ObjectQuery<T>.Distinct 方法

public:
 System::Data::Objects::ObjectQuery<T> ^ Distinct();

public System.Data.Objects.ObjectQuery<T> Distinct();

member this.Distinct : unit -> System.Data.Objects.ObjectQuery<'T>

Public Function Distinct () As ObjectQuery(Of T)

返回

与应用 SELECT DISTINCT 的原始实例等效的新ObjectQuery<T>实例。

示例

此示例使用 UnionAll 方法创建新 ObjectQuery<T> 对象。 然后，它调用 Distinct 新 ObjectQuery<T> 对象以获取此查询的唯一结果。

int productID = 100;
using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    string queryString =
        @"SELECT VALUE product FROM AdventureWorksEntities.Products
            AS product WHERE product.ProductID < @productID";

    ObjectQuery<Product> productQuery =
        new ObjectQuery<Product>(queryString,
            context, MergeOption.NoTracking);

    ObjectQuery<Product> productQuery2 =
        new ObjectQuery<Product>(queryString,
            context, MergeOption.NoTracking);

    ObjectQuery<Product> productQuery3 =
        productQuery.UnionAll(productQuery2);

    productQuery3.Parameters.Add(new ObjectParameter("productID", productID));

    Console.WriteLine("Result of UnionAll");
    Console.WriteLine("------------------");

    // Iterate through the collection of Product items,
    // after the UnionAll method was called on two queries.
    foreach (Product result in productQuery3)
    {
        Console.WriteLine("Product Name: {0}", result.ProductID);
    }
    ObjectQuery<Product> productQuery4 = productQuery3.Distinct();

    Console.WriteLine("\nResult of Distinct");
    Console.WriteLine("------------------");

    // Iterate through the collection of Product items.
    // after the Distinct method was called on a query.
    foreach (Product result in productQuery4)
        Console.WriteLine("Product Name: {0}", result.ProductID);
}

注解

此查询生成器方法返回一个 ObjectQuery<T> 实例，该实例等效于应用 SELECT DISTINCT 的原始查询。

DISTINCT该运算符不能应用于包含数据源中非可比列的映射的对象（如 ntext）。

另请参阅

• 将数据查询为对象（实体框架）