namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Regex r1 = new Regex(@"^.$");
if ((r1.IsMatch(textBox1.Text)))
{
MessageBox.Show("plz enter Valid value");
}
}
}
}