Enumerable.SequenceEqual<TSource> Method (IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)
Determines whether two sequences are equal by comparing their elements by using a specified IEqualityComparer<T>.
Namespace: System.Linq
Assembly: System.Core (in System.Core.dll)
public static bool SequenceEqual<TSource>( this IEnumerable<TSource> first, IEnumerable<TSource> second, IEqualityComparer<TSource> comparer )
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.
- comparer
- Type: System.Collections.Generic.IEqualityComparer<TSource>
An IEqualityComparer<T> to use to compare elements.
Return Value
Type: System.Booleantrue if the two source sequences are of equal length and their corresponding elements compare equal according to comparer; 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).| Exception | Condition |
|---|---|
| ArgumentNullException | first or second is null. |
The SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>) method enumerates the two source sequences in parallel and compares corresponding elements by using the specified IEqualityComparer<T>. If comparer is null, the default equality comparer, Default, is used to compare elements.
The following example shows how to implement an equality comparer that can be used in the SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>) method.
public class Product { public string Name { get; set; } public int Code { get; set; } } // Custom comparer for the Product class class ProductComparer : IEqualityComparer<Product> { // Products are equal if their names and product numbers are equal. public bool Equals(Product x, Product y) { //Check whether the compared objects reference the same data. if (Object.ReferenceEquals(x, y)) return true; //Check whether any of the compared objects is null. if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null)) return false; //Check whether the products' properties are equal. return x.Code == y.Code && x.Name == y.Name; } // If Equals() returns true for a pair of objects // then GetHashCode() must return the same value for these objects. public int GetHashCode(Product product) { //Check whether the object is null if (Object.ReferenceEquals(product, null)) return 0; //Get hash code for the Name field if it is not null. int hashProductName = product.Name == null ? 0 : product.Name.GetHashCode(); //Get hash code for the Code field. int hashProductCode = product.Code.GetHashCode(); //Calculate the hash code for the product. return hashProductName ^ hashProductCode; } }
After you implement this comparer, you can use sequences of Product objects in the SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<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, new ProductComparer());
Console.WriteLine("Equal? " + equalAB);
/*
This code produces the following output:
Equal? True
*/
Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.