OleDbDataReader.GetOrdinal(String) 方法

public:
 override int GetOrdinal(System::String ^ name);

public:
 virtual int GetOrdinal(System::String ^ name);

public override int GetOrdinal(string name);

public int GetOrdinal(string name);

override this.GetOrdinal : string -> int

abstract member GetOrdinal : string -> int
override this.GetOrdinal : string -> int

Public Overrides Function GetOrdinal (name As String) As Integer

Public Function GetOrdinal (name As String) As Integer

参数

返回

从零开始的列序号。

实现

例外

示例

下面的示例演示如何使用 GetOrdinal 方法。

public static void ReadData(string connectionString)
{
    string queryString = "SELECT DISTINCT CustomerID FROM Orders";
    using (OleDbConnection connection = new OleDbConnection(connectionString))
    {
        OleDbCommand command = new OleDbCommand(queryString, connection);

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

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

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

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

    Using connection As New OleDbConnection(connectionString)
        Dim command As New OleDbCommand(queryString, connection)

        connection.Open()

        Dim reader As OleDbDataReader = command.ExecuteReader()

        Dim customerID As Integer = reader.GetOrdinal("CustomerID")
        While reader.Read()
            Console.WriteLine("CustomerID={0}", reader.GetString(customerID))
        End While
        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。 如果未找到从零开始的列序号， 方法将 IndexOutOfRange 引发异常。

GetOrdinal 不区分假名宽度。

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。

另请参阅

• DataAdapter 和 DataReader