What is difference between First() vs FirstOrDefault()

Hello readers, I am sharing post about First() vs FirstOrDefault(). Here, you can find  difference between First and FirstOrDefault, When to use and different type of scenario with example.

First()

It returns First element of a sequence or a value from collection of elements. If there are no elements in the result than it will throws InvalidOperationException.

When to use: When more than 1 element is expected and you want only the first .

Examples

Following the Student Enityt where i will to perform query on that.

StudentId	Firstname	Lastname	DOB
1	Alok	Singh	12/8/1985
2	Anil	Singh	2/19/1984
3	Sachin	Kinra	8/30/1996
4	Cris	Moris	9/19/1981
5	Sahil	Joshi	3/4/1995
6	Rahul	Maurya	7/2/1969
7	Raj	Joshi	5/29/1984
8	King	George	1/9/1980
9	Michel	Jonhsan	1/27/1965

Query 1	Student.OrderBy(e => e. DOB) .First(e => e.Lastname == "Joshi")
Expected Result	There are multiple records where Lastname == Joshi. Should return the oldest one.
Actual Result	StudentId Firstname Lastname DOB 7 Raj Joshi 12/8/1985

Query 2	Student.OrderBy(e => e. DOB) .First(e => e.StudentId == 15)
Expected Result	There is no record with StudentId = 15. Should fail.
Actual Result	InvalidOperationException: Sequence contains no elements

FirstOrDefault()

It returns the first element of a sequence or default value of underlying type of generic collection. It does not throw InvalidOperationException if no element found.

When to use: When more than 1 element is expected and you want only the first. Also it is fine for the result to be empty.

Examples

Following the Student Enityt where i will to perform query on that.

StudentId	Firstname	Lastname	DOB
1	Alok	Singh	12/8/1985
2	Anil	Singh	2/19/1984
3	Sachin	Kinra	8/30/1996
4	Cris	Moris	9/19/1981
5	Sahil	Joshi	3/4/1995
6	Rahul	Maurya	7/2/1969
7	Raj	Joshi	5/29/1984
8	King	George	1/9/1980
9	Michel	Jonhsan	1/27/1965

Query 1	Student.OrderBy(e => e. DOB) .FirstOrDefault(e => e.Lastname == "Joshi")
Expected Result	There are multiple records where Lastname == Joshi. Should return the oldest one.
Actual Result	StudentId Firstname Lastname DOB 7 Raj Joshi 12/8/1985

Query 2	Student.OrderBy(e => e. DOB) .FirstOrDefault(e => e.StudentId == 15)
Expected Result	There is no record with StudentId = 15. Should return default value.
Actual Result	null