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

Computes the sum of the sequence of nullable 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 Nullable<int> Sum<TSource>(
	this IEnumerable<TSource> source,
	Func<TSource, Nullable<int>> selector
)

Type Parameters

TSource

The type of the elements of source.

Parameters

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

Return Value

Type: System.Nullable<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.

ExceptionCondition
ArgumentNullException

source or selector is null.

OverflowException

The sum is larger than MaxValue.

This method returns zero if source contains no elements.

The result does not include values that are null.

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 Nullable<Int32> in C# or Nullable(Of Int32) in Visual Basic.

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

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

NoteNote:

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
      */



Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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