방법: 데이터 서비스 쿼리에 쿼리 옵션 추가(WCF Data Services)

WCF Data Services를 사용하면 생성된 클라이언트 데이터 서비스 클래스를 통해 .NET Framework 기반 클라이언트 응용 프로그램에서 데이터 서비스를 쿼리할 수 있습니다. 이렇게 하는 가장 쉬운 방법은 원하는 쿼리 옵션이 포함된 LINQ(Language Integrated Query) 쿼리 식을 작성하는 것입니다. 일련의 LINQ 쿼리 메서드를 호출하여 동등한 쿼리를 작성할 수도 있습니다. 마지막으로 AddQueryOption 메서드를 사용하여 쿼리에 쿼리 옵션을 추가할 수 있습니다. 이러한 각 경우에 클라이언트에서 생성된 URI에는 선택한 쿼리 옵션이 적용된 요청한 엔터티 집합이 포함됩니다. 자세한 내용은 데이터 서비스 쿼리(WCF Data Services)를 참조하십시오.

이 항목의 예제에서는 Northwind 샘플 데이터 서비스 및 자동 생성된 클라이언트 데이터 서비스 클래스를 사용합니다. 이 서비스 및 클라이언트 데이터 클래스는 WCF Data Services 퀵 스타트를 완료하면 만들어집니다.

예

다음 예제에서는 운송료가 $30를 초과하는 주문만 반환하고 운송 날짜의 내림차순으로 결과를 정렬하는 LINQ 쿼리 식을 작성하는 방법을 보여 줍니다.

' Create the DataServiceContext using the service URI.
Dim context = New NorthwindEntities(svcUri)

' Define a query for orders with a Freight value greater than 30
' and that is ordered by the ship date, descending.
Dim selectedOrders = From o In context.Orders _
        Where (o.Freight > 30) _
        Order By o.ShippedDate Descending _
        Select o

Try
    ' Enumerate over the results of the query.
    For Each order As Order In selectedOrders
        Console.WriteLine("Order ID: {0} - Ship Date: {1} - Freight: {2}", _
                order.OrderID, order.ShippedDate, order.Freight)
    Next
Catch ex As DataServiceQueryException
    Throw New ApplicationException( _
            "An error occurred during query execution.", ex)
End Try

// Create the DataServiceContext using the service URI.
NorthwindEntities context = new NorthwindEntities(svcUri);

// Define a query for orders with a Freight value greater than 30
// and that is ordered by the ship date, descending.
var selectedOrders = from o in context.Orders
                     where o.Freight > 30
                     orderby o.ShippedDate descending 
                     select o;

try
{
    // Enumerate over the results of the query.
    foreach (Order order in selectedOrders)
    {
        Console.WriteLine("Order ID: {0} - Ship Date: {1} - Freight: {2}",
            order.OrderID, order.ShippedDate, order.Freight);
    }
}
catch (DataServiceQueryException ex)
{
    throw new ApplicationException(
        "An error occurred during query execution.", ex);
}

다음 예제에서는 LINQ 쿼리 메서드를 사용하여 앞의 쿼리와 동등한 LINQ 쿼리를 작성하는 방법을 보여 줍니다.

' Create the DataServiceContext using the service URI.
Dim context = New NorthwindEntities(svcUri)

' Define a query for orders with a Freight value greater than 30
' and that is ordered by the ship date, descending.
Dim selectedOrders = context.Orders _
                     .Where(Function(o) o.Freight.Value > 30) _
                     .OrderByDescending(Function(o) o.ShippedDate)

Try
    ' Enumerate over the results of the query.
    For Each order As Order In selectedOrders

        Console.WriteLine("Order ID: {0} - Ship Date: {1} - Freight: {2}", _
                order.OrderID, order.ShippedDate, order.Freight)
    Next
Catch ex As DataServiceQueryException
    Throw New ApplicationException( _
        "An error occurred during query execution.", ex)
End Try

// Create the DataServiceContext using the service URI.
NorthwindEntities context = new NorthwindEntities(svcUri);

