Enumerable.Except(TSource) Method (IEnumerable(TSource), IEnumerable(TSource))
Produces the set difference of two sequences by using the default equality comparer to compare values.
Assembly: System.Core (in System.Core.dll)
static member Except : first:IEnumerable<'TSource> * second:IEnumerable<'TSource> -> IEnumerable<'TSource>
The type of the elements of the input sequences.
- Type: System.Collections.Generic.IEnumerable()
An IEnumerable(T) whose elements that are not also in second will be returned.
Return ValueType: System.Collections.Generic.IEnumerable()
A sequence that contains the set difference of the elements of two sequences.
Usage NoteIn Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable(). When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).
first or second is a null reference (Nothing in Visual Basic).
This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.
The set difference of two sets is defined as the members of the first set that do not appear in the second set.
This method returns those elements in first that do not appear in second. It does not also return those elements in second that do not appear in first.
To compare custom data types, implement the IEquatable(T) generic interface and provide your own GetHashCode and Equals methods for the type. The default equality comparer, Default, is used to compare values of types that implement IEquatable(T).
The following code example demonstrates how to use the method to compare two sequences of numbers and return elements that appear only in the first sequence.
If you want to compare sequences of objects of some custom data type, implement the IEquatable(T) generic interface in your class. The following code example shows how to implement this interface in a custom data type, Product, and to provide GetHashCode and Equals methods.
After you implement this interface, you can use sequences of Product objects to call the method, as shown in the following example.
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.