Get selected text using SendMessage

Question

Lets say i have the handler of the window contains the selected text ..

And all i need is to fetch the selected text from this window.

I know we can do this using SendMessage() API and EM_GETSEL constant , but i am really confused how to do that !

Answer 1

WM_GETTEXT message will help you out -

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace TextFocusedns 
{
    public partial class TextFocusedFrm : Form
    {
        #region APIs

        [DllImport("user32.dll")]
        public static extern bool GetCursorPos(out Point pt);

        [DllImport("user32.dll", EntryPoint = "WindowFromPoint", CharSet = CharSet.Auto, ExactSpelling = true)]
        public static extern IntPtr WindowFromPoint(Point pt);

        [DllImport("user32.dll", EntryPoint = "SendMessageW")]
        public static extern int SendMessageW([InAttribute] System.IntPtr hWnd, int Msg, int wParam, IntPtr lParam);
        public const int WM_GETTEXT = 13;

        [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
        internal static extern IntPtr GetForegroundWindow();

        [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
        internal static extern IntPtr GetFocus();
    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    internal static extern int GetWindowThreadProcessId(int handle, out int processId);

    [DllImport("user32", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
    internal static extern int AttachThreadInput(int idAttach, int idAttachTo, bool fAttach);
    [DllImport("kernel32.dll")]
    internal static extern int GetCurrentThreadId();

    [DllImport("user32", CharSet = CharSet.Auto, SetLastError = true)]
    internal static extern int GetWindowText(IntPtr hWnd, [Out, MarshalAs(UnmanagedType.LPTStr)] StringBuilder lpString, int nMaxCount);

    #endregion

    private System.Windows.Forms.Timer timer = new System.Windows.Forms.Timer() { Interval = 100, Enabled = true };

    public TextFocusedFrm()
    {
        InitializeComponent();
    }

    private void TextFocusedFrm_Load(object sender, EventArgs e)
    {
        timer.Tick += new EventHandler(timer_Tick);
        timer.Start();
    }

    void timer_Tick(object sender, EventArgs e)
    {
        try
        {
            MultiLineTextBox.Text = GetTextFromFocusedControl();
        }
        catch (Exception exp)
        {
            MultiLineTextBox.Text += exp.Message;
        }
    }

    //Get the text of the focused control
    private string GetTextFromFocusedControl()
    {
        try
        {
            int activeWinPtr = GetForegroundWindow().ToInt32();
            int activeThreadId = 0, processId;
            activeThreadId = GetWindowThreadProcessId(activeWinPtr, out processId);
            int currentThreadId = GetCurrentThreadId();
            if (activeThreadId != currentThreadId)
                AttachThreadInput(activeThreadId, currentThreadId, true);
            IntPtr activeCtrlId = GetFocus();

            return GetText(activeCtrlId);
        }
        catch (Exception exp)
        {
            return exp.Message;
        }
    }

    //Get the text of the control at the mouse position
    private string GetTextFromControlAtMousePosition()
    {
        try
        {
            Point p;
            if (GetCursorPos(out p))
            {
                IntPtr ptr = WindowFromPoint(p);
                if (ptr != IntPtr.Zero)
                {
                    return GetText(ptr);
                }
            }
            return "";
        }
        catch (Exception exp)
        {
            return exp.Message;
        }
    }

    //Get the text of a control with its handle
    private string GetText(IntPtr handle)
    {
        int maxLength = 512;
        IntPtr buffer = Marshal.AllocHGlobal((maxLength + 1) * 2);
        SendMessageW(handle, WM_GETTEXT, maxLength, buffer);
        string w = Marshal.PtrToStringUni(buffer);


       Marshal.FreeHGlobal(buffer);
            return w;
        }
    }
}