Learn LINQ with C#, Language Integrated query with different Data Source

# LINQ Sum method Example

Learn how to use SUM method in LINQ Query using C#

## SUM method in LINQ Query C#

`Enumerable.Sum` is extension method, it sum of numeric values of any collection, Sum method comes under `System.Linq` namespace

Let's look at some examples below

Sum for Numeric Data Types
Total sum of values of all integer numbers in the list.

```var _numbers = new List<int> { 10, 55, 5, 19, 9, 2};
Console.WriteLine( _numbers.Sum());// sum: 100```

Sum method with Query Syntax
this is an example of LINQ query expression to get sum of any collection

```var numberList = new List<int> { 10, 55, 5, 19, 9, 2};
int total = (from x in numberList select x).Sum();
Console.WriteLine(total); // sum: 100```

### LINQ Sum with Group By Example

In this example we learn how to use Sum with GroupBy to find out the score of each stream.

```var studentsStream = new List<Student> { new Student { FullName = "Aruna", StreamId=1, Score = 10 },
new Student { FullName = "Janet", StreamId=2, Score = 9 },
new Student { FullName = "Ajay", StreamId=1, Score = 11 },
new Student { FullName = "Kunal", StreamId=2, Score = 13 },
new Student { FullName = "Chandra", StreamId=2, Score = 8 },
};
var groupScores =
from techStream in studentsStream
group techStream by techStream.StreamId into studentGroup
select new
{
Stream = studentGroup.Key,
GroupScore = studentGroup.Sum(x => x.Score),
};

foreach (var scr in groupScores)
{
Console.WriteLine(string.Format("{0}-{1}", scr.Stream, scr.GroupScore));
}```

In above code we have calculated the Sum scrore of each stream, here is the result

```1 - 21
2 - 30```
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LINQ Sum method Example in C#

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