how to navigate to previous letter in a single word

Hi muskesh009singh,

From your comment I'm assuming you want to do something like jumping in the text with special keyboard inputs. I created an example with an possible approach (maybe it's not exactly what you want, but I think you could adapt it - if you like it). Just copy to a C# 4 Forms project and replace Program.cs with the following code:

using System;
using System.Windows.Forms;

namespace NavigateToLetter
{
    static class Program
    {
        [STAThread]
        static void Main()
        {
            // Create a Form with a TextBox
            Form form = new Form();
            form.Text = "NavigateToLetter";
            TextBox textbox = new TextBox();
            textbox.Multiline = true;
            textbox.Dock = DockStyle.Fill;
            form.Controls.Add(textbox);
            // We handle the PreviewKeyDown event to jump to a new cursor
            // position on entered "input", this could be any key-combination
            //(NUM block, function keys, letters, ...)
            textbox.PreviewKeyDown +=
            delegate(object sender, PreviewKeyDownEventArgs e)
            {
                // ... so how to control the jumping while typing -
                // hmm.. lets take the function keys
                const int iF1_KEY = 112; // the F1 key
                const int iF24_KEY = 135; // the F24 key
                //
                int iKey = (int)e.KeyCode; // so grab the pressed key's code
                // ... and look if it's a function key
                // (we use the Keys enumaration values to shorten the code)
                if (iKey >= iF1_KEY && // the F1 Key 
                    iKey <= iF24_KEY) // the F24 Key (if you have a keyboard
                                         // with that many Function-Keys)
                {
                    string strWord = String.Empty; // the current word.
                    int iIndexOfLastSpace = textbox.Text.LastIndexOf(' ');

                    // Where is the last word?
                    if (iIndexOfLastSpace < 0) // no previous words found
                    {
                        // so we assume we are on the first word
                        strWord = textbox.Text;
                    }
                    else
                    {
                        // let's take the string starting from the last space as
                        //current word
                        strWord = textbox.Text.Substring(iIndexOfLastSpace + 1);
                    }

                    // do we have a word now?
                    if (!String.IsNullOrEmpty(strWord))
                    {
                        // lets think about the jumping:
                        // get the new cursor position the user gave us
                        int iEnteredPosition = iKey - iF1_KEY;
                        // but, is the word long enough?
                        // (else we stay on the current cursor position)
                        if (strWord.Length >= iEnteredPosition)
                        {
                            // calculate the new cursor position
                            // (begin of last word + entered position)
                            int iNewPosition = textbox.Text.Length -
                                               strWord.Length + iEnteredPosition;
                            // and finally: set the cursor position 
                            textbox.Select(iNewPosition, 0);
                        }
                    }
                }
            }; 
            // Ok, let's run the form and test it!
            Application.Run(form);
        }
    }
}