Getting text entered in textbox of other applications using C#

Question

I want to get the text which is in textbox of other application. It may be a textbox of gtalk client or a soap UI screen.

Based on my research most of the forums suggested winapi is the concept that I've to use to achieve this. I didn't get any good examples to implement this.

Answer 1

Here is an example of how to grab all the text from a window by it's window title.

Please see the comments for an explanation on how this works.

public class GetWindowTextExample
{
    // Example usage.
    public static void Main()
    {
        var allText = GetAllTextFromWindowByTitle("Untitled - Notepad");
        Console.WriteLine(allText);
        Console.ReadLine();
    }

    // Delegate we use to call methods when enumerating child windows.
    private delegate bool EnumWindowProc(IntPtr hWnd, IntPtr parameter);

    [DllImport("user32")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool EnumChildWindows(IntPtr window, EnumWindowProc callback, IntPtr i);

    [DllImport("user32.dll", EntryPoint = "FindWindow", SetLastError = true)]
    private static extern IntPtr FindWindowByCaption(IntPtr zeroOnly, string lpWindowName);

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

    // Callback method used to collect a list of child windows we need to capture text from.
    private static bool EnumChildWindowsCallback(IntPtr handle, IntPtr pointer)
    {
        // Creates a managed GCHandle object from the pointer representing a handle to the list created in GetChildWindows.
        var gcHandle = GCHandle.FromIntPtr(pointer);

        // Casts the handle back back to a List<IntPtr>
        var list = gcHandle.Target as List<IntPtr>;

        if (list == null)
        {
            throw new InvalidCastException("GCHandle Target could not be cast as List<IntPtr>");
        }

        // Adds the handle to the list.
        list.Add(handle);

        return true;
    }

    // Returns an IEnumerable<IntPtr> containing the handles of all child windows of the parent window.
    private static IEnumerable<IntPtr> GetChildWindows(IntPtr parent)
    {
        // Create list to store child window handles.
        var result = new List<IntPtr>();

        // Allocate list handle to pass to EnumChildWindows.
        var listHandle = GCHandle.Alloc(result);

        try
        {
            // Enumerates though all the child windows of the parent represented by IntPtr parent, executing EnumChildWindowsCallback for each. 
            EnumChildWindows(parent, EnumChildWindowsCallback, GCHandle.ToIntPtr(listHandle));
        }
        finally
        {
            // Free the list handle.
            if (listHandle.IsAllocated)
                listHandle.Free();
        }

        // Return the list of child window handles.
        return result;
    }

    // Gets text text from a control by it's handle.
    private static string GetText(IntPtr handle)
    {
        const uint WM_GETTEXTLENGTH = 0x000E;
        const uint WM_GETTEXT = 0x000D;

        // Gets the text length.
        var length = (int)SendMessage(handle, WM_GETTEXTLENGTH, IntPtr.Zero, null);

        // Init the string builder to hold the text.
        var sb = new StringBuilder(length + 1);

        // Writes the text from the handle into the StringBuilder
        SendMessage(handle, WM_GETTEXT, (IntPtr)sb.Capacity, sb);

        // Return the text as a string.
        return sb.ToString();
    }

    // Wraps everything together. Will accept a window title and return all text in the window that matches that window title.
    private static string GetAllTextFromWindowByTitle(string windowTitle)
    {
        var sb = new StringBuilder();

        try
        {
            // Find the main window's handle by the title.
            var windowHWnd = FindWindowByCaption(IntPtr.Zero, windowTitle);

            // Loop though the child windows, and execute the EnumChildWindowsCallback method
            var childWindows = GetChildWindows(windowHWnd);

            // For each child handle, run GetText
            foreach (var childWindowText in childWindows.Select(GetText))
            {
                // Append the text to the string builder.
                sb.Append(childWindowText);
            }

            // Return the windows full text.
            return sb.ToString();
        }
        catch (Exception e)
        {
            Console.Write(e.Message);
        }

        return string.Empty;
    }
}