What is the difference between null & String.Empty

Can any one explain me what is the difference between below 2 statements.

string FirstName = null;

string FirstNmae = String.Empty;

When should I use which?
GouthamAnandAsked:
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Obadiah ChristopherCommented:
string.Empty provides better performance when it is used against something like

""

string FristName = ""; instead of this use string FirstName = string.Empty;

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slinkygnPresidentCommented:
string FirstName = string.Empty;

creates a string object with value "".  Length is zero, etc.

string FirstName = null;

means FirstName does not refer to an object.

If you're just going to assign a different string object to FirstName, there's no point in assigning the "" null-string object to it -- might as well use string FirstName = null.

If you want to start, for example, concatenating onto FirstName, you'll want it to be a valid string object, so you'd use string FirstName = string.Empty.
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rpkhareCommented:
Read below:


======== Courtesy: MSDN =============
Null Strings and Empty Strings

An empty string is an instance of a System.String object that contains zero characters. Empty strings are used quite commonly in various programming scenarios to represent a blank text field. You can call methods on empty strings because they are valid System.String objects. Empty strings are initialized like this:


string s = "";

By contrast, a null string does not refer to an instance of a System.String object and any attempt to call a method on a null string results in a NullReferenceException. However, you can use null strings in concatenation and comparison operations with other strings. The following examples illustrate some cases in which a reference to a null string does and does not cause an exception to be thrown:


string str = "hello";
string nullStr = null;
string emptyStr = "";

string tempStr  = str + nullStr; // tempStr = "hello"
bool b = (emptyStr == nullStr);// b = false;
emptyStr + nullStr = ""; // creates a new empty string
int I  = nullStr.Length; // throws NullReferenceException
==============================================

Check this link:
http://msdn.microsoft.com/en-us/library/ms228362(VS.80).aspx
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Gyanendra SinghArchitectCommented:
on simple way
When a string variable is set to null, this means that it doesn't currently refer to a string instance.
An empty string is a string instance which contains no characters. In other words its Length property is 0.
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GouthamAnandAuthor Commented:
Thank you.
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