SqlTypes e DataSetSqlTypes and the DataSet

In ADO.NET 2.0 è stato introdotto il supporto migliorato per i tipi per DataSet tramite lo spazio dei nomi System.Data.SqlTypes.ADO.NET 2.0 introduced enhanced type support for the DataSet through the System.Data.SqlTypes namespace. I tipi System.Data.SqlTypes sono progettati per fornire tipi di dati con la stessa semantica e la stessa precisione dei tipi di dati di un database di SQL Server.The types in System.Data.SqlTypes are designed to provide data types with the same semantics and precision as the data types in a SQL Server database. Ogni tipo di dati in System.Data.SqlTypes dispone di un tipo di dati equivalente in SQL Server, con la stessa rappresentazione di dati sottostante.Each data type in System.Data.SqlTypes has an equivalent data type in SQL Server, with the same underlying data representation.

L'utilizzo di System.Data.SqlTypes direttamente in un oggetto DataSet offre numerosi vantaggi quando si lavora con tipi di dati SQL Server.Using System.Data.SqlTypes directly in a DataSet confers several benefits when working with SQL Server data types. System.Data.SqlTypes supporta la stessa semantica dei tipi di dati nativi SQL Server.System.Data.SqlTypes supports the same semantics as SQL Server native data types. La specifica di uno degli oggetti System.Data.SqlTypes nella definizione di un oggetto DataColumn elimina la perdita di precisione che può verificarsi in caso di conversione di tipi di dati numerici o decimali in uno dei tipi di dati CLR (Common Language Runtime).Specifying one of the System.Data.SqlTypes in the definition of a DataColumn eliminates the loss of precision that can occur when converting decimal or numeric data types to one of the common language runtime (CLR) data types.

EsempioExample

Nell'esempio seguente viene creato un oggetto DataTable, definendo in modo esplicito i tipi di dati DataColumn usando System.Data.SqlTypes invece dei tipi CLR.The following example creates a DataTable object, explicitly defining the DataColumn data types by using System.Data.SqlTypes instead of CLR types. Il codice consente di compilare DataTable con i dati della tabella Sales.SalesOrderDetail nel database AdventureWorks in SQL Server.The code fills the DataTable with data from the Sales.SalesOrderDetail table in the AdventureWorks database in SQL Server. L'output visualizzato nella finestra della console mostra i tipi di dati di ogni colonna e i valori recuperati da SQL Server.The output displayed in the console window shows the data type of each column, and the values retrieved from SQL Server.

static private void GetSqlTypesAW(string connectionString)
{
    // Create a DataTable and specify a SqlType
    // for each column.
    DataTable table = new DataTable();
    DataColumn icolumnolumn =
        table.Columns.Add("SalesOrderID", typeof(SqlInt32));
    DataColumn priceColumn =
        table.Columns.Add("UnitPrice", typeof(SqlMoney));
    DataColumn totalColumn =
        table.Columns.Add("LineTotal", typeof(SqlDecimal));
    DataColumn columnModifiedDate =
        table.Columns.Add("ModifiedDate", typeof(SqlDateTime));

    // Open a connection to SQL Server and fill the DataTable
    // with data from the Sales.SalesOrderDetail table
    // in the AdventureWorks sample database.
    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        string queryString =
            "SELECT TOP 5 SalesOrderID, UnitPrice, LineTotal, ModifiedDate "
            + "FROM Sales.SalesOrderDetail WHERE LineTotal < @LineTotal";

        // Create the SqlCommand.
        SqlCommand command = new SqlCommand(queryString, connection);

        // Create the SqlParameter and assign a value.
        SqlParameter parameter =
            new SqlParameter("@LineTotal", SqlDbType.Decimal);
        parameter.Value = 1.5;
        command.Parameters.Add(parameter);

        // Open the connection and load the data.
        connection.Open();
        SqlDataReader reader =
            command.ExecuteReader(CommandBehavior.CloseConnection);
        table.Load(reader);

        // Close the SqlDataReader.
        reader.Close();
    }

    // Display the SqlType of each column.
    Console.WriteLine("Data Types:");
    foreach (DataColumn column in table.Columns)
    {
        Console.WriteLine(" {0} -- {1}",
            column.ColumnName, column.DataType.UnderlyingSystemType);
    }

    // Display the value for each row.
    Console.WriteLine("Values:");
    foreach (DataRow row in table.Rows)
    {
        Console.Write(" {0}, ", row["SalesOrderID"]);
        Console.Write(" {0}, ", row["UnitPrice"]);
        Console.Write(" {0}, ", row["LineTotal"]);
        Console.Write(" {0} ", row["ModifiedDate"]);
        Console.WriteLine();
    }
}
Private Sub GetSqlTypesAW(ByVal connectionString As String)

    ' Create a DataTable and specify the
    ' SqlType for each column.
    Dim table As New DataTable()
    Dim icolumnolumn As DataColumn = _
      table.Columns.Add("SalesOrderID", GetType(SqlInt32))
    Dim priceColumn As DataColumn = _
      table.Columns.Add("UnitPrice", GetType(SqlMoney))
    Dim totalColumn As DataColumn = _
      table.Columns.Add("LineTotal", GetType(SqlDecimal))
    Dim columnModifiedDate As DataColumn = _
      table.Columns.Add("ModifiedDate", GetType(SqlDateTime))

    ' Open a connection to SQL Server and fill the DataTable
    ' with data from the Sales.SalesOrderDetail table
    ' in the AdventureWorks sample database.
    Using connection As New SqlConnection(connectionString)

        Dim queryString As String = _
           "SELECT TOP 5 SalesOrderID, UnitPrice, LineTotal, ModifiedDate " _
           & "FROM Sales.SalesOrderDetail WHERE LineTotal < @LineTotal"

        ' Create the SqlCommand.
        Dim command As SqlCommand = New SqlCommand(queryString, connection)

        ' Create the SqlParameter and assign a value.
        Dim parameter As SqlParameter = _
           New SqlParameter("@LineTotal", SqlDbType.Decimal)
        parameter.Value = 1.5
        command.Parameters.Add(parameter)

        ' Open the connection and load the data.
        connection.Open()
        Dim reader As SqlDataReader = _
           command.ExecuteReader(CommandBehavior.CloseConnection)
        table.Load(reader)

        ' Close the SqlDataReader
        reader.Close()
    End Using

    ' Display the SqlType of each column.
    Dim column As DataColumn
    Console.WriteLine("Data Types:")
    For Each column In table.Columns
        Console.WriteLine(" {0} -- {1}", _
        column.ColumnName, column.DataType.UnderlyingSystemType)
    Next column

    ' Display the value for each row.
    Dim row As DataRow
    Console.WriteLine("Values:")
    For Each row In table.Rows
        Console.Write(" {0}, ", row("SalesOrderID"))
        Console.Write(" {0}, ", row("UnitPrice"))
        Console.Write(" {0}, ", row("LineTotal"))
        Console.Write(" {0} ", row("ModifiedDate"))
        Console.WriteLine()
    Next row
End Sub

Vedere ancheSee also