Sum(TSource) Method (IEnumerable(TSource), Func(TSource, Int32))

Enumerable.Sum<TSource> Method (IEnumerable<TSource>, Func<TSource, Int32>)

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Computes the sum of the sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence.

Namespace:  System.Linq
Assembly:  System.Core (in System.Core.dll)

public static int Sum<TSource>(
	this IEnumerable<TSource> source,
	Func<TSource, int> selector

Type Parameters


The type of the elements of source.


Type: System.Collections.Generic.IEnumerable<TSource>
A sequence of values that are used to calculate a sum.
Type: System.Func<TSource, Int32>
A transform function to apply to each element.

Return Value

Type: System.Int32
The sum of the projected values.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable<TSource>. When you use instance method syntax to call this method, omit the first parameter.


source or selector is null.


The sum is larger than MaxValue.

This method returns zero if source contains no elements.

You can apply this method to a sequence of arbitrary values if you provide a function, selector, that projects the members of source into a numeric type, specifically Int32.

In Visual Basic query expression syntax, an Aggregate Into Sum() clause translates to an invocation of Enumerable.Sum.

The following code example demonstrates how to use Sum<TSource>(IEnumerable<TSource>, Func<TSource, Double>) to sum the projected values of a sequence.


This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. To extend the example to this topic, change the body of the selector function.

      class Package
         public string Company { get; set; }
         public double Weight { get; set; }

      public static void SumEx1()
         List<Package> packages =
             new List<Package> 
                     { new Package { Company = "Coho Vineyard", Weight = 25.2 },
                       new Package { Company = "Lucerne Publishing", Weight = 18.7 },
                       new Package { Company = "Wingtip Toys", Weight = 6.0 },
                       new Package { Company = "Adventure Works", Weight = 33.8 } };

         double totalWeight = packages.Sum(pkg => pkg.Weight);

         outputBlock.Text += String.Format("The total weight of the packages is: {0}", totalWeight) + "\n";

       This code produces the following output:

       The total weight of the packages is: 83.7

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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