how to handle null reference and out of bound exceptions

Question

1.00/5 (2 votes)

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C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.ServiceModel.Web;
using System.Text;
using System.Data.SqlClient;
using System.Data;

namespace GridExample
{
    // NOTE: You can use the "Rename" command on the "Refactor" menu to change the class name "Service1" in code, svc and config file together.
    public class Service1 : IService1
    {
        
        public CompositeType GetDataUsingDataContract(CompositeType composite)
        {
            if (composite == null)
            {
                throw new ArgumentNullException("composite");
            }
            if (composite.BoolValue)
            {
                composite.StringValue += "Suffix";
            }
            return composite;
        }


        public List<register> GetDetails(string id)
        {
             List<register> lstrs = new List<register>();
             try
             {


                 SqlConnection con = new SqlConnection("Data Source=2X12Soft;Initial Catalog=test;User ID=sa;Password=bharat");
                 con.Open();
                 SqlCommand cmd = new SqlCommand("select * from depttable", con);

                 SqlDataReader reader = cmd.ExecuteReader();

                 while (reader.Read())
                 {
                     register rs = new register();
                     rs.id = reader["deptid"].ToString();

                     rs.name = reader["deptdame"].ToString();

                     lstrs.Add(rs);
                 }

                 con.Close();

             }
             catch (NullReferenceException ex)
             {

                 nullreference nre = new nullreference();
                 nre.Error = ex.Message;
                 nre.Details = "null reference";
                 throw new FaultException<nullreference>(nre);
             }
             catch (Exception ex)
             {
                 nullreference nre = new nullreference();
                 nre.Error = ex.Message;
                 nre.Details = "null reference";
                 ThrowsTypedCLRFaultException();
                 
             }
            return lstrs;
            
        }
       

        public string ThrowsTypedCLRFaultException()
        {
            throw new FaultException("Error while dividing number");
            //throw new Exception("ThrowsCLRException: IndexOutOfRangeException");//here i am getting the error. how to throw  this type of exception.this is a wcf service and host is windows form
        }
    }

}

Posted 8-Jun-15 0:34am

venkanna t

Updated 8-Jun-15 1:22am

RajeeshMenoth

v2

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Afzaal Ahmad Zeeshan · Answer 1 · 2015-06-08T01:06:00

They are different kind of errors, but resemble in a way that they both tell you that you are trying to reference an object that doesn't exist.

NullReferenceException[^]

This exception means that the object being used or operated on, doesn't exist. Possible candidates are type-mismatch (Object reference not set to an instance of object) and sometimes when you declare a variable but forget to initialize it with a valid value. It can be handled using the try catch block, but good way to handle it is to initialize the variables and to make sure that they are not null; that they do exist in the memory.

My blog post about null exceptions: What is a null error in code Execution[^]

IndexOutOfBoundsException

Doesn't exist in .NET framework, it is a Java based exception. In .NET framework there is a IndexOutOfRangeException[^]. Which means that you are trying to reference an object that doesn't exist in the limit of the array (or collection).

C#

int[] arr = { 1, 2, 3, 4, 5 }; // Length = 5
Console.WriteLine(arr[10]); // Exception raised

It can be minimize by using the try catch, but the good way to handle it is to make sure that you do not reference an object out side the bounds. Always check the count of the objects in the collection and then perform respectively.

C#

int[] arr = { 1, 2, 3, 4, 5 }; // Length = 5;
if(arr.Length == 5) {
   Console.WriteLine(arr[4]); // index 4 == element 5
}

It is never good way to let the framework always handle the exceptions, you need to know what you are doing. Although try catch is a good way to ignore unexpected application breakage, but it is not a good way to develop the software. You need to handle the problems yourself or at least know where exceptions are going to be raised to handle the scenarios. if...else is a good candidate.

Andy Lanng · Answer 2 · 2015-06-08T00:47:00

You should handle the issue rather than catching the error.

for example:

C#

if(myvar==null)
  return "error_01";

string[] myvars = myvar.split(',')

if(myvars.length==0)
  return "error_02";

I would never use try/catch to handle null reference or indexoutofrange errors!

Also, you shouldn't throw (or allow to be thrown) exceptions in a webservice because they are so difficult to handle in the calling method. Web Service exceptions should only be thrown if the webservice is missing or down.

Return a simple error code instead. I use a base response object with a response code ("00" for success) and the error message.

how to handle null reference and out of bound exceptions

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