HOW TO：執行可傳回複雜類型的查詢 (EntityClient)

本主題示範如何使用 EntityCommand 來執行可傳回複雜類型的 實體 SQL 查詢。此範例使用 HOW TO：定義具有複雜類型的模型 (Entity Framework) 中所定義的結構描述。如需設定專案的詳細資訊，以及如何使用物件服務來執行可傳回複雜類型之查詢的範例，請參閱 HOW TO：使用複雜類型來建立和執行物件查詢 (Entity Framework)。

範例

下列範例示範如何建立及執行具有複雜類型的查詢。複雜類型代表包含類似實體類型的屬性集、但不包含索引鍵屬性的型別。下列 CCustomer 實體的 Address 屬性會實作成複雜類型。下列範例會輸出 CCustomer 型別的兩個屬性：CustomerId 和 Address。由於 Address 是複雜類型，所以程式碼會輸出 Address 的屬性值。

Using conn As EntityConnection = New EntityConnection("name=CustomerComplexAddrContext")
    conn.Open()

    ' Create an EntityCommand.
    Using cmd As EntityCommand = conn.CreateCommand()

        ' Create a query that returns Address complex type.
        Dim esqlQuery As String = "SELECT VALUE customers FROM " & _
            "CustomerComplexAddrContext.CCustomers " & _
            "AS customers WHERE customers.CustomerId < 3"
        cmd.CommandText = esqlQuery
        ' Execute the command.
        Using rdr As EntityDataReader = cmd.ExecuteReader(CommandBehavior.SequentialAccess)
            ' The result returned by this query contains 
            ' Address complex Types.
            Do While rdr.Read
                ' Display CustomerID
                Console.WriteLine("Customer ID: {0}", _
                    rdr.Item("CustomerId"))
                ' Display Address information.
                Dim nestedRecord As DbDataRecord = DirectCast(rdr.Item("Address"), DbDataRecord)
                Console.WriteLine("Address:")
                For i = 0 To nestedRecord.FieldCount - 1
                    Console.WriteLine("  " + nestedRecord.GetName(i) & _
                            ": " + nestedRecord.GetValue(i))
                Next i
            Loop
        End Using
    End Using
    conn.Close()
End Using

using (EntityConnection conn =
    new EntityConnection("name=CustomerComplexAddrContext"))
{
    conn.Open();

    // Create a query that returns Address complex type.
    string esqlQuery =
        @"SELECT VALUE customers FROM
            CustomerComplexAddrContext.CCustomers
            AS customers WHERE customers.CustomerId < 3";
    try
    {
        // Create an EntityCommand.
        using (EntityCommand cmd = conn.CreateCommand())
        {
            cmd.CommandText = esqlQuery;
            // Execute the command.
            using (EntityDataReader rdr =
                cmd.ExecuteReader(CommandBehavior.SequentialAccess))
            {
                // The result returned by this query contains 
                // Address complex Types.
                while (rdr.Read())
                {
                    // Display CustomerID
                    Console.WriteLine("Customer ID: {0}",
                        rdr["CustomerId"]);
                    // Display Address information.
                    DbDataRecord nestedRecord =
                        rdr["Address"] as DbDataRecord;
                    Console.WriteLine("Address:");
                    for (int i = 0; i < nestedRecord.FieldCount; i++)
                    {
                        Console.WriteLine("  " + nestedRecord.GetName(i) +
                            ": " + nestedRecord.GetValue(i));
                    }
                }
            }
        }
    }
    catch (EntityException ex)
    {
        Console.WriteLine(ex.ToString());
    }
    conn.Close();
}

另請參閱

其他資源

使用 EntityClient (Entity Framework 工作)