IDataReader.Read 方法

public:
 bool Read();

public bool Read();

abstract member Read : unit -> bool

Public Function Read () As Boolean

返回

true 如果有更多行，则为否则，为 false.

示例

以下示例创建三个派生类、一个OleDbConnection和一个OleDbCommand派生类OleDbDataReader的实例。 该示例读取数据，并将其写出到控制台。 最后，该示例关闭 OleDbDataReader，然后关闭 OleDbConnection。

private static void ReadData(string connectionString)
{
    string queryString = "SELECT OrderID, CustomerID FROM Orders";
    using (OracleConnection connection = new OracleConnection(connectionString))
    {
        OracleCommand command = new OracleCommand(queryString, connection);
        connection.Open();
        OracleDataReader reader;
        reader = command.ExecuteReader();

        // Always call Read before accessing data.
        while (reader.Read())
        {
            Console.WriteLine(reader.GetInt32(0) + ", " + reader.GetString(1));
        }

        // Always call Close when done reading.
        reader.Close();
    }
}

Public Sub ReadData(ByVal connectionString As String)
    Dim queryString As String = _
        "SELECT OrderID, CustomerID FROM Orders"

    Using connection As New OracleConnection(connectionString)
        Dim command As New OracleCommand(queryString, connection)
        connection.Open()

        Dim reader As OracleDataReader
        reader = command.ExecuteReader()

        ' Always call Read before accessing data.
        While reader.Read()
            Console.WriteLine(reader.GetInt32(0) & ", " & reader.GetString(1))
        End While

        ' Always call Close when done reading.
        reader.Close()
    End Using
End Sub

注解

默认位置 IDataReader 位于第一条记录之前。 因此，必须调用 Read 才能开始访问任何数据。

当数据读取器正在使用时，关联的连接正忙于 IDataReader提供 。 这种情况一直 Close 持续到调用为止。