Automatically put decimal for currency format in TextBox when typing

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Introduction

This is a cool code to use TextBox for entering currency data. It will automatically add decimal when typing on the TextBox. The backspace and delete key is used to delete a number from the TextBox.

The source code is:

string str="";
private void textBox1_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)
{
  int KeyCode = e.KeyValue;

  if(!IsNumeric(KeyCode))
  {
    e.Handled=true;
    return;
  }
  else
  {
    e.Handled=true;
  }
  if(((KeyCode==8)||(KeyCode==46))&&(str.Length>0))
  {
    str = str.Substring(0,str.Length-1);
  }
  else if(!((KeyCode==8)||(KeyCode==46)))
  {
    str = str+Convert.ToChar(KeyCode);
  }
  if(str.Length==0)
  {
    textBox1.Text = "";
  }
  if(str.Length==1)
  {
    textBox1.Text = "0.0"+str;
  }
  else if(str.Length==2)
  {
    textBox1.Text = "0."+str;
  }
  else if(str.Length>2)
  {
    textBox1.Text = str.Substring(0,str.Length-2)+"."+
                    str.Substring(str.Length-2);
  }
}

private bool IsNumeric(int Val)
{
  return ((Val>=48 && Val<=57) || (Val == 8) ||(Val==46));
}

private void textBox1_KeyPress(object sender, 
        System.Windows.Forms.KeyPressEventArgs e)
{
  e.Handled=true;
}