Enumerable.SequenceEqual<TSource> Method (IEnumerable<TSource>, IEnumerable<TSource>)

Determines whether two sequences are equal by comparing the elements by using the default equality comparer for their type.

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

public static bool SequenceEqual<TSource>(
	this IEnumerable<TSource> first,
	IEnumerable<TSource> second
)

Type Parameters

TSource

The type of the elements of the input sequences.

Parameters

first
Type: System.Collections.Generic.IEnumerable<TSource>
An IEnumerable<T> to compare to second.
second
Type: System.Collections.Generic.IEnumerable<TSource>
An IEnumerable<T> to compare to the first sequence.

Return Value

Type: System.Boolean
true if the two source sequences are of equal length and their corresponding elements are equal according to the default equality comparer for their type; otherwise, false.

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

first or second is null.

The SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) method enumerates the two source sequences in parallel and compares corresponding elements by using the default equality comparer for TSource, Default. The default equality comparer, Default, is used to compare values of the types that implement the IEqualityComparer<T> generic interface. To compare a custom data type, you need to implement this interface and provide your own GetHashCode and Equals methods for the type.

The following code examples demonstrate how to use SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) to determine whether two sequences are equal. In the first two examples, the method determines whether the compared sequences contain references to the same objects. In the third and fourth examples, the method compares the actual data of the objects within the sequences.

In this example the sequences are equal.


      class Pet
      {
         public string Name { get; set; }
         public int Age { get; set; }
      }

      public static void SequenceEqualEx1()
      {
         Pet pet1 = new Pet { Name = "Turbo", Age = 2 };
         Pet pet2 = new Pet { Name = "Peanut", Age = 8 };

         // Create two lists of pets.
         List<Pet> pets1 = new List<Pet> { pet1, pet2 };
         List<Pet> pets2 = new List<Pet> { pet1, pet2 };

         bool equal = pets1.SequenceEqual(pets2);

         outputBlock.Text += String.Format(
             "The lists {0} equal.",
             equal ? "are" : "are not") + "\n";
      }

      /*
       This code produces the following output:

       The lists are equal.
      */



The following code example compares two sequences that are not equal. Note that the sequences contain identical data, but because the objects that they contain have different references, the sequences are not considered equal.


      class Pet
      {
         public string Name { get; set; }
         public int Age { get; set; }
      }

      public static void SequenceEqualEx2()
      {
         Pet pet1 = new Pet() { Name = "Turbo", Age = 2 };
         Pet pet2 = new Pet() { Name = "Peanut", Age = 8 };

         // Create two lists of pets.
         List<Pet> pets1 = new List<Pet> { pet1, pet2 };
         List<Pet> pets2 =
             new List<Pet> { new Pet { Name = "Turbo", Age = 2 }, 
                                 new Pet { Name = "Peanut", Age = 8 } };

         bool equal = pets1.SequenceEqual(pets2);

         outputBlock.Text += String.Format("The lists {0} equal.", equal ? "are" : "are not") + "\n";
      }

      /*
       This code produces the following output:

       The lists are not equal.
      */



If you want to compare the actual data of the objects in the sequences instead of just comparing their references, you have to implement the IEqualityComparer<T> generic interface in your class.

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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