Question

I have a database table that I am using as a source for a report. The table layout looks
like. Table 1 is subset of a larger database table. But for the report I only need certain columns So I am creating a new data table by using the function given below

Value  Description   Hours
    1          A           2
    2          B           3
    3          C           5
    1          A           3
    2          B           4
    2          B           3
    3          C           3


private DataTable CreateFocusOfEffortData()
    {
        var dtChartData = new DataTable();
        dtChartData.Columns.Add("Description", typeof(string));
        dtChartData.Columns.Add("Hours", typeof(Double));
        var myDataView = ReportData.DefaultView;
        myDataView.RowFilter = "ActivityUnitID = " + _ActivityUnitID;
        for (var i = 0; i < myDataView.ToTable().Rows.Count; i++)
        {
            var dataRow = new Object[dtChartData.Columns.Count];
            dataRow[0] = ReportData.Rows[i]["Description"];
            dataRow[1] = csaConvert.ToDouble(ReportData.Rows[i]["Hours"]);
            dataRow[2] = ReportData.Rows[i]["Value"];
            dtChartData.Rows.Add(dataRow);
        }
        return dtChartData;
    }

Now I need to design another report with summary data from above table. This table should
combine data for all the columns based on Column[“Value]. for example in my case we have three distinct values in Value column 1,2,3. The resulting table should have hours summed up for all the three values.

    Value   Description  Hours
    1         A           5
    2         B           10
    3         C           8

Now I can do this in sql by creating another stored proc but I would rather use my existing data-table and write a C# function to get the result. Is there a easier way to achieve this using LINQ?

Answer 1

You can use AsEnumerable() in order to use LINQ, then GroupBy by Value and Description and do Sum on Hours to set for the first row:

var result = dtChartData.AsEnumerable()
            .GroupBy(row => new
                {
                    Value = row.Field<int>("Value"),
                    Description = row.Field<string>("Description")
                })
            .Select(g =>
                {
                    var row = g.First();
                    row.SetField("Hours", g.Sum(r => r.Field<double>("Hours")));

                    return row;
                });

The result will return IEnumerable<DataRow> but if you want to get DataTable back, use:

var resultTable = result.CopyToDataTable();