DataTable myTable = new DataTable("Customers");
...
DataColumn cCustID = new DataColumn("CustID", typeof(int));
cCustID.AutoIncrement = true;
cCustID.AutoIncrementSeed = 1;
cCustID.AutoIncrementStep = 1;
myTable.Columns.Add(cCustID);
Contributed from George Shepherd's Windows Forms FAQ