Textbox left blank = freeze?

[redcodefinal]

Hi! I'm still a bit of a beginner to C# .Net 3.0 and I need some help. I have a program that takes two textbox inputs and adds them together. However when one is left blank it causes the program to freeze. I used a if(Textbox1.Text == null) condition but it still causes it to freeze. I believe I have to use catch and try but I don't know what the exception would be to catch! Anyone know what to do?

[Arjay]

Post the code where you adding the two listboxes together.

[redcodefinal]

Its just

int tb1;
int tb2;
int output;

tb1 = System.Int32.Parse(textBox1.Text);
tb2 = System.Int32.Parse(textBox2.Text);

output = tb1 + tb2;
textBox3.Text = output;

[rocky_upadhaya]

Try these statements

try
   {
   //your Code Here
  }

catch (FormatException) //Handles if You mistakely input String
            {
                MessageBox.Show("Error! Enter Correctly");
            }
            catch (ArgumentOutOfRangeException) /* Handles if You mistakely put value but variable is unable to store or in other words  it is out of range. This is useful for arrays index too*/
            {
                MessageBox.Show("Error! Enter Correctly");
            }

            catch (NullReferenceException) //Handles Empty textboxes or others.
            {
                MessageBox.Show("Error! Type Correctly");
            }

[boudino]

This could (should if TextBox is blank) fail with exception, but freeze? What exactly it does?

BTW, the condition is better to write

if(String.IsNullOrEmpty(Textbox1.Text))

(To be exact, I'm not sure if TextBox.Text can even be null, I think it is allways at least String.Empty (=""))

[rocky_upadhaya]

It is a good programming practice to use exceptional Handling. It solves not only the problem where input is empty but also take cares of other Possible errors...cheers....

[boudino]

Bad exception handling is worse than none.

[rocky_upadhaya]

Please explain what is wrong with the error handling codes posted by me above...