Specifies a response variable for server-side sorting. If omitted, client-side sorting is used. The response is a numeric value that represents a column in the grid. Each grid column is identified by a sequential index, starting with 0 for the first column, 1 for the second column, and so on. It is the responsibility of the program to keep track of the sort direction, and to display an up or down arrow in the appropriate column using the Initial Sort Column and Default Sort Order properties.
Possible Values: Must be bound