How to replace duplicates in datatable

Question

I have Datatable 1:-----------------------------should be like that:

ID   Name  Lastname             ID     Name   Lastname
-------------------             -----------------------
1  |  koki  ha                  1   |   koki     ha
-------------------                 | ----------------- //merge Rows[0][0]          
1  |  lola  mi                      |   lola     mi     //with Rows[1][0] if the same
-------------------             -----------------------                      
2  |  ka    xe                  2       ka      xe

how to replace "1" with "" or empty if is already exist? I spend for this for 2 hours but can't find the solution. I tried with linq but dont find the key to do it right, maybe distinct or group?

DataTable table = new DataTable("table");
table.Columns.Add("ID", typeof(Int32));
table.Columns.Add("Name", typeof(String)); 
table.Columns.Add("Lastname", typeof(String));

object[] o1 = { 1, "Kiki", "ha"};
        object[] o2 = { 1,"lola","mi"};
        object[] o4 = { 2, "ka", "xe" };
table.Rows.Add(o1);
        table.Rows.Add(o2);
        table.Rows.Add(o4);
dataGridView2.DataSource = table;

Question is when do you want this? You already have data with duplicates? — Andrey, Oct 10 '12 at 14:21
[What have you tried?](http://mattgemmell.com/2008/12/08/what-have-you-tried/) — Darin Dimitrov, Oct 10 '12 at 14:22
yes, i already have data with duplicates, now i want to replace it, or remove it — Uni Le, Oct 10 '12 at 14:22
You should considering using a distinct selection in your LINQ...that will condense the duplicates together: [How can I do SELECT UNIQUE with LINQ?](http://stackoverflow.com/questions/3519165/how-can-i-do-select-unique-with-linq). — Jeremy, Oct 10 '12 at 14:23
distinct doesn't work because it arrase the row, i want to replace duplicates with empty space or " " — Uni Le, Oct 10 '12 at 14:32
Yeah - But in your real-life code? Just a `Fill`? I mean, if you construct it by any kind of looping through source data, that should be the place to start. — Gert Arnold, Oct 10 '12 at 15:06
http://social.msdn.microsoft.com/Forums/en/csharpgeneral/thread/cbbaf1e8-516c-4d0a-a2de-ca396b0f3665 — Bill the Lizard, Nov 29 '12 at 13:21

score 1 · Answer 1 · answered Oct 10 '12 at 15:03

1

Here's how you can do this using LINQ:

var dataRows = table.Rows.Cast<System.Data.DataRow>()
                         .GroupBy(r => r[0])
                         .Where(g => g.Count() > 1); 

foreach (var dataRowGroup in dataRows) {
    int idx = 0;
    foreach (DataRow row in dataRowGroup) {
        if (idx++ > 0) {
            row[0] = DBNull.Value;
        }
    }
}

answered Oct 10 '12 at 15:03

Jay Riggs

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i tried your code but it throws me a table with key header and nothing more – Uni Le Oct 10 '12 at 16:55
@UniLe Then your sample code isn't representative if your actual code; when I use your code to create a DataTable and my code to update it I get the before and after results you say you need. I'm sure we can do what you need to do using LINQ, but that's not so important now that you've found a solution. – Jay Riggs Oct 10 '12 at 18:23

How to replace duplicates in datatable

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