Linq query - group by column that does not exist in table

Question

List of columns from Table1

string groupByColumnsJoined = string.Format("new ({0})", String.Join(", ", groupByColumns));  

Using dynamic group by to query Table2

                var query = dataTable2  

                                .AsEnumerable()
                                .AsQueryable()
                                .GroupBy(groupByColumnsJoined, "it")
                                .Select("it.First()");

The groupByColumnsJoined may contain column names that are not part of Table2 (dataTable2). How to handle the Linq query in this scenario?

Answer 1

@Zeeshan Dar , you could remove the unused column names in the databale2.

Here is a code example you could refer to:

var groupByColumns =new List<string>() {"Name","Age","Id","Address" };

    string groupByColumnsJoined = string.Format("new ({0})", String.Join(", ", groupByColumns));  

    var dataTable2 = new DataTable();  
    dataTable2.Columns.Add("Name");  
    dataTable2.Columns.Add("Age");  
    dataTable2.Columns.Add("Id");  
    dataTable2.Rows.Add("test1",22,1001);  
    dataTable2.Rows.Add("test2", 23, 1002);  
    dataTable2.Rows.Add("test3", 24, 1003);  
    List<string> list2 = new List<string>();  

    foreach (DataColumn item in dataTable2.Columns)  
    {  
        list2.Add(item.ColumnName);  
    }  
    IEnumerable<string> result = groupByColumns.Intersect(list2);  
    var list1 = (from DataRow dr in dataTable2.Rows  
                 select new  
                 {  
                     Name = dr["Name"].ToString(),  
                     Age = Convert.ToInt32(dr["Age"].ToString()),  
                     Id = Convert.ToInt32(dr["Id"].ToString()),  
                 }).ToList();  

    var query = list1.GroupBy(result, "it")  
                        .Select("it");  

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