function return values c# - c#-4.0

Question

I am trying to get to grips with C# having not coded for many years and my previous experience being in ANSI C.
I have read a number of books and searched online but one aspect is evading me and I am hoping someone here can help.
In the past I would declare a function and if there was a possibility of something not happening within the function (i.e. file not found etc.) declare the return to be an integer. I would then return 0 if all was well and a value if not. The value would correspond to where the function failed to execute fully and I could branch accordingly from where I called it.
if(function1())
{
// all my error stuff, maybe a switch/case etc.
}
All the examples I have found in C# seem to avoid this technique and I was hoping to get some understanding here.
Thanks in anticipation.
(I know I am a fossil). :)

Answer 1

Exceptions are the approach you use in C# and similar languages.
It goes like this:
try
{
function();
}
catch(FileNotFoundException e)
{
// File not found
}
catch(UnauthorizedAccessException e)
{
// User doesn't have right to access file
}
// etc...
To make this work, function shouldn't return a status code but instead throw an exception in case of an error.
Please note that the exceptions I illustrated in the code block above are thrown by the framework if you try to access a file and one of those errors is happening. So you don't actually have to do this yourself.
Furthermore, in C# there is no implicit conversion from integral values to bool, i.e. if(function()) is invalid, if function returns an int. You would need to write it like this:
if(function() != 0)
{
// all your error stuff
}

Answer 2

There's nothing to stop you doing this (though there are better ways of handling the errors - exceptions for example).
If you do want to carry on with this approach, the biggest problem you are having is that in C# you can't treat an integer as a boolean so your if test won't compile. What you need is:
if (function1() != 0)
{
}
But to check the value you'd need:
int result = function1();
switch (result)
{
case 1:
// Handle this case
break;
case 2:
// Handle this case
break;
default:
// All OK
break;
}
It would be better to return an enumerated type for each error case so that you don't have magic numbers, but exceptions are the way to go:
try
{
function1();
}
catch (SpecificException1 e1)
{
// Handle this case
}
catch (SpecificException2 e2)
{
// Handle this case
}
What you shouldn't have is a general exception handler:
catch (Exception e)
{
}
This just hides other potential problems.

Answer 3

If you want to follow that pattern of checking return value instead of managing errors, you better use enumarations than plain numbers.
For example:
public enum ResultType
{
Error = 0,
Success,
Waiting
}
public ResultType function()
{
if (still_waiting)
return ResultType.Waiting;
if (error_has_occured)
return ResultType.Error;
return ResultType.Success;
}
public void Main()
{
ResultType result = function();
switch (result)
{
case ResultType.Success:
MessageBox.Show("all is good");
break;
case ResultType.Waiting:
MessageBox.Show("still waiting...");
break;
case ResultType.Error:
MessageBox.Show("error has occurred");
break;
}
}
Behind the scenes, it's still using numbers but you put some meaning to each number.

Answer 4

if(function()==1)
{
}
int function()
{
int returnVal =0;
// do stuff
// if true return returnVal =1 else set returnVal =0;
return returnVal;
}