Hello readers, I am sharing post about Single() vs SingleOrDefault(). Here, you can find difference between Single and SingleOrDefault , When To use and different type of scenario with example.
Single()
It returns a single, specific element of a sequence if element match found. If none or more than one match found for that element in the collection then an exception is thrown.
When to use: If exactly 1 element is expected; not 0 or more than 1.
Examples
Following the Student Entity where we will 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. Single ( e => e. StudentId == 1 )
Expected Result
There is one record where StudentId == 1. It will return this record.
Result
StudentId Firstname Lastname DOB
1
Alok
Singh
12/8/1985
Query 2
Student. Single ( e => e. Lastname == "Joshi" )
Expected Result
There are multiple records where Lastname == Joshi. Should fail.
Actual Result
InvalidOperationException: Sequence contains more than one element
Student. Single ( e => e. StudentId == 15 )
Expected Result
There is no record with StudentId == 15. Should fail.
Actual Result
InvalidOperationException: Sequence contains no elements
SingleOrDefault()
It returns a single specific element from a collection of elements if there is any match found. If no match is found for that element in the collection, A default value is returned. If there is more than one match found for that element in the collection then an exception is thrown.
When to use: When 0 or 1 elements are expected.
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. SingleOrDefault ( e => e. StudentId == 1 )
Expected Result
There is only one record where StudentId == 1. Should return this record.
Actual Result
StudentId Firstname Lastname DOB
1
Alok
Singh
12/8/1985
Query 2
Student. SingleOrDefault ( e => e. Lastname == "Joshi" )
Expected Result
There are multiple records where Lastname == Joshi. Should fail.
Actual Result
InvalidOperationException: Sequence contains more than one element
Query 3
Student. SingleOrDefault ( e => e. StudentId == 15 )
Expected Result
There is no record with StudentId = 15. Should return default value.
Actual Result
null
