Get unique values from entire table.

protected void Page_Load(object sender, System.EventArgs e)
{
 Data.DataSet DataSet1 = new Data.DataSet();
 DataSet1.ReadXml("C:\\Temp\\DataTable1.xml");
 Data.DataTable DataTable1 = DataSet1.Tables(0);
 Data.DataTable UniqueValuesInDataTable = GetUniqueTableValues(DataTable1);
}

protected Data.DataTable GetUniqueTableValues(Data.DataTable ValuesDataTable)
{
 Data.DataTable ReturnValuesDataTable = null;
 Data.DataTable UniqueColumnValuesDataTable = new Data.DataTable();
 UniqueColumnValuesDataTable.Columns.Add("UniqueValues");
 foreach (Data.DataColumn ValuesDataColumn in ValuesDataTable.Columns) {
  Data.DataTable UniqueValuesInThisColumnDataTable = ValuesDataTable.DefaultView.ToTable(true, ValuesDataColumn.ColumnName);
  UniqueValuesInThisColumnDataTable.Columns(0).ColumnName = "UniqueValues";
  foreach (Data.DataRow UniqueValuesDataRow in UniqueValuesInThisColumnDataTable.Rows) {
   UniqueColumnValuesDataTable.ImportRow(UniqueValuesDataRow);
  }
 }
 UniqueColumnValuesDataTable.DefaultView.Sort = "UniqueValues";
 ReturnValuesDataTable = UniqueColumnValuesDataTable.DefaultView.ToTable(true, "UniqueValues");
 return ReturnValuesDataTable;
}