I'm using C# to make a Windows Form Application. My form has 4 labels, 4 text boxes, 2 buttons. I'm having trouble getting the area and perimeter. When I enter length and width and push calculate button, nothing shows in textbox for area and perimeter. Can you please explain what I'm doing wrong. This is my event handler code for my calculate button:

private void btnCalculate_Click(object sender, EventArgs e) {

double length, width,area,perimeter;

length = Convert.ToDouble(txtLength.Text);

width = Convert.ToDouble(txtWidth.Text);

area = length * width;

perimeter = (2 * length + 2 * width);

String txtArea = Convert.ToString(area);

btnCalculate.Text = Convert.ToString(perimeter);

Console.WriteLine(txtArea);

}