小编Syl*_*ski的帖子

我有一个包含 4 列的数据表，如下所示：

    private static DataSet dataSet;
    private const string tableName = "MyTable";
    private const string columnName1 = "Supplier";  //Column names
    private const string columnName2 = "Invoice";
    private const string columnName3 = "Item";
    private const string columnName4 = "Amount";

我按供应商、发票列对表进行了分组，并使用以下 linq 查询计算了金额的总和：

    private static DataTable GroupQueryA(DataTable dataTable)
    {
        DataTable groupedTable = dataTable.AsEnumerable()
            .GroupBy(r => new { Key1 = r.Field<string>(columnName1), Key2 = r.Field<string>(columnName2) })
            .Select(g => new GroupSum
            {
                Key1 = g.Key.Key1,
                Key2 = g.Key.Key2,
                Sum = g.Sum(x => x.Field<double>(columnName4))
            }).PropertiesToDataTable<GroupSum>(); …