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

Posted By :Sajid P K     Posted Date :November 11, 2010    Points :10   Category :.NET Framework 
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.


You can also find related Interview Question to What is Difference Between ToString() vs Convert.ToString() vs (string) cast  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 the difference between Convert.ToString() and .ToString() method.

  
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 . . .
*/ (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 String.Empty and ""

  
The main difference is lies on memory management.

String.Empty will not create any object of string where as "" (Double Quote or Empty Quote) will create a new object in the memory for the checking the objects. (More...)

How do I convert a numeric type to a string?

  
Call Sytem.Object.ToString(). For example, if the variable count is an integer, write the following:
string text = count.ToString(); (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...)

difference between string and StringBuilder?

  
String is immutable & StringBuilder is mutable.
Means we can add, remove or append the words in stringbuilder but not in string. And stringbuilder have larger range of storing than string. (More...)

Difference between System.String and System.StringBuilder classes?

  
-- System.String is immutable; System.StringBuilder can have mutable string where a variety of operations can be performed. (More...)

What is the difference between string and stringbuilder?

  
Objects of type stringBuilder are mutable, whereas objects of string are immutable (More...)

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