ObjectQuery<T>.GroupBy(String, String, ObjectParameter[]) Metoda

Definicja

Grupuje wyniki zapytania według określonych kryteriów.Groups the query results by the specified criteria.

public:
 System::Data::Objects::ObjectQuery<System::Data::Common::DbDataRecord ^> ^ GroupBy(System::String ^ keys, System::String ^ projection, ... cli::array <System::Data::Objects::ObjectParameter ^> ^ parameters);
public System.Data.Objects.ObjectQuery<System.Data.Common.DbDataRecord> GroupBy (string keys, string projection, params System.Data.Objects.ObjectParameter[] parameters);
member this.GroupBy : string * string * System.Data.Objects.ObjectParameter[] -> System.Data.Objects.ObjectQuery<System.Data.Common.DbDataRecord>
Public Function GroupBy (keys As String, projection As String, ParamArray parameters As ObjectParameter()) As ObjectQuery(Of DbDataRecord)

Parametry

keys
String

Kolumny klucza, według których mają być grupowane wyniki.The key columns by which to group the results.

projection
String

Lista wybranych właściwości, które definiują projekcję.The list of selected properties that defines the projection.

parameters
ObjectParameter[]

Zero lub więcej parametrów, które są używane w tej metodzie.Zero or more parameters that are used in this method.

Zwraca

Nowe wystąpienie ObjectQuery<T> typu DbDataRecord, które jest równoważne z oryginalnym wystąpieniem z zastosowaniem grupy .A new ObjectQuery<T> instance of type DbDataRecord that is equivalent to the original instance with GROUP BY applied.

Wyjątki

Parametr query jest null lub ciągiem pustym.The query parameter is null or an empty string.

—lub—-or-

Parametr projection jest null lub ciągiem pustym.The projection parameter is null or an empty string.

Przykłady

Ten przykład jest oparty na Microsoft SQL Server przykładach produktu: Database.This example is based on the Microsoft SQL Server Product Samples: Database.

W tym przykładzie tworzony jest nowy obiekt ObjectQuery<T>, który zawiera wyniki istniejącej kwerendy pogrupowane według nazwy produktu.This example creates a new ObjectQuery<T> object that contains the results of the existing query grouped by product name.

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

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

        ObjectQuery<DbDataRecord> productQuery2 =
            productQuery.GroupBy("it.name AS pn",
            "Sqlserver.COUNT(it.Name) as count, pn");

        // Iterate through the collection of Products
        // after the GroupBy method was called.
        foreach (DbDataRecord result in productQuery2)
        {
            Console.WriteLine("Name: {0}; Count: {1}",
                result["pn"], result["count"]);
        }
    }
}
    Using context As New AdventureWorksEntities()
        Dim queryString As String = "SELECT VALUE product " & vbCr & vbLf & " FROM AdventureWorksEntities.Products AS product"

        Dim productQuery As New ObjectQuery(Of Product)(queryString, context, MergeOption.NoTracking)

        Dim productQuery2 As ObjectQuery(Of DbDataRecord) = _
            productQuery.GroupBy("it.name AS pn", "Sqlserver.COUNT(it.Name) as count, pn")

        ' Iterate through the collection of Products 
        ' after the GroupBy method was called. 
        For Each result As DbDataRecord In productQuery2
            Console.WriteLine("Name: {0}; Count: {1}", result("pn"), result("count"))
        Next
    End Using
End Sub

Ten przykład zwraca zestaw zagnieżdżonych rekordów danych, które zawierają Contact.LastName kolumny pogrupowane i posortowane alfabetycznie według pierwszej litery Contact.LastName.This example returns a set of nested data records that contain the Contact.LastName column, grouped and sorted alphabetically by the first letter of Contact.LastName.

using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    // Define the query with a GROUP BY clause that returns
    // a set of nested LastName records grouped by first letter.
    ObjectQuery<DbDataRecord> query =
        context.Contacts
        .GroupBy("SUBSTRING(it.LastName, 1, 1) AS ln", "ln")
        .Select("it.ln AS ln, (SELECT c1.LastName " +
        "FROM AdventureWorksEntities.Contacts AS c1 " +
        "WHERE SubString(c1.LastName, 1, 1) = it.ln) AS CONTACT")
        .OrderBy("it.ln");

    // Execute the query and walk through the nested records.
    foreach (DbDataRecord rec in
        query.Execute(MergeOption.AppendOnly))
    {
        Console.WriteLine("Last names that start with the letter '{0}':",
                    rec[0]);
        List<DbDataRecord> list = rec[1] as List<DbDataRecord>;
        foreach (DbDataRecord r in list)
        {
            for (int i = 0; i < r.FieldCount; i++)
            {
                Console.WriteLine("   {0} ", r[i]);
            }
        }
    }
}
Using context As New AdventureWorksEntities()
    ' Define the query with a GROUP BY clause that returns 
    ' a set of nested LastName records grouped by first letter. 
    Dim query As ObjectQuery(Of DbDataRecord) = _
        context.Contacts.GroupBy("SUBSTRING(it.LastName, 1, 1) AS ln", "ln") _
        .Select("it.ln AS ln, (SELECT c1.LastName FROM AdventureWorksEntities.Contacts AS c1 " & _
                "WHERE SubString(c1.LastName, 1, 1) = it.ln) AS CONTACT").OrderBy("it.ln")

    ' Execute the query and walk through the nested records. 
    For Each rec As DbDataRecord In query.Execute(MergeOption.AppendOnly)
        Console.WriteLine("Last names that start with the letter '{0}':", rec(0))
        Dim list As List(Of DbDataRecord) = TryCast(rec(1), List(Of DbDataRecord))
        For Each r As DbDataRecord In list
            For i As Integer = 0 To r.FieldCount - 1
                Console.WriteLine(" {0} ", r(i))
            Next
        Next
    Next
End Using

Uwagi

GroupBy stosuje projekcję określoną przez parametr projection.GroupBy applies the projection specified by the projection parameter. Oznacza to, że ObjectQuery<T> zwracany przez metodę GroupBy jest zawsze typu DbDataRecord.This means that the ObjectQuery<T> returned by the GroupBy method is always of type DbDataRecord. Aby uzyskać więcej informacji, zobacz zapytania dotyczące obiektów.For more information, see Object Queries.

Dotyczy

Zobacz też