//实现只限制输入数字事件

        private void txtShowNum_KeyPress(object sender, KeyPressEventArgs e)

        {

            e.Handled = true;

            //0~9数字对应的keychar为：48~57，小数点为46，Backspace为8

            if((e.KeyChar>= && e.KeyChar<=)|| e.KeyChar==)

            {

                e.Handled = false;

            }

            if(e.KeyChar==)

            {

                if (txtShowNum.Text.Trim().Length <= )

                {

                    e.Handled = true;

                }

                else

                {

                    float f;

                    if(float.TryParse(txtShowNum.Text+e.KeyChar.ToString(),out f))

                    {

                        e.Handled = false;

                    }

                }

            }

        }