IDataRecord.GetOrdinal(String) 方法

定义

返回已命名字段的索引。

public:
 int GetOrdinal(System::String ^ name);
public int GetOrdinal (string name);
abstract member GetOrdinal : string -> int
Public Function GetOrdinal (name As String) As Integer

参数

name
String

要查找的字段的名称。

返回

已命名字段的索引。

示例

下面的示例演示如何使用继承 GetOrdinal 的方法。

public static void ReadData(string connectionString)
{
    string queryString = "SELECT DISTINCT CustomerID FROM Orders";

    using (OdbcConnection connection = new OdbcConnection(connectionString))
    {
        OdbcCommand command = new OdbcCommand(queryString, connection);

        connection.Open();
        OdbcDataReader reader = command.ExecuteReader();

        int customerID = reader.GetOrdinal("CustomerID");

        while (reader.Read())
        {
            Console.WriteLine("CustomerID={0}", reader.GetString(customerID));
        }

        // Call Close when done reading.
        reader.Close();
    }
}
Public Sub ReadData(ByVal connectionString As String)
    Dim queryString As String = "SELECT DISTINCT CustomerID FROM Orders"

    Using connection As New OdbcConnection(connectionString)
        Dim command As New OdbcCommand(queryString, connection)

        connection.Open()

        Dim reader As OdbcDataReader = command.ExecuteReader()

        Dim customerID As Integer = reader.GetOrdinal("CustomerID")

        While reader.Read()
            Console.WriteLine("CustomerID={0}", reader.GetString(customerID))
        End While

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

注解

GetOrdinal 首先执行区分大小写的查找。 如果失败,则进行第二次不区分大小写的搜索。 GetOrdinal 不区分假名宽度。 如果未找到命名字段的索引, IndexOutOfRangeException 则会引发 。

因为基于序号的查找比命名查找更高效,因此在循环内调用 GetOrdinal 效率低下。 通过调用 GetOrdinal 一次并将结果分配给整数变量以在循环中使用来节省时间。

适用于