# Education is not limited to just classrooms. It can be gained anytime, anywhere... - Ravi Ranjan (M.Tech-NIT)

## Aggregation Operator: Sum

The Sum() method calculates the sum of numeric items in the collection.

The following example demonstrates Sum() on primitive collection.

Example: LINQ Sum() - C#

``````
IList<int> intList = new List<int>() { 10, 21, 30, 45, 50, 87 };

var total = intList.Sum();

Console.WriteLine("Sum: {0}", total);

var sumOfEvenElements = intList.Sum(i => {
if(i%2 == 0)
return i;

return 0;
});

Console.WriteLine("Sum of Even Elements: {0}", sumOfEvenElements );

``````

Output:

Sum: 243
Sum of Even Elements: 90

The following example calculates sum of all student's age and also number of adult students in a student collection.

Example: LINQ Sum() - C#

``````
IList<Student> studentList = new List<Student>>() {
new Student() { StudentID = 1, StudentName = "John", Age = 13} ,
new Student() { StudentID = 2, StudentName = "Moin",  Age = 21 } ,
new Student() { StudentID = 3, StudentName = "Bill",  Age = 18 } ,
new Student() { StudentID = 4, StudentName = "Ram" , Age = 20} ,
new Student() { StudentID = 5, StudentName = "Ron" , Age = 15 }
};

var sumOfAge = studentList.Sum(s => s.Age);

Console.WriteLine("Sum of all student's age: {0}", sumOfAge);

var numOfAdults = studentList.Sum(s => {

if(s.Age >= 18)
return 1;
else
return 0;
});

``````

Example: Sum in method syntax - VB.NET

``````
// Student collection
Dim studentList = New List(Of Student) From {
New Student() With {.StudentID = 1, .StudentName = "John", .Age = 13},
New Student() With {.StudentID = 2, .StudentName = "Moin", .Age = 21},
New Student() With {.StudentID = 3, .StudentName = "Bill", .Age = 18},
New Student() With {.StudentID = 4, .StudentName = "Ram", .Age = 20},
New Student() With {.StudentID = 5, .StudentName = "Ron", .Age = 15}
}

Dim sumOfAge = studentList.Sum(Function(s) s.Age)

Console.WriteLine("Total Age of Student: {0}", sumOfAge)

if(s.Age >= 18)
return 1
else
return 0
end if
end function)

``````

Output:

Total Age of Student: 87

Sum operator in query syntax:

Sum operator is Not Supported in C# Query syntax.

Example: Sum operator in query syntax - VB.Net

``````
// Student collection
Dim studentList = New List(Of Student) From {
New Student() With {.StudentID = 1, .StudentName = "John", .Age = 13},
New Student() With {.StudentID = 2, .StudentName = "Moin", .Age = 21},
New Student() With {.StudentID = 3, .StudentName = "Bill", .Age = 18},
New Student() With {.StudentID = 4, .StudentName = "Ram", .Age = 20},
New Student() With {.StudentID = 5, .StudentName = "Ron", .Age = 15}
}

Dim totalAge = Aggregate st In studentList Into Sum(st.Age)

Console.WriteLine("Sum of all student's age: {0}", totalAge);

``````

Output:

Sum of all student's age: 87