Math.Abs() Method Compiling Error

[maheshwag]

here is my code:

  private void button1_Click(object sender, EventArgs e)
        {
 
            decimal? t1 = null;
            decimal? t2 = null;
            decimal? t3 = null;
            decimal res = 0;
            t1 = Convert.ToDecimal(textBox1.Text);
            t2 = Convert.ToDecimal(textBox2.Text);
            t3 = Convert.ToDecimal(textBox3.Text);
            res = Math.Abs(t1 + t2 - t3);
            textBox4.Text = res.ToString();
 
        }
 
 

Which is throw compilling error like:
1. "The best overloaded method match for System.Math.Abs(sbyte)' has some invalid arguments"

2. "Argument'1' cannot convert from decimal to sbyte"

Actually i am trying to remove negative sign from the result of calculation. e.g.

textbox1.text value = 10
textbox2.text value = 10
textbox3.text value = 40

Then Result is -20, I want to remove '-' sign from the result.

How to solve it?.

[Christian Binder]

Because t1, t2 and t3 are of type Nullable<decimal>, their addition also returns an Nullable<decimal> and there's no overload for Math.Abs which takes a Nullable<decimal>. You have to convert it back to decimal.

res = Math.Abs((decimal)(t1 + t2 - t3));
//OR
res = Math.Abs((t1 + t2 - t3).Value);
 

[maheshwag]

You are very right but there is problem. when data on textbox null then it's fire error like " Input string was in not correct format"

how to overcome from this nullable type problem please suggest.

[Christian Binder]

You should use try-catch, so invalid strings don't cause the application to exit/throw error to the user.

What do you want to do if you gat wrong string, e.g. due to empty textbox?
Eighter you set the value to zero (or anything else) or you stop computation. You have to decide that.

This were the two ways:
(the variables declaration/init-part is omitted)

// ...
  try { t1 = Convert.ToDecimal(textBox1.Text); } catch {}
  try { t2 = Convert.ToDecimal(textBox2.Text); } catch {}
  try { t3 = Convert.ToDecimal(textBox3.Text); } catch {}
 
// First way, take zero instead of wrong input
  res = Math.Abs(t1 ?? 0 + t2 ?? 0 - t3 ?? 0)
  textBox4.Text = res.ToString();
 
// Second way, say "error" if any input was wrong
  if(t1.HasValue && t2.HasValue && t3.HasValue) {
    res = Math.Abs(t1.Value + t2.Value - t3.Value)
    textBox4.Text = res.ToString();
  } else 
    textBox4.Text = "Wrong input!";
 

[Curtis Rutland]

As an alternative to using Convert.To methods in a try statement, you can also use the TryParse method. The page I linked has examples for it's usage with decimals.