validate the user.

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 Validation_on_textbox
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            foreach (Control c1 in this.Controls)
            {
                if (c1 is TextBox)
                {
                    if (c1.Text == "")
                    {
                        MessageBox.Show("Name Field cannnot be blank");
                        c1.BackColor = Color.Orange;
                        textBox1.Focus();
                    }
                    else
                    {
                        MessageBox.Show("Correct");
                        c1.BackColor = Color.White;
                    }
                }
            }
            clear();
        }
        private void clear()
        {
            textBox1.Text = "";
        }
    }
}

hi,

you can refer to this some examples are there.

http://www.codeproject.com/Articles/13922/Validate-user-input-in-Windows-Forms

http://www.dotnetfunda.com/codes/code109-textbox-validation-in-windows-application-using-csharp.aspx