Question

I have 2 datatables in a dataset. One table has a list called CostTypes. Just an Id and Description field.

The other datatable is the master table and has many records and one of the columns is the cost type. There will be cost types that are not reference in this datatable. There is another column in this databale called cost.

What I am trying to do is get a summary by cost type with a total of the cost. But I want ALL cost types listed any values not in the master table will be zero.

CostType table

Id, Description

1,Marketing

2,Sales

3,Production

4,Service

---

Master table

Id, Cost, CostTypeId

1,10,1

2,120,1

3,40,3

So I would like to see a result in a datable (if possible) so I can bind to datagridview

Marketing  130

Sales       0

Production  40

Service     0

Thanks for the help everyone, this is what I came up from the answers – Can anyone suggest any improvements???

Also how can I convert the result in query1 into a datable???

  var query1 =
        from rowCT in costTypes.AsEnumerable()
        from rowSTD in stdRates.AsEnumerable()
              .Where( d => d.Field<int?>( "CostTypeId" ) == rowCT.Field<int?>( "CostTypeId" ) )
              .DefaultIfEmpty()
        group new { row0 = rowCT, row1 = rowSTD }
        by rowCT.Field<string>( "Description" ) into g
        select new
        {
            g.Key,
            Cost = g.Sum( x => x.row1 == null ? 0 : x.row1.Field<decimal>( "Cost" ) ),
            TotalCost = g.Sum( x => x.row1 == null ? 0 : x.row1.Field<decimal>( "TotalCost" ) ),
            TotalHours = g.Sum( x => x.row1 == null ? 0 : x.row1.Field<decimal>( "TotalHours" ) ),
            TotalLabourCost = g.Sum( x => x.row1 == null ? 0 : x.row1.Field<decimal>( "TotalLabourCost" ) )
        }
        ;

Answer 1

Maybe something like this:

Test data:

DataTable dt=new DataTable();
dt.Columns.Add("Id",typeof(int));
dt.Columns.Add("Description",typeof(string));

dt.Rows.Add(1,"Marketing");
dt.Rows.Add(2,"Sales");
dt.Rows.Add(3,"Production");
dt.Rows.Add(4,"Service");

DataTable dt2=new DataTable();
dt2.Columns.Add("Id",typeof(int));
dt2.Columns.Add("Cost",typeof(int));
dt2.Columns.Add("CostTypeId",typeof(int));

dt2.Rows.Add(1,10,1);
dt2.Rows.Add(2,120,1);
dt2.Rows.Add(3,40,1);

Linq query

var query=(
            from row in dt.AsEnumerable()
            from row1 in dt2.AsEnumerable()
                  .Where (d =>d.Field<int>("Id")==row.Field<int>("Id") )
                  .DefaultIfEmpty()
            group new{row,row1} 
            by row.Field<string>("Description") into g 
            select new
            {
                g.Key,
                Cost=g.Sum (x =>x.row1==null?0:x.row1.Field<int>("Cost"))
            }
            );

Result

Key        Cost
Marketing  10
Sales      120
Production 40
Service    0