How to sort DataTable by two columns in c#

You can use LINQ to DataSet/DataTable

var newDataTable = yourtable.AsEnumerable()
                   .OrderBy(r=> r.Field<int>("ItemIndex"))
                   .ThenBy(r=> r.Field<int>("ItemValue"))  
                   .CopyToDataTable();

Create a DataView and use the Sort Property:

DataView dv = new DataView(dt);
dv.Sort = "ItemIndex, ItemValue";

e.g.

foreach (DataRowView row in dv) {
   Console.WriteLine(" {0} \t {1}", row["ItemIndex"], row["ItemValue"]);
}

For more information, check out MDSN for a more thorough example:

http://msdn.microsoft.com/en-us/library/system.data.dataview.sort.aspx

On the datatable object, just get the defaultview object and set the sort.

dataTable.DefaultView.Sort = "ItemIndex, ItemValue";