RichTextBox Selection Highlight

Question

Is there a possibility that after selection made by user, every selected letter displays it's original color? And not always white as it's by default?

I want to achieve something like that which you can see in wordpad.

instead of which you see in RichTextBox.

Answer 1

For anyone having problem with Visual Studio 2019 and exception "Class already exists" as mentioned in Hunar's comment I modified slightly code to load library only once and that solved issue for me.

using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Windows.Forms;

[DesignerCategory("Code")]
public class RichTextBox5 : RichTextBox
{
    [DllImport("kernel32.dll", EntryPoint = "LoadLibraryW", CharSet = CharSet.Unicode, SetLastError = true)]
    private static extern IntPtr LoadLibraryW(string s_File);

    private static readonly object libraryLoadLock = new object();
    private static bool libraryLoadFlag;

    public static IntPtr LoadLibrary(string s_File)
    {
        var module = LoadLibraryW(s_File);
        if (module != IntPtr.Zero)
        {
            return module;
        }
        var error = Marshal.GetLastWin32Error();
        throw new Win32Exception(error);
    }

    protected override CreateParams CreateParams
    {
        get
        {
            var cp = base.CreateParams;
            try
            {
                lock (libraryLoadLock)
                {
                    if (!libraryLoadFlag)
                    {
                        LoadLibrary("MsftEdit.dll"); // Available since XP SP1
                        libraryLoadFlag = true;
                    }
                }
                cp.ClassName = "RichEdit50W";
            }
            catch { /* Windows XP without any Service Pack.*/ }
            return cp;
        }
    }
}

Sorry for answering this way, but due to insufficient reputation points I was able only to post an answer.

Answer 2

You can use the latest version of RichTextBox that is RICHEDIT50W, to do so you should inherit from standard RichTextBox and override CreateParams and set the ClassName to RICHEDIT50W:

Code

using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Windows.Forms;
public class ExRichText : RichTextBox
{
    [DllImport("kernel32.dll", EntryPoint = "LoadLibraryW", 
        CharSet = CharSet.Unicode, SetLastError = true)]
    private static extern IntPtr LoadLibraryW(string s_File);
    public static IntPtr LoadLibrary(string s_File)
    {
        var module = LoadLibraryW(s_File);
        if (module != IntPtr.Zero)
            return module;
        var error = Marshal.GetLastWin32Error();
        throw new Win32Exception(error);
    }
    protected override CreateParams CreateParams
    {
        get
        {
            var cp = base.CreateParams;
            try
            {
                LoadLibrary("MsftEdit.dll"); // Available since XP SP1
                cp.ClassName = "RichEdit50W";
            }
            catch { /* Windows XP without any Service Pack.*/ }
            return cp;
        }
    }
}

Screenshot

Note:

• I could see the class of RichTextBox of wordpad using Spy++ thanks to this ancient useful visual studio tool.

• If you had any problem with RICHEDIT50W in your os, you can open Spy++ and WordPad and then select the RichTextBox of it and see what's the class name.

• When I searched about applying the RICHEDIT50W class to my control, I reached to this great post of @Elmue, Thanks to him.