ObjectQuery<T>.Top(String, ObjectParameter[]) 方法

public:
 System::Data::Objects::ObjectQuery<T> ^ Top(System::String ^ count, ... cli::array <System::Data::Objects::ObjectParameter ^> ^ parameters);

public System.Data.Objects.ObjectQuery<T> Top(string count, params System.Data.Objects.ObjectParameter[] parameters);

member this.Top : string * System.Data.Objects.ObjectParameter[] -> System.Data.Objects.ObjectQuery<'T>

Public Function Top (count As String, ParamArray parameters As ObjectParameter()) As ObjectQuery(Of T)

参数

返回

与应用 TOP 的原始实例等效的新ObjectQuery<T>实例。

例外

示例

此示例创建一个包含现有查询的前两个 ObjectQuery<T> 结果的新项。

using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    string queryString =
        @"SELECT VALUE product FROM AdventureWorksEntities.Products AS product";

    ObjectQuery<Product> productQuery1 =
        new ObjectQuery<Product>(queryString, context, MergeOption.NoTracking);

    ObjectQuery<Product> productQuery2 = productQuery1.Top("2");

    // Iterate through the collection of Product items.
    foreach (Product result in productQuery2)
        Console.WriteLine("{0}", result.Name);
}

本示例在跳过查询结果中的前三个对象后获取五 Product 个对象，排序依据 Product.ListPrice。 Top 用于分页，而不是 LIMIT 。

using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    // Define the parameters used to define the "page" of returned data.
    int skipValue = 3;
    int limitValue = 5;

    // Define a query that returns a "page" or the full
    // Product data using the Skip and Top methods.
    // When Top() follows Skip(), it acts like the LIMIT statement.
    ObjectQuery<Product> query = context.Products
        .Skip("it.ListPrice", "@skip",
                new ObjectParameter("skip", skipValue))
        .Top("@limit", new ObjectParameter("limit", limitValue));

    // Iterate through the page of Product items.
    foreach (Product result in query)
        Console.WriteLine("ID: {0}; Name: {1}",
        result.ProductID, result.Name);
}

注解

Top 是不确定的，除非对查询进行排序。

在方法之后Skip使用Top该方法时，该方法的工作方式类似于 ORDER BY 子句的 LIMIT 语句。

另请参阅

• 将数据查询为对象（实体框架）