Comparing two csv files and outputting values

Question

I got two .csv files as shown below:

1st file:

"id"
4
1
3

2nd file:

"id"
1
2
3
4
5

I would like to check whether in first file there are all values from second file (no matter in which row they are). In my example in 1st file 2 and 5 values missing comparing to 2nd file so i would like to output somehow those values. How can i do that?

Does this answer your question? How to compare 2 List<string> objects to get the missing value from the List<string> — Drag and Drop
– Drag and Drop, Commented Mar 1, 2021 at 10:39
Key word for find those where "not in" or "except" for the first link and "File to list string" for the second. — Drag and Drop
– Drag and Drop, Commented Mar 1, 2021 at 10:41
Load your CSV using CsvHelper for example, and then you can work with your record lists as usual to perform comparison between them. — XavierA
– XavierA, Commented Mar 1, 2021 at 10:43

Tim Schmelter · Accepted Answer · 2021-03-01 10:51:56Z

2

So you know how to read them and don't know how to find out which are missing? You can use Enumerable.Except

IEnumerable<string> firstFileIds = GetFileIds(...);
IEnumerable<string> secondFileIds = GetFileIds(...);
IEnumerable<string> missingInFirst = secondFileIds.Except(firstFileIds);

Console.Write($"Missing in 1st file: {string.Join(",", missingInFirst)}");

edited Mar 1, 2021 at 10:51

answered Mar 1, 2021 at 10:46

Tim Schmelter

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3 Comments

Henry Over a year ago

Error: cannot convert from 'System.Collections.Generic.IEnumerable<string>' to 'char'

Henry Over a year ago

Just additional question, do you know how to list duplicates out first list?

Tim Schmelter Over a year ago

@Henry: var dups=firstFileIds.GroupBy(id=>id).Where(g=>g.Count()>1).Select(g=>g.Key);. Instead of g.Count()>1 you can also use g.Skip(1).Any() since that could be more efficient

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