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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. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).

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);

                Console.WriteLine(
                    "The lists {0} equal.",
                    equal ? "are" : "are not");
            }

            /*
             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);

                Console.WriteLine("The lists {0} equal.", equal ? "are" : "are not");
            }

            /*
             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. The following code example shows how to implement this interface in a custom data type and provide GetHashCode and Equals methods.


public class Product : IEquatable<Product>
{
    public string Name { get; set; }
    public int Code { get; set; }

    public bool Equals(Product other)
    {

        //Check whether the compared object is null.
        if (Object.ReferenceEquals(other, null)) return false;

        //Check whether the compared object references the same data.
        if (Object.ReferenceEquals(this, other)) return true;

        //Check whether the products' properties are equal.
        return Code.Equals(other.Code) && Name.Equals(other.Name);
    }

    // If Equals() returns true for a pair of objects 
    // then GetHashCode() must return the same value for these objects.

    public override int GetHashCode()
    {

        //Get hash code for the Name field if it is not null.
        int hashProductName = Name == null ? 0 : Name.GetHashCode();

        //Get hash code for the Code field.
        int hashProductCode = Code.GetHashCode();

        //Calculate the hash code for the product.
        return hashProductName ^ hashProductCode;
    }
}


After you implement this interface, you can use sequences of Product objects in the SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) method, as shown in the following example.



        Product[] storeA = { new Product { Name = "apple", Code = 9 }, 
                               new Product { Name = "orange", Code = 4 } };

        Product[] storeB = { new Product { Name = "apple", Code = 9 }, 
                               new Product { Name = "orange", Code = 4 } };

        bool equalAB = storeA.SequenceEqual(storeB);

        Console.WriteLine("Equal? " + equalAB);

        /*
            This code produces the following output:

            Equal? True
        */



.NET Framework

Supported in: 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

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.

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