How to Exit a Method without Exiting the Program?

Question

I am still pretty new to C# and am having a difficult time getting used to it compared to C/CPP.

How do you exit a function on C# without exiting the program like this function would?

if (textBox1.Text == "" || textBox1.Text == String.Empty || textBox1.TextLength == 0)     textBox3.Text += "[-] Listbox is Empty!!!!\r\n"; System.Environment.Exit(0); 

This will not allow return types and if left alone it will keep going on through the function unstopped. Which is undesirable.

Answer 1

There are two ways to exit a method early (without quitting the program):

• Use the return keyword.
• Throw an exception.

Exceptions should only be used for exceptional circumstances - when the method cannot continue and it cannot return a reasonable value that would make sense to the caller. Usually though you should just return when you are done.

If your method returns void then you can write return without a value:

return; 

---

Specifically about your code:

• There is no need to write the same test three times. All those conditions are equivalent.

• You should also use curly braces when you write an if statement so that it is clear which statements are inside the body of the if statement:

  if (textBox1.Text == String.Empty) {     textBox3.Text += "[-] Listbox is Empty!!!!\r\n"; } return; // Are you sure you want the return to be here?? 

• If you are using .NET 4 there is a useful method that depending on your requirements you might want to consider using here: String.IsNullOrWhitespace.

• You might want to use Environment.Newline instead of "\r\n".
• You might want to consider another way to display invalid input other than writing messages to a text box.

Answer 2

In addition to Mark's answer, you also need to be aware of scope, which (as in C/C++) is specified using braces. So:

if (textBox1.Text == "" || textBox1.Text == String.Empty || textBox1.TextLength == 0)     textBox3.Text += "[-] Listbox is Empty!!!!\r\n"; return; 

will always return at that point. However:

if (textBox1.Text == "" || textBox1.Text == String.Empty || textBox1.TextLength == 0) {     textBox3.Text += "[-] Listbox is Empty!!!!\r\n";     return; } 

will only return if it goes into that if statement.