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已編譯的查詢 (LINQ to Entities)

當您的應用程式執行了 Entity Framework 中結構類似的查詢多次時,您可經常增加效能,其方式是編譯查詢一次,然後使用不同的參數執行查詢多次。 例如,應用程式可能必須擷取特定城市中的所有客戶;此城市是使用者在執行階段於表單中所指定。 LINQ to Entities 支援針對這個用途所編譯的查詢。

CompiledQuery 類別提供查詢的編譯和快取以供重複使用。 就概念而言,這個類別包含數個多載之 CompiledQueryCompile 方法。 呼叫 Compile 方法可建立新委派來代表已編譯的查詢。 ObjectContext 所提供的 Compile 方法和參數值會傳回一個產生某個結果 (例如 IQueryable 執行個體) 的委派。 此查詢只會在第一次執行期間編譯一次。 不過,您之後無法變更在編譯階段中,針對查詢所設定的合併選項。 一旦查詢已編譯之後,您就只能提供基本型別的參數,但是無法取代會變更產生之 SQL 的查詢部分。 如需詳細資訊,請參閱 Entity Framework 合併選項和編譯的查詢 (英文)。

CompiledQueryCompile 方法所編譯的 LINQ to Entities 查詢運算式是由其中一個泛型 Func 委派代表,例如 Func。 查詢運算式最多只能封裝一個 ObjectContext 參數、一個傳回參數和十六個查詢參數。 如果需要使用十六個以上的查詢參數,您可以建立其屬性代表查詢參數的結構。 然後,當您設定這些參數之後,就可以將此結構的屬性用於查詢運算式中。

範例

下列範例會先編譯然後再叫用接受 Decimal 輸入參數的查詢,並且傳回訂單序列,其中的總到期金額大於或等於 $200.00:

ReadOnly s_compQuery2 As Func(Of AdventureWorksEntities, Decimal, IQueryable(Of SalesOrderHeader)) = _
    CompiledQuery.Compile(Of AdventureWorksEntities, Decimal, IQueryable(Of SalesOrderHeader))( _
                Function(ctx As AdventureWorksEntities, total As Decimal) _
                    From order In ctx.SalesOrderHeaders _
                    Where (order.TotalDue >= total) _
                    Select order)

Sub CompiledQuery2()
    Using context As New AdventureWorksEntities()

        Dim totalDue As Decimal = 200.0

        Dim orders As IQueryable(Of SalesOrderHeader) = s_compQuery2.Invoke(context, totalDue)

        For Each order In orders
            Console.WriteLine("ID: {0}  Order date: {1} Total due: {2}", _
                                    order.SalesOrderID, _
                                    order.OrderDate, _
                                    order.TotalDue)
        Next
    End Using
End Sub
static readonly Func<AdventureWorksEntities, Decimal, IQueryable<SalesOrderHeader>> s_compiledQuery2 = 
    CompiledQuery.Compile<AdventureWorksEntities, Decimal, IQueryable<SalesOrderHeader>>(
            (ctx, total) => from order in ctx.SalesOrderHeaders
                            where order.TotalDue >= total
                            select order);

static void CompiledQuery2()
{            
    using (AdventureWorksEntities context = new AdventureWorksEntities())
    {
        Decimal totalDue = 200.00M;

        IQueryable<SalesOrderHeader> orders = s_compiledQuery2.Invoke(context, totalDue);

        foreach (SalesOrderHeader order in orders)
        {
            Console.WriteLine("ID: {0}  Order date: {1} Total due: {2}",
                order.SalesOrderID,
                order.OrderDate,
                order.TotalDue);
        }
    }            
}

範例

下列範例會先編譯再叫用傳回 ObjectQuery 執行個體的查詢:

ReadOnly s_compQuery1 As Func(Of AdventureWorksEntities, ObjectQuery(Of SalesOrderHeader)) = _
    CompiledQuery.Compile(Of AdventureWorksEntities, ObjectQuery(Of SalesOrderHeader))( _
                Function(ctx) ctx.SalesOrderHeaders)

Sub CompiledQuery1_MQ()

    Using context As New AdventureWorksEntities()

        Dim orders As ObjectQuery(Of SalesOrderHeader) = s_compQuery1.Invoke(context)

        For Each order In orders
            Console.WriteLine(order.SalesOrderID)
        Next

    End Using
End Sub
static readonly Func<AdventureWorksEntities, ObjectQuery<SalesOrderHeader>> s_compiledQuery1 = 
    CompiledQuery.Compile<AdventureWorksEntities, ObjectQuery<SalesOrderHeader>>(
            ctx => ctx.SalesOrderHeaders);

static void CompiledQuery1_MQ()
{
    
    using (AdventureWorksEntities context = new AdventureWorksEntities())
    {
        IQueryable<SalesOrderHeader> orders = s_compiledQuery1.Invoke(context);

        foreach (SalesOrderHeader order in orders)
            Console.WriteLine(order.SalesOrderID);
    }            
}

