How can we sort datatables in C#.net?

You can't sort DataTable directly,
for to sort DataTable convert it to GrideView

or convert it into DataView
here is the sample code that may helps you.

DataTable dt = new DataTable();
           DataRow dr;

           // Define the columns of the table.
           dt.Columns.Add(new DataColumn("IntegerValue", typeof(Int32)));
           dt.Columns.Add(new DataColumn("StringValue", typeof(string)));
           dt.Columns.Add(new DataColumn("CurrencyValue", typeof(double)));

           // Populate the table with sample values.
           for (int i = 0; i < 5; i++)
           {
               dr = dt.NewRow();

               dr[0] = i;
               dr[1] = "Item " + i.ToString();
               dr[2] = 5.23 * ((5-i) + 1);

               dt.Rows.Add(dr);
           }
           DataView dv = new DataView(dt);
           dv.Sort = "CurrencyValue";
           dt = dv.ToTable();

sort property of DataView takes string type, that contains the column name followed by "ASC" (ascending) or "DESC" (descending). Columns are sorted ascending by default. Multiple columns can be separated by commas.

dv.Sort = "CurrencyValue DESC";

Go throuth this URl below

http://forums.asp.net/t/1396828.aspx/1[^]

http://weblogs.asp.net/vikram/archive/2008/02/13/sorting-dataview-on-multiple-columns.aspx[^]

Google! It found this as the top answer, using your subject as the query: Filtering and Sorting Directly in Data Tables[^]

You can filter and sort the contents of a data table directly by calling a table's Select method.
Try
MSDN-[Filtering and Sorting Directly in Data Tables][^]