C# tutorial-C# Exception handling

C# Exception handling

C# provides try...catch block to catch any errors that may occur during programs execution. In the below example, we use the try...catch block to catch the error that is comes from trying to access an element of the array by using its index which in fact the element does not exist.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace ConsoleApplication1
{
      class Program
     {

         static void Main(string[] args)
              {
                int[] arr = {1, 2, 3, 4, 5};
                int i;
                try{
                for(i=0;i<=arr.Length ;i++)
                Console.WriteLine(arr[i]);
                }catch(IndexOutOfRangeException e){}

      }
   }

}

The IndexOutOfRangesException is an exception class for handling the error that is generated from accessing an element that does not exist in an array.

If you are not sure the types of errors to be catch you can use the Exception class. The code above can be rewritten to:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace ConsoleApplication1
{
     class Program
     {

       static void Main(string[] args)
         {
           int[] arr = {1, 2, 3, 4, 5};
           int i;
           try{
              for(i=0;i<=arr.Length ;i++)
              Console.WriteLine(arr[i]);
           }catch(Exception e){}

           Console.Read();}

    }
}

If you want to show a friendly message when an error occurs, you can write the message in catch(){message} block.

Example:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace ConsoleApplication1
{
      class Program
     {
  
        static void Main(string[] args)
         {

            int[] arr = {1, 2, 3, 4, 5};
            int i;
            try
               {
                 for (i = 0; i <= arr.Length; i++)
                 Console.WriteLine(arr[i]);
                }
             catch (Exception e) { Console.WriteLine("You may access an    array element that doesn't exist."); }


             Console.Read();
         }

    }
}

Using finally keyword

The finally keyword is used to execute lines of code in its block regardless to the errors that may occur. The code in its block(finally{code}) will always execute whether an error exists or not.

Example:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace ConsoleApplication1
{
class Program
{
public static int pos=0;
static void Main(string[] args)
{

int[] arr = {1, 2, 3, 4, 5};
int i;
try
{
for (i = 0; i <= arr.Length; i++)
Console.WriteLine(arr[i]);
}
catch (Exception e) { }
finally
{
Console.WriteLine("The program ended...");
}

Console.Read();
     }


}

}