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Home >> Interview Question >> C# >> Post New Question Subscribe to Interview Questions

What is the difference between Convert.ToString() and .ToString() method.

Posted By :shankey     Posted Date :January 30, 2011    Points :15   Category :C# 
Have a look at the following program and its output

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

namespace ExampleOfString
{
class Program
{
static void Main(string[] args)
{
String UserName = null ;
try
{
//Below statement WILL THROW an exception as .ToString() does not handles null values
String strUserId = UserName.ToString();
}
catch (NullReferenceException ex)
{
Console.WriteLine("Error:{0}", ex.Message);
}

try
{
//Below statement WILL NOT THROW an exception as convert.tostring handles implicitly
String strUserId = Convert.ToString(UserName);
Console.WriteLine("UserName:{0}", strUserId);
}
catch (NullReferenceException ex)
{
Console.WriteLine("Error:{0}", ex.Message);
}
}
}
}

/*
Below is the output of the console application

Error:Object reference not set to an instance of an object.
UserName:
Press any key to continue . . .
*/

You can also find related Interview Question to What is the difference between Convert.ToString() and .ToString() method.  below: 

What is the difference between Convert.toString and .toString()
method?

  
Just to give an understanding of what the above question means see the below code :-

int val = 0;
MessageBox.Show(val.ToString());
MessageBox.Show(Convert.ToString(val));


We can convert the integer "val" using "val.ToString()" or "Convert.ToString" so what's the difference.

The basic difference between them is "Convert" function handles NULLS while "val.ToString()"
does not.

It will throw a NULL reference exception error. So as good coding practice using "Convert" is always safe. (More...)

What is Difference Between ToString() vs Convert.ToString() vs (string) cast

  
There is a simple but important difference between these three.

ToString() raise exception when the object is null

So in the case of object.ToString(), if object is null, it raise NullReferenceException.

Convert.ToString() return string.Empty in case of null object

(string) cast assign the object in case of null

So in case of
MyObject o = (string)NullObject;

But when you use o to access any property, it will raise NullReferenceException.
(More...)

What is the Difference between Convert.ToString() and .ToString()

  
Generally Convert.ToString() handles NULLs where as .ToString will return a Null Reference Exception.

So it would be good if we use Convert.ToString() all the time for casting purposes. (More...)

Difference between convert.Tostring() and .tostring()?

  
Convert.Tostring()
-- Support Null Value
.ToString()
-- Not support null value (More...)

What is difference between convert.tostring() and tostring()?

  
The main difference between ToString() and Convert.ToString() is,"Convert" function handles NULLS while "variable.ToString()" does not it will throw a NULL reference exception error. So as a good coding practice using "convert" is always safe.

Session["test_variable"] ="test";
Response.Write(Convert.ToString(Session["test_variable"])); //it will display "test"
Response.Write(Session["test_variable"].ToString());//it will display "test"

//ERROR will not come in above statement because declared sesssion contains a value

Session["test_variable"] = null;
Response.Write(Convert.ToString(Session["test_variable"])); //it will convert to blank value ,No erro will come
Response.Write(Session["test_variable"].ToString());//will not handle the NULL values and it throws a NULL Reference Exception e
(More...)

What is the difference between convert.to.string and .to.string() method?

  
Convert function handles nulls while i.string() does not it will throw a null reference exception error. (More...)

Difference between Int32.Parse,Convert.Int32

  
Int32.Parse Method:
-------------------
Converts the string representation of a number to its 32-bit signed integer equivalent.
-When s is a null reference, it will throw ArgumentNullException.
-If s is other than integer value, it will throw FormatException.
-When s represents a number out of range, it will throw OverflowException.

Convert.ToInt32(string):
-------------------------
Converts the specified string representation of 32-bit signed integer equivalent. This calls in turn Int32.Parse () method.
-When s is a null reference, it will return 0 rather than throw ArgumentNullException.
-If s is other than integer value, it will throw FormatException.
-When s represents a number out of range, it will throw OverflowException.

Int32.TryParse Method:
----------------------
Converts the specified string representation of 32-bit signed integer equivalent to out variable, and returns true if it is parsed successfully, false otherwise.
-When s is a null reference, it will return 0.
-If s is other than an integer value, the out variable will have 0.
-When s represents a number out of range, the out variable will have 0. (More...)

What is the difference between Session.Clear() and Session.RemoveAll() method?

  
Well, actually there is no difference. Session.RemoveAll() methods internally makes a call to Clear() method only.

Thanks. (More...)

What is difference between TransferRequest and Transfer method?

  
Transfer: Terminates execution of the current page and starts execution of provided URL.
TransferRequest : Performs an asynchronous execution of the provided URL. (More...)

Main Difference between Method and function?

  
Method which tied to a class where as function need not to be. In OOPS we can say there is no functions concept because all the method is tied to a class.

Function is available in procedural language, Scripting language that why we say JavaScript function etc. (More...)

What is the difference between method activity and event activity in WorkFlow ?

  
A method activity is one that performs an action, such as creating or updating a task. An event activity is one that runs in response to an action occurring. (More...)

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