Difference Between First() and FirstOrDefault() in LINQ

First()
Member

ID	Name	Year	Address	Income	UserName
1	PQR	2010-2011	C	50000	S123
2	PQR	2012-2013	C	180000	S123
3	XYZ	2013-2014	B	200000	S789
4	ABC	2013-2014	A	350000	S253

Var x=(from m in Member  

Where m.UserName=’S000’  

Select m.Name,m.Income,m.Year ).First()

In The Member table There Is no Such Record Which Will Match the expression so Above Query will Throw: InvalidOperationException: Sequence contains no elements

Var x=(from m in Member  
Where m.UserName=’s123’  

Select m.Name,m.Income,m.Year).First() 

Then You Will get The Result Like:

PQR

2010-11

50000

S123

1. First() returns First Element Of Sequence.
2. First() throws Exception when There IS No element Presnt In Table.

FirstORDefault():

When we Use FirstORDefault () in LINQ in Query Syntax Or Method Syntax, At that Time If we Do not Get any Record Corresponding To Criteria in Where Clause then It Will return Some Default Value (Null)


Var x=(from m in Member  
Where m.UserName=’S000’  

Select m.Name,m.Income,m.Year ).FirstOrDefault() 

In The Member table There Is no Such Record Which Will Match the expression so Above Query will Return Default value as Null but Not An Exception

We Can Handle This Exception In C# by using try Catch like:


try  
{  
   Var x=(from m in Member  
   Where m.UserName=’S000’  
   Select m.Name,m.Income,m.Year ). FirstOrDefault ()  
   If(x!=null)  
   {  
       Console.WriteLine(x.Name);  
   }  
   else  
   {  
     Console.WriteLine("No Record Found");  
   }  
}  
catch (Exception ex)  
{  
   Console.WriteLine(ex.Message);  

}  

1. FirstOrDefault () returns First Element Of Sequence.
   
2. FirstOrDefault () does not throws Exception when There IS No element Present in Table.