You can make a new DataTable, then import rows of two tables into new table.

DataTable t = new DataTable();
t.Columns.Add("Product", typeof(string));
t.Columns.Add("Value", typeof(int));

foreach(DataTable table in SampleDS.Tables)
{
if(table != null && table.Rows.Count > 0)
{
for(int i = 0; i < table.Rows.Count; i ++)
t.ImportRow(table.Rows[i]);
}
}