Q:

How to move the cursor between textboxes using arrow keys?

I have several TextBoxes and I want the cursor to move from one TextBox to another using arrow keys.
How can I do that?
It looks like this, also the tap moves vertically which is weird.
Thanks.

A:

You can override the form's ProcessCmdKey method, and handle the key press and focusing on text boxes in it.
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;

namespace TextBoxes
{
    public partial class Form1 : Form
    {
        List<TextBox[]> _textBoxes;
        public Form1()
        {
            InitializeComponent();

            //Getting a 2 dimentional structure to hold textboxes
            this._textBoxes= new List<TextBox[]>();

            TextBox[] row1 = new TextBox[4];
            row1[0] = textBox1;
            row1[1] = textBox2;
            row1[2] = textBox3;
            row1[3] = textBox4;

            TextBox[] row2 = new TextBox[4];
            row2[0] = textBox5;
            row2[1] = textBox6;
            row2[2] = textBox7;
            row2[3] = textBox8;

            TextBox[] row3 = new TextBox[4];
            row3[0] = textBox9;
            row3[1] = textBox10;
            row3[2] = textBox11;
            row3[3] = textBox12;

            TextBox[] row4 = new TextBox[4];
            row4[0] = textBox13;
            row4[1] = textBox14;
            row4[2] = textBox15;
            row4[3] = textBox16;

            this._textBoxes.Add(row1);
            this._textBoxes.Add(row2);
            this._textBoxes.Add(row3);
            this._textBoxes.Add(row4); 
        }

         /// <summary>
         /// Processes a command key.
         /// </summary>
         /// <param name="msg">A <see cref="T:System.Windows.Forms.Message"/>, passed by reference, that represents the Win32 message to process.</param>
         /// <param name="keyData">One of the <see cref="T:System.Windows.Forms.Keys"/> values that represents the key to process.</param>
         /// <returns>
         /// true if the keystroke was processed and consumed by the control; otherwise, false to allow further processing.
         /// </returns>
        protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
        {
            //A key was pressed! 
            Control activeCtrl = this.ActiveControl;
            TextBox txb = activeCtrl as TextBox;
            //Handle it only if it was sent when a textbox was focused
            if (txb != null)
            {
                int row;
                int column;
                //find out which text box is currently active
                this.GetTextBoxIndexes(txb, out row, out column);

                //change indexes according to key stroke
                if (keyData == Keys.Up)
                {
                    row--;
                }
                else if (keyData == Keys.Down)
                {
                    row++;
                }
                else if (keyData == Keys.Left)
                {
                    column--;
                }
                else if (keyData == Keys.Right)
                {
                    column++;
                }
                //Make sure we are not in negative / out of ranfe index
                row = Math.Abs(row + 4) % 4;
                column = Math.Abs(column + 4) % 4;

                //focus requested text box
                TextBox slected = this._textBoxes[row][column];
                slected.Focus();

            }
            //don't forget not to break the chain...
            return base.ProcessCmdKey(ref msg, keyData);
        }

        /// <summary>
        /// Gets the text box indexes.
        /// </summary>
        /// <param name="txb">The texbox.</param>
        /// <param name="row">The out row index.</param>
        /// <param name="column">The out column index.</param>
        private void GetTextBoxIndexes(TextBox txb, out int row, out int column)
        {
            row = -1;
            column = -1;
            for (int rowIdx = 0; rowIdx < this._textBoxes.Count; rowIdx++)
            {
                TextBox[] currRow = this._textBoxes[rowIdx];
                for (int colIdx = 0; colIdx < currRow.Length; colIdx++)
                {
                    TextBox currTextBox = this._textBoxes[rowIdx][colIdx];
                    if (currTextBox.Equals(txb))
                    {
                        row = rowIdx;
                        column = colIdx;
                        return;
                    }
                }
            }
        }
    }
}

A:

The following solution works if there is some text in the text boxes.
First create a KeyDown event handler:
private void textBoxLeft_KeyDown(object sender, KeyEventArgs e)
{
    if (e.KeyCode.Equals(Keys.Right))
    {
        e.Handled = true;
        //SendKeys.Send("{TAB}");
        textBoxRight.Focus();
    }
}

private void textBoxRight_KeyDown(object sender, KeyEventArgs e)
{
    if (e.KeyCode.Equals(Keys.Left))
    {
        e.Handled = true;
        //SendKeys.Send("+{TAB}");
        textBoxLeft.Focus();
    }
}

