Remove Column from Data Table C#

Question

Im currently mapping fields from an uploaded excel document to a data table. I want the columns that are not selected to be removed but they still show.

Here is my code:

if(DT.Columns.IndexOf("First Name") != -1)
                DT.Columns["First Name"].ColumnName = "First NameMap";
            DT.Columns[mapping.FirstNameColumnId].ColumnName = "First Name";

            if (DT.Columns.IndexOf("Last Name") != -1)
                DT.Columns["Last Name"].ColumnName = "Last NameMap";
            DT.Columns[mapping.LastNameColumnId].ColumnName = "Last Name";

            if (DT.Columns.IndexOf("Email Address") != -1)
                DT.Columns["Email Address"].ColumnName = "Email AddressMap";
            DT.Columns[mapping.EmailColumnId].ColumnName = "Email Address";


            int ColumnCounter = 0;
            foreach(DataColumn column in DT.Columns)
            {
                if(ColumnCounter != mapping.FirstNameColumnId && ColumnCounter != mapping.LastNameColumnId && ColumnCounter != mapping.EmailColumnId)
                {
                    DT.Columns.Remove(column);
                }
            }

When you step through this code in the debugger, where specifically does it fail? Is that `foreach` loop entered at all? Is the `if` statement therein entered at all? When you call `.Remove()` on the target column, is it removed from that object? — David, Nov 01 '17 at 11:56
The code isnt failing as such. It goes into the DT.Columns.Remove(column); but all the original columns from the excel sheet are still being displayed. I just want it to show the first name , last name, and email — Smac, Nov 01 '17 at 11:58
You should beware of modifying the Columns collection within the foreach - to be safe make a copy with .ToList() - https://stackoverflow.com/questions/14413099/changing-collection-inside-foreach — PaulF, Nov 01 '17 at 11:58
As PaulF said, you should not modify a collection within its own foreach loop. You can use a copy as he says, or use a For loop, but be careful the index will change when an item is removed from the collection. You could also just use a lambda expression to filter the columns to whatever columns you want. — Ricardo Olivo Poletti, Nov 01 '17 at 12:06

score 6 · Accepted Answer · answered Nov 01 '17 at 11:55

6

   DataTable t;
   t.Columns.Remove("columnName");
   t.Columns.RemoveAt(columnIndex);

answered Nov 01 '17 at 11:55

Sunny Jangid

578
4
19

Remove Column from Data Table C#

1 Answers1