/// </param>
/// <param name="nMaxCount">
///     C++ ( nMaxCount [in]. Type: int )<br /> Should be equivalent to
///     <see cref="StringBuilder.Length" /> after call returns. The <see cref="int" /> maximum number of characters to copy
///     to the buffer, including the null character. If the text exceeds this limit, it is truncated.
/// </param>
/// <returns>
///     If the function succeeds, the return value is the length, in characters, of the copied string, not including
///     the terminating null character. If the window has no title bar or text, if the title bar is empty, or if the window
///     or control handle is invalid, the return value is zero. To get extended error information, call GetLastError.<br />
///     This function cannot retrieve the text of an edit control in another application.
/// </returns>
/// <remarks>
///     If the target window is owned by the current process, GetWindowText causes a WM_GETTEXT message to be sent to the
///     specified window or control. If the target window is owned by another process and has a caption, GetWindowText
///     retrieves the window caption text. If the window does not have a caption, the return value is a null string. This
///     behavior is by design. It allows applications to call GetWindowText without becoming unresponsive if the process
///     that owns the target window is not responding. However, if the target window is not responding and it belongs to
///     the calling application, GetWindowText will cause the calling application to become unresponsive. To retrieve the
///     text of a control in another process, send a WM_GETTEXT message directly instead of calling GetWindowText.<br />For
///     an example go to
///     <see cref="!:https://msdn.microsoft.com/en-us/library/windows/desktop/ms644928%28v=vs.85%29.aspx#sending">
///     Sending a
///     Message.
///     </see>
/// </remarks>
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
static extern int GetWindowText(IntPtr hWnd, StringBuilder lpString, int nMaxCount);

VB.NET Signature:

<DllImport("user32.dll", EntryPoint:="GetWindowText")>
Public Function GetWindowText(ByVal hwnd As Integer, ByVal lpString As System.Text.StringBuilder, ByVal cch As Integer) As Integer
End Function

Oxygene.NET Signature:

[DllImport("user32.dll", CharSet := CharSet.Auto, SetLastError := true)]
class method GetWindowText(hWnd: IntPtr; lpString: StringBuilder; nMaxCount: Int32): Int32; external;

VB Signature:

Public Declare Function GetWindowText Lib "user32.dll" Alias "GetWindowTextA" _
        (ByVal hWnd As Long, _
         ByVal prmstrString As String, _
         ByVal nMaxCount As Long) As Long

User-Defined Types:

None.

Notes:

See also GetWindowTextLength

Tips & Tricks:

Please add some!

Sample Code:

public static string GetText(IntPtr hWnd)
{
    // Allocate correct string length first
    int length       = GetWindowTextLength(hWnd);
    StringBuilder sb = new StringBuilder(length + 1);
    GetWindowText(hWnd, sb, sb.Capacity);
    return sb.ToString();
}

But, if you need to get text from a control in another process, GetWindowText() won't work. Use WM_GETTEXT instead.

Sample Code:

[DllImport("user32.dll", CharSet = CharSet.Auto)]
static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, [Out] StringBuilder lParam);

public static string GetWindowTextRaw(IntPtr hwnd)
{
    // Allocate correct string length first
    int length = (int)SendMessage(hwnd, WM_GETTEXTLENGTH, IntPtr.Zero, IntPtr.Zero);
    StringBuilder sb = new StringBuilder(length + 1);
    SendMessage(hwnd, WM_GETTEXT, (IntPtr)sb.Capacity, sb);
    return sb.ToString();
}

vb.net sample

Public Function GetText(ByVal hWnd As IntPtr) As String
    Dim length As Integer
    If hWnd.ToInt32 = 0 Then
        Return Nothing
    End If
    length = GetWindowTextLength(hWnd)
    If length = 0 Then
        Return Nothing
    End If
    Dim sb As New System.Text.StringBuilder("", length)

    GetWindowText(hWnd, sb, sb.Capacity + 1)
    Return sb.ToString()
End Function

Alternative Managed API:

The ManagedWindowsApi project (http://mwinapi.sourceforge.net) provides a

class ManagedWinapi.SystemWindow that has a Title property.

http://css.lgv.lt

Documentation

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