// Define a query for orders with a Freight value greater than 30
// and that is ordered by the ship date, descending.
var selectedOrders = context.Orders
                    .Where(o => o.Freight > 30)
                    .OrderByDescending(o => o.ShippedDate);

try
{
    // Enumerate over the results of the query.
    foreach (Order currentOrder in selectedOrders)
    {
        Console.WriteLine("Order ID: {0} - Ship Date: {1} - Freight: {2}",
            currentOrder.OrderID, currentOrder.ShippedDate, 
            currentOrder.Freight);
    }
}
catch (DataServiceQueryException ex)
{
    throw new ApplicationException(
        "An error occurred during query execution.", ex);
}

다음 예제에서는 AddQueryOption 메서드를 사용하여 앞의 예제와 동등한 DataServiceQuery<TElement>를 만드는 방법을 보여 줍니다.

' Create the DataServiceContext using the service URI.
Dim context = New NorthwindEntities(svcUri)

' Define a query for orders with a Freight value greater than 30
' and that is ordered by the ship date, descending.
Dim selectedOrders As DataServiceQuery(Of Order) = context.Orders _
.AddQueryOption("$filter", "Freight gt 30") _
.AddQueryOption("$orderby", "OrderID desc")

Try
    ' Enumerate over the results of the query.
    For Each order As Order In selectedOrders
        Console.WriteLine("Order ID: {0} - Ship Date: {1} - Freight: {2}", _
                order.OrderID, order.ShippedDate, order.Freight)
    Next
Catch ex As DataServiceQueryException
    Throw New ApplicationException( _
            "An error occurred during query execution.", ex)
End Try

// Create the DataServiceContext using the service URI.
NorthwindEntities context = new NorthwindEntities(svcUri);

// Define a query for orders with a Freight value greater than 30
// and that is ordered by the ship date, descending.
DataServiceQuery<Order> selectedOrders = context.Orders
    .AddQueryOption("$filter", "Freight gt 30")
    .AddQueryOption("$orderby", "OrderID desc");

try
{
    // Enumerate over the results of the query.
    foreach (Order order in selectedOrders)
    {
        Console.WriteLine("Order ID: {0} - Ship Date: {1} - Freight: {2}", 
            order.OrderID, order.ShippedDate, order.Freight);
    }
}
catch (DataServiceQueryException ex)
{
    throw new ApplicationException(
        "An error occurred during query execution.", ex);
}

다음 예제에서는 $orderby 쿼리 옵션을 사용하여 Freight 속성을 기준으로 반환된 Orders 개체를 필터링 및 정렬하는 방법을 보여 줍니다.

' Create the DataServiceContext using the service URI.
Dim context = New NorthwindEntities(svcUri)

' Define a query for orders with a Freight value greater than 30
' that also orders the result by the Freight value, descending.
Dim selectedOrders As DataServiceQuery(Of Order) = _
context.Orders.AddQueryOption("$orderby", "Freight gt 30 desc")

Try
    ' Enumerate over the results of the query.
    For Each order As Order In selectedOrders
        Console.WriteLine("Order ID: {0} - Freight: {1}", _
                order.OrderID, order.Freight)
    Next
Catch ex As DataServiceQueryException
    Throw New ApplicationException( _
            "An error occurred during query execution.", ex)
End Try

// Create the DataServiceContext using the service URI.
NorthwindEntities context = new NorthwindEntities(svcUri);

// Define a query for orders with a Freight value greater than 30
// that also orders the result by the Freight value, descending.
DataServiceQuery<Order> selectedOrders = context.Orders
    .AddQueryOption("$orderby", "Freight gt 30 desc");

try
{
    // Enumerate over the results of the query.
    foreach (Order order in selectedOrders)
    {
        Console.WriteLine("Order ID: {0} - Freight: {1}",
            order.OrderID, order.Freight);
    }
}
catch (DataServiceQueryException ex)
{
    throw new ApplicationException(
        "An error occurred during query execution.", ex);
}

참고 항목

태스크

방법: 쿼리 결과 프로젝션(WCF Data Services)

개념

데이터 서비스 쿼리(WCF Data Services)