Detect duplicate entries in datatable rows


I have a datatable with the following columns:

givenname, surname, title, dept, identifier

Now I have thousands of rows like this for each user in the company:


As some of the users have the same name, I have something like this:


Now I want to detect these users and write the identifier (as this is unique) of these users to a list(of string).

How can I do that?

Thanks, Jan
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janwrageAuthor Commented:
Hi again,

I know I could read one rows data (givenname, surname) and then loop thru the remaining and compare it to them.
But this is very time-consuming as for each entry, I need to loop thru all remaining rows and this is very slow.


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I think if you use the group by clause in the SQL statement when loading data, it should group the names together and give you the count, For example
Select GivenName, Surname, Count(Surname) From Table Group By GivenName, Surname
janwrageAuthor Commented:
How do I do that in VB?

The table is filled by some CSV-Parser, so no SQL...
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Then you need to loop through the table i think. Or if you are using VB.NET 2008, try using LINQ. Check out these links
janwrageAuthor Commented:
Thx, I'll check it out.
did provide a solution which the asker choose not to implement
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