Get constant from column ordinal.

[MAW30]

I need to use a DataTable's column number in a switch statement. I am having problems with the following: const Int32 xxxColumn = (Int32)DataTable.xxxColumn.Ordinal; switch (n) { case xxxColumn: ********; break; } How do I get a constant value from a DataTable column ordinal. Any help will be appreciated, Thanks in advance, Michael

[Lost User]

The parameter in a switch statement must be an actual constant whose value is available at compile time. Your code is using a variable that is not available to the compiler. You will need to use an if statement.

[BillWoodruff]

See if this gives you useful ideas:

public class SwitchOnDTOrdinal
{
public SwitchOnDTOrdinal(DataTable table)
{
TheTable = table;

    validColumnNames = table.Columns
        .Cast()
        .Select(col => col.ColumnName)
        .ToList();
}

private List validColumnNames;

private DataTable TheTable;

public void SwitchA(string cname)
{
    if (! validColumnNames.Contains(cname))
    {
        throw new ArgumentException(@"{cname} is not a valid column name");
    }

    switch(TheTable.Columns\[cname\].Ordinal)
    {
        case 0:
            break;
        case 1:
            break;
        case 2:
            break;
        case 3:
            break;
        default:
            throw new ArgumentOutOfRangeException();
    }
}

}

«One day it will have to be officially admitted that what we have christened reality is an even greater illusion than the world of dreams.» Salvador Dali

[Luc Pattyn]

Hi, for Ordinal I agree with what has already been said. However you might consider working with the columns Name or Caption property; if one of those has known values you can still use a simple switch, as C# allows switching on string literals. :)

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