Get window hwnd if owner hwnd, class name and size of the window are known

Question

I need some specific help. I know the class name, the owner hwnd and the size of a window. How do I get its hwnd? Or, at least, get a list of all the windows meeting those conditions.

Thanks in advance!

Vali

Answer 1

You can try using this code. It will give you an IntPtr (the window handle) of each top-level window with a particular class name:

/// <summary>
/// Returns a sequence of window handles (IntPtrs) for all top-level windows
/// matching the specfied window class name.
/// </summary>
/// <param name="className">The windows class name to match (not to be confused with a C# class name!)</param>
/// <returns>A non-null sequence of window handles. This will be an empty sequence if no windows match the class name.</returns>

public static IEnumerable<IntPtr> WindowsMatchingClassName(string className)
{
    if (string.IsNullOrWhiteSpace(className))
    {
        throw new ArgumentOutOfRangeException("className", className, "className can't be null or blank.");
    }

    return WindowsByClassFinder.WindowsMatching(className);
}

/// <summary>Finds windows matching a particular window class name.</summary>

private class WindowsByClassFinder
{
    /// <summary>Find the windows matching the specified class name.</summary>

    public static IEnumerable<IntPtr> WindowsMatching(string className)
    {
        return new WindowsByClassFinder(className)._result;
    }

    private WindowsByClassFinder(string className)
    {
        _className = className;
        EnumWindows(callback, IntPtr.Zero);
    }

    private bool callback(IntPtr hWnd, IntPtr lparam)
    {
        if (GetClassName(hWnd, _apiResult, _apiResult.Capacity) != 0)
        {
            if (string.CompareOrdinal(_apiResult.ToString(), _className) == 0)
            {
                _result.Add(hWnd);
            }
        }

        return true; // Keep enumerating.
    }

    [SuppressMessage("Microsoft.Security", "CA2118:ReviewSuppressUnmanagedCodeSecurityUsage"), SuppressUnmanagedCodeSecurity]
    [DllImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private extern static bool EnumWindows(EnumWindowsDelegate lpEnumFunc, IntPtr lparam);

    [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
    private static extern int GetClassName(IntPtr hWnd, StringBuilder lpClassName, int nMaxCount);

    private delegate bool EnumWindowsDelegate(IntPtr hWnd, IntPtr lparam);

    private readonly string _className;
    private readonly List<IntPtr> _result = new List<IntPtr>();
    private readonly StringBuilder _apiResult = new StringBuilder(1024);
}