範例

下列範例會先編譯再叫用一個查詢,此查詢會以 Decimal 值形式傳回產品標價的平均值。

Using context As New AdventureWorksEntities()
    Dim compQuery = CompiledQuery.Compile(Of AdventureWorksEntities, Decimal)( _
            Function(ctx) ctx.Products.Average(Function(Product) Product.ListPrice))

    Dim averageProductPrice As Decimal = compQuery.Invoke(context)

    Console.WriteLine("The average of the product list prices is $: {0}", averageProductPrice)
End Using
static readonly Func<AdventureWorksEntities, Decimal> s_compiledQuery3MQ = CompiledQuery.Compile<AdventureWorksEntities, Decimal>(
            ctx => ctx.Products.Average(product => product.ListPrice));

static void CompiledQuery3_MQ()
{
    
    using (AdventureWorksEntities context = new AdventureWorksEntities())
    {
        Decimal averageProductPrice = s_compiledQuery3MQ.Invoke(context);

        Console.WriteLine("The average of the product list prices is $: {0}", averageProductPrice);
    }            
}

範例

下列範例會先編譯然後再叫用接受 String 輸入參數的查詢,然後傳回電子郵件地址以指定字串開始的 Contact

Using context As New AdventureWorksEntities()
    Dim compQuery = CompiledQuery.Compile(Of AdventureWorksEntities, String, Contact)( _
            Function(ctx, name) ctx.Contacts.First(Function(contact) contact.EmailAddress.StartsWith(name)))

    Dim contactName As String = "caroline"
    Dim foundContact As Contact = compQuery.Invoke(context, contactName)

    Console.WriteLine("An email address starting with 'caroline': {0}", _
            foundContact.EmailAddress)
End Using
static readonly Func<AdventureWorksEntities, string, Contact> s_compiledQuery4MQ = 
    CompiledQuery.Compile<AdventureWorksEntities, string, Contact>(
            (ctx, name) => ctx.Contacts.First(contact => contact.EmailAddress.StartsWith(name)));

static void CompiledQuery4_MQ()
{            
    using (AdventureWorksEntities context = new AdventureWorksEntities())
    {
        string contactName = "caroline";
        Contact foundContact = s_compiledQuery4MQ.Invoke(context, contactName);

        Console.WriteLine("An email address starting with 'caroline': {0}",
            foundContact.EmailAddress);
    }            
}

範例

下列範例會先編譯然後再叫用接受 DateTimeDecimal 輸入參數的查詢,並且傳回訂單序列,其中的訂單日期晚於 2003 年 3 月 8 日,總應付金額則少於 $300.00:

ReadOnly s_compQuery5 = _
   CompiledQuery.Compile(Of AdventureWorksEntities, DateTime, Decimal, IQueryable(Of SalesOrderHeader))( _
                Function(ctx, orderDate, totalDue) From product In ctx.SalesOrderHeaders _
                                                   Where product.OrderDate > orderDate _
                                                      And product.TotalDue < totalDue _
                                                   Order By product.OrderDate _
                                                   Select product)
Sub CompiledQuery5()

    Using context As New AdventureWorksEntities()

        Dim orderedAfterDate As DateTime = New DateTime(2003, 3, 8)
        Dim amountDue As Decimal = 300.0

        Dim orders As IQueryable(Of SalesOrderHeader) = _
            s_compQuery5.Invoke(context, orderedAfterDate, amountDue)

        For Each order In orders
            Console.WriteLine("ID: {0} Order date: {1} Total due: {2}", _
                              order.SalesOrderID, order.OrderDate, order.TotalDue)
        Next

    End Using
End Sub
static readonly Func<AdventureWorksEntities, DateTime, Decimal, IQueryable<SalesOrderHeader>> s_compiledQuery5 = 
    CompiledQuery.Compile<AdventureWorksEntities, DateTime, Decimal, IQueryable<SalesOrderHeader>>(
            (ctx, orderDate, totalDue) => from product in ctx.SalesOrderHeaders
                                          where product.OrderDate > orderDate 
                                             && product.TotalDue < totalDue
                                          orderby product.OrderDate
                                          select product);

static void CompiledQuery5()
{            
    using (AdventureWorksEntities context = new AdventureWorksEntities())
    {         
        DateTime date = new DateTime(2003, 3, 8);
        Decimal amountDue = 300.00M;

        IQueryable<SalesOrderHeader> orders = s_compiledQuery5.Invoke(context, date, amountDue);

        foreach (SalesOrderHeader order in orders)
        {
            Console.WriteLine("ID: {0} Order date: {1} Total due: {2}", order.SalesOrderID, order.OrderDate, order.TotalDue);
        }
    }            
}

範例

下列範例會先編譯然後再叫用接受 DateTime 輸入參數的查詢,並且傳回訂單序列,其中的訂單日期晚於 2004 年 3 月 8 日。 此查詢會傳回匿名型別序列形式的訂單資訊。 匿名型別是由編譯器所推斷,所以您無法在 CompiledQueryCompile 方法中指定型別參數,而且此型別會在查詢本身定義。

Using context As New AdventureWorksEntities()
    Dim compQuery = CompiledQuery.Compile( _
            Function(ctx As AdventureWorksEntities, orderDate As DateTime) _
                From order In ctx.SalesOrderHeaders _
                Where order.OrderDate > orderDate _
                Select New With {order.OrderDate, order.SalesOrderID, order.TotalDue})

    Dim orderedAfterDate As DateTime = New DateTime(2004, 3, 8)

    Dim orders = compQuery.Invoke(context, orderedAfterDate)

    For Each order In orders
        Console.WriteLine("ID: {0} Order date: {1} Total due: {2}", _
                          order.SalesOrderID, order.OrderDate, order.TotalDue)
    Next

End Using
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
    var compiledQuery = CompiledQuery.Compile((AdventureWorksEntities ctx, DateTime orderDate) =>
        from order in ctx.SalesOrderHeaders
        where order.OrderDate > orderDate
        select new {order.OrderDate, order.SalesOrderID, order.TotalDue});

    DateTime date = new DateTime(2004, 3, 8);
    var results = compiledQuery.Invoke(context, date);

    foreach (var order in results)
    {
        Console.WriteLine("ID: {0} Order date: {1} Total due: {2}", order.SalesOrderID, order.OrderDate, order.TotalDue);
    }
}

範例

下列範例會先編譯然後再叫用接受使用者定義結構輸入參數的查詢,並傳回訂單序列。 此結構會定義開始日期、結束日期和應付總額查詢參數,而且此查詢會傳回在 2003 年 3 月 3 日與 3 月 8 日之間出貨而且應付總額超過 $700.00 的訂單。

ReadOnly s_compQuery = CompiledQuery.Compile(Of AdventureWorksEntities, MyParams, IQueryable(Of SalesOrderHeader))( _
                Function(ctx, mySearchParams) _
                    From sale In ctx.SalesOrderHeaders _
                    Where sale.ShipDate > mySearchParams.startDate _
                       And sale.ShipDate < mySearchParams.endDate _
                       And sale.TotalDue > mySearchParams.totalDue _
                    Select sale)

Sub CompiledQuery7()

    Using context As New AdventureWorksEntities()

        Dim myParams As MyParams = New MyParams()
        myParams.startDate = New DateTime(2003, 3, 3)
        myParams.endDate = New DateTime(2003, 3, 8)
        myParams.totalDue = 700.0

        Dim sales = s_compQuery.Invoke(context, myParams)

        For Each sale In sales
            Console.WriteLine("ID: {0}", sale.SalesOrderID)
            Console.WriteLine("Ship date: {0}", sale.ShipDate)
            Console.WriteLine("Total due: {0}", sale.TotalDue)
        Next

    End Using
End Sub
static Func<AdventureWorksEntities, MyParams, IQueryable<SalesOrderHeader>> s_compiledQuery = 
    CompiledQuery.Compile<AdventureWorksEntities, MyParams, IQueryable<SalesOrderHeader>>(
            (ctx, myparams) => from sale in ctx.SalesOrderHeaders
                               where sale.ShipDate > myparams.startDate && sale.ShipDate < myparams.endDate 
                               && sale.TotalDue > myparams.totalDue  
                               select sale);
static void CompiledQuery7()
{
    
    using (AdventureWorksEntities context = new AdventureWorksEntities())
    {
        MyParams myParams = new MyParams();
        myParams.startDate = new DateTime(2003, 3, 3);
        myParams.endDate = new DateTime(2003, 3, 8);
        myParams.totalDue = 700.00M;

        

        IQueryable<SalesOrderHeader> sales = s_compiledQuery.Invoke(context, myParams);

        foreach (SalesOrderHeader sale in sales)
        {
            Console.WriteLine("ID: {0}", sale.SalesOrderID);
            Console.WriteLine("Ship date: {0}", sale.ShipDate);
            Console.WriteLine("Total due: {0}", sale.TotalDue);
        }
    }            
}

定義查詢參數的結構:

Public Structure MyParams
    Public startDate As DateTime
    Public endDate As DateTime
    Public totalDue As Decimal
End Structure
struct MyParams
{
    public DateTime startDate;
    public DateTime endDate;
    public decimal totalDue;
}

另請參閱

概念

ADO.NET Entity Framework
LINQ to Entities

其他資源

Entity Framework 合併選項和編譯的查詢