Send the Set Selected message to select a column.
colList = dt << Get Column Names( String );
If you want to select many columns, consider sending the Select Columns message to the data table. See Select Columns in a Data Table.
To get a list of currently selected columns, use the Get Selected Columns message.
dt << Get Selected Columns();
Return the list of selected columns as a string using the "string" argument:
To actually select the columns before getting the columns, send the Set Selected message to a column. For more information, see Column Attributes.
To select and move to a specific column, use the Go To message.
To select any column that is currently deselected and deselect any column that is currently selected, use the Invert Column Selection message.
Wait( 1 );
b = dt << Invert Column Selection;
b = dt << Invert Column Selection( a );