text box validation in c#

try this:


 if ((e.KeyChar < '0' || e.KeyChar > '9') && (e.KeyChar != '\b') && (e.KeyChar != '.'))
            {
                e.Handled = true;
            }
            else
            {
                e.Handled = false;
            }
            if (Char.IsControl(e.KeyChar))
            {
                e.Handled = false;
            }
            else if (Char.IsNumber(e.KeyChar) || e.KeyChar == '.')
            {
                TextBox tb = sender as TextBox;
                int cursorPosLeft = tb.SelectionStart;
                int cursorPosRight = tb.SelectionStart + tb.SelectionLength;
                string result = tb.Text.Substring(0, cursorPosLeft) + e.KeyChar + tb.Text.Substring(cursorPosRight);
                string[] parts = result.Split('.');
                if (parts.Length > 1)
                {
                    if (parts[1].Length > 2 || parts.Length > 2)
                    {
                        e.Handled = true;
                    }
                }
            }