Fill a DataSet or a DataTable from a LINQ query resultset

MyDataContext db = new MyDataContext();
IEnumerable<DataRow> query = 
         (from order in db.Orders.AsEnumerable()
          select new
          {
           order.Property,
           order.Property2
          }) as IEnumerable<DataRow>;
return query.CopyToDataTable<DataRow>();

Read excel data into dataset

OleDbConnection con = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\\Data\\Book1.xls;Extended Properties=""Excel 8.0;HDR=YES;""");
con.Open();
OleDbDataAdapter da = new OleDbDataAdapter("select * from [Sheet4$]", con);
DataSet ds = new DataSet();
da.Fill(ds);

for (Int32 i = 0; i < ds.Tables[0].Rows.Count; i++)
{
//Implement your logic here
}