C# Not able to use CopyToDataTable() function when grouping fields by LINQ & Datatable

Question

Here I am grouping data by LINQ on DataTable but I was trying to use CopyToDataTable() which was not available on my side. please see my code and tell me what I missed in my code for which CopyToDataTable() not available.

DataTable perioddata = ds.Tables[1].AsEnumerable()
     .GroupBy(a => new
     {
        NewPeriod = a.Field<string?>("NewPeriod").ToString(),
        PeriodOrder = a.Field<int>("PeriodOrder").ToString().ToInt32()
     })
     .Select(b => new PeriodDto
     {
        NewPeriod = b.Key.NewPeriod,
        PeriodOrder = b.Key.PeriodOrder
     }).CopyToDataTable();

With the select you're returning IEnumerable to use CopyToDatatable you need IEnumerable — J.Salas, Apr 21 '22 at 06:45

score 2 · Answer 1 · answered Apr 21 '22 at 07:11

CopyToDataTable works with DataRow which is why you can not use it.

DataTable CopyToDataTable<T>(this IEnumerable<T> source) where T : DataRow

Since you have IEnumerable<PeriodDto>, you can create your own extension method, see: Convert generic List/Enumerable to DataTable?

public static DataTable ToDataTable<T>(this IList<T> data)
{
    PropertyDescriptorCollection props =
        TypeDescriptor.GetProperties(typeof(T));
    DataTable table = new DataTable();
    for(int i = 0 ; i < props.Count ; i++)
    {
        PropertyDescriptor prop = props[i];
        table.Columns.Add(prop.Name, prop.PropertyType);
    }
    object[] values = new object[props.Count];
    foreach (T item in data)
    {
        for (int i = 0; i < values.Length; i++)
        {
            values[i] = props[i].GetValue(item);
        }
        table.Rows.Add(values);
    }
    return table;        
}

without using any extension method how could i restructure my code where i can use CopyToDataTable() function ? you can remove `new PeriodDto` this class. — Ramesh Dutta, Apr 21 '22 at 08:23

score 1 · Accepted Answer · edited Apr 21 '22 at 18:22

1

Without using a generic extension method and using the PeriodDto definition as the expected DataRow definition

DataTable perioddata = ds.Tables[1].AsEnumerable()
   .GroupBy(a => new
   {
       NewPeriod = a.Field<string>("NewPeriod").ToString(),
       PeriodOrder = a.Field<int>("PeriodOrder")
   })
   .Select(b => { 
       DataRow row = ds.Tables[1].NewRow();
       row["NewPeriod"] = b.Key.NewPeriod;
       row["PeriodOrder"] = b.Key.PeriodOrder;
       return row;
   }).CopyToDataTable();

edited Apr 21 '22 at 18:22

Selim Yildiz

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answered Apr 21 '22 at 10:04

J.Salas

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Thanks you so much. – Ramesh Dutta Apr 21 '22 at 14:16

C# Not able to use CopyToDataTable() function when grouping fields by LINQ & Datatable

2 Answers2