Compare two csv files in C#

Question

I want to compare two csv files and print the differences in a file. I currently use the code below to remove a row. Can I change this code so that it compares two csv files or is there a better way in c# to compare csv files?

 List<string> lines = new List<string>(); using (StreamReader reader = new StreamReader(System.IO.File.OpenRead(path))) { string line; while ((line = reader.ReadLine()) != null) { if (line.Contains(csvseperator)) { string[] split = line.Split(Convert.ToChar(scheidingsteken)); if (split[selectedRow] == value) { } else { line = string.Join(csvseperator, split); lines.Add(line); } } } } using (StreamWriter writer = new StreamWriter(path, false)) { foreach (string line in lines) writer.WriteLine(line); } }

If you want to find out added, deleted and changed lines, please have a look at the edit distance en.wikipedia.org/wiki/Edit_distance — Dmitrii Bychenko
– Dmitrii Bychenko, Commented Oct 11, 2017 at 12:48
Why are you so sad? Why can't you use it? The easiest edit distance (Levenshtein one) is easy to implement en.wikipedia.org/wiki/Levenshtein_distance — Dmitrii Bychenko
– Dmitrii Bychenko, Commented Oct 11, 2017 at 13:09
You really shouldn't use empty if blocks in your code. Changing the condition solves this issue. — Markus Deibel
– Markus Deibel, Commented Oct 11, 2017 at 13:15
What do you want your program to output when two CSV files contain exactly the same data, but in a different order? Also, do records need to match 100%? Or is 1,Pete,2 equal to 1,"Pete",2? — C.Evenhuis
– C.Evenhuis, Commented Oct 11, 2017 at 13:30

Cinchoo · Accepted Answer · 2021-11-26 19:48:58Z

Here is another way to find differences between CSV files, using Cinchoo ETL - an open source library

For the below sample CSV files

sample1.csv

id,name 1,Tom 2,Mark 3,Angie

sample2.csv

id,name 1,Tom 2,Mark 4,Lu

METHOD 1:

Using Cinchoo ETL, below code shows how to find differences between rows by all columns

var input1 = new ChoCSVReader("sample1.csv").WithFirstLineHeader().ToArray(); var input2 = new ChoCSVReader("sample2.csv").WithFirstLineHeader().ToArray(); using (var output = new ChoCSVWriter("sampleDiff.csv").WithFirstLineHeader()) { output.Write(input1.OfType<ChoDynamicObject>().Except(input2.OfType<ChoDynamicObject>(), ChoDynamicObjectEqualityComparer.Default)); output.Write(input2.OfType<ChoDynamicObject>().Except(input1.OfType<ChoDynamicObject>(), ChoDynamicObjectEqualityComparer.Default)); }

sampleDiff.csv

id,name 3,Angie 4,Lu

Sample fiddle: https://dotnetfiddle.net/nwLeJ2

METHOD 2:

If you want to do the differences by id column,

var input1 = new ChoCSVReader("sample1.csv").WithFirstLineHeader().ToArray(); var input2 = new ChoCSVReader("sample2.csv").WithFirstLineHeader().ToArray(); using (var output = new ChoCSVWriter("sampleDiff.csv").WithFirstLineHeader()) { output.Write(input1.OfType<ChoDynamicObject>().Except(input2.OfType<ChoDynamicObject>(), new ChoDynamicObjectEqualityComparer(new string[] { "id" }))); output.Write(input2.OfType<ChoDynamicObject>().Except(input1.OfType<ChoDynamicObject>(), new ChoDynamicObjectEqualityComparer(new string[] { "id" }))); }

Sample fiddle: https://dotnetