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DataTableReader.GetOrdinal Method

Note: This method is new in the .NET Framework version 2.0.

Gets the column ordinal, given the name of the column.

Namespace: System.Data
Assembly: System.Data (in system.data.dll)

public override int GetOrdinal (
	string name
)
public int GetOrdinal (
	String name
)
public override function GetOrdinal (
	name : String
) : int

Parameters

name

The name of the column.

Return Value

The zero-based column ordinal.

Exception typeCondition

InvalidOperationException

An attempt was made to read or access a column in a closed DataTableReader.

ArgumentException

The name specified is not a valid column name.

Because most of the methods provided by the DataTableReader class must be provided with an ordinal column number, you can use the GetOrdinal method to retrieve the column number, given the name of the column.

GetOrdinal performs a case-sensitive lookup first. If it fails, a second case-insensitive search is made.

GetOrdinal is kana-width insensitive.

Because ordinal-based lookups are more efficient than named lookups, it is inefficient to call GetOrdinal within a loop. Save time by calling GetOrdinal one time and assigning the results to an integer variable for use within the loop

If you have only a column name, in which case the column name is user supplied, and you must retrieve information from the column, you can use a procedure like the following to extract the required information. In this example, the procedure accepts a column name and returns the data that is contained within that column for the current row in the DataTableReader :

private static object GetValueByName(
    DataTableReader reader, string columnName)
{
    // Consider when to use a procedure like this one carefully:
    // if you're going to retrieve information from a column
    // in a loop, it would be better to retrieve the column
    // ordinal once, store the value, and use the methods
    // of the DataTableReader class directly. 
    object columnValue;

    try
    {
        int columnOrdinal = reader.GetOrdinal(columnName);
        columnValue = reader.GetValue(columnOrdinal);
    
    catch (ArgumentException ex)
    {
        // Throw all other errors back out to the caller.
        columnValue = null;
    
    return columnValue;



Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0

.NET Compact Framework

Supported in: 2.0

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