Aggregation Operator: Average

Average extension method calculates the average of the numeric items in the collection. Average method returns nullable or non-nullable decimal, double or float value.

The following example demonstrate Agerage method that returns average value of all the integers in the collection.

Example: Average method - C#

IList<int> intList = new List<int>>() { 10, 20, 30 };

var avg = intList.Average();

Console.WriteLine("Average: {0}", avg);

You can specify an int, decimal, double or float property of a class as a lambda expression of which you want to get an average value. The following example demonstrates Average method on the complex type.

Example: Average operator in method syntax 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 avgAge = studentList.Average(s => s.Age);

Console.WriteLine("Average Age of Student: {0}", avgAge);

Example: Average operator in method syntax VB.Net

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 avgAge = studentList.Average(Function(s) s.Age)

Console.WriteLine("Average Age of Student: {0}", avgAge)

Output:
Average Age of Student: 17.4

The Average operator in query syntax is Not Supported in C#. However, it is supported in VB.Net as shown below.

Example: Average operator in query syntax VB.Net

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 avgAge = Aggregate st In studentList Into Average(st.Age)

Console.WriteLine("Average Age of Student: {0}", avgAge)

Output:
Average Age of Student: 17.4

Learn about another aggregate operator - Count in the next section.