i dont know how much new you are to .net because the question u asked doesnt show anything information from u..
i have added a basic program to find the greatest of three numbers
Add three textboxes(name them as txtA,txtB,txtC)and one Button COntrol in Form1.cs[design] and in buttonclick event write this code (in form1.cs)and press F5
private void button1_Click(object sender, EventArgs e)
{
int a = Int32.Parse(txtA.Text);
int b = Int32.Parse(txtB.Text);
int c = Int32.Parse(txtC.Text);
if ((a > b) && (b > c))
MessageBox.Show("A is Greatest" + txtA.Text);
else if ((a < b) && (b > c))
MessageBox.Show("B is the Greatest" + txtB.Text);
else if ((a < b) && (b < c))
MessageBox.Show("C is the greatest" + txtC.Text);
else if ((a == b) || (b == c) || (a == c))
MessageBox.Show("two values or all the values are Same");
}