If/else instead of try/catch

Introduction

In this tip I tell you how to use if/else instead of try/catch.

Try/catch

To handle exceptions, the try/catch block is very helpful in C#:

try
{
    // code to try
} 
catch (Exception e)
{
   // catch an exception
}

There're a few exceptions that we can prevent with an if/else statement.

Preventing exceptions with if/else

IndexOutOfRangeException

One of the exceptions that we can prevent with an if/else statement, is the IndexOutOfRangeException.
Instead of this:

int[] array = new int[10] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int j = Convert.ToInt32(Console.ReadLine());
try
{
   int i = array[j]; // this can throw an error
}
catch (IndexOutOfRangeException)
{
   Console.WriteLine("Index out of range");
}

You can do this:

int[] array = new int[10] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int j = Convert.ToInt32(Console.ReadLine());
if (array.Length > j && j > -1)
{
     int i = array[j]; // now, this can't throw an error
}
else
{
     Console.WriteLine("Index out of range");
}

NullReferenceException

Another exception is the NullReferenceException. With an if statement, you can check for null.

string str = null;
if (str != null)
{
    str.Replace("a","b"); // this can't throw an error
}
else
{
    Console.WriteLine("str is null!");
}

DivideByZeroException

An DivideByZeroException throws when you try to divide a number by zero. That's also an exception that we can prevent with if/else:

int _int1 = Convert.ToInt32(Console.ReadLine());
int _int2 = Convert.ToInt32(Console.ReadLine());
int result = 0;
if (_int2 != 0)
{
     result = _int1 / _int2;
}
else
{
   Console.WriteLine("Can't divide by zero!");
}

ObjectDisposedException

You can't check whether a object is disposed or not, but the Control class in Windows Forms has a IsDisposed property that you can use. 

Control c = new Control();
c.Dispose();
if (!c.IsDisposed)
{
   c.Controls.Add(new Control());
}
else
{
   MessageBox.Show("Control is disposed!");
}

FileNotFoundException

The FileNotFoundException is also an exception that you can prevent with if/else.

string filename = Console.ReadLine();
if (System.IO.File.Exists(filename))
{
    string content = File.ReadAllText(filename);
}
else
{
    Console.WriteLine("File not found.");
}

Why if/else and not try/catch?

Speed 

If you've one if/else block instead of one try/catch block, and if an exceptions throws in the try/catch block, then the if/else block is faster (if/else block: around 0.0012 milliseconds, try/catch block: around 0.6664 milliseconds). If no exception is thrown with a try/catch block, then a try/catch block is faster. But if you use 100 try/catch blocks in your program, and if one exceptions throws, then 100 if/else blocks is faster.

Skipping immediately

If you've a try/catch block where you divide by zero, and you do a few things before you divide, then some useless code is running. If you've a if/else block, then all useless code is skipped immediately, then you don't need to wait until the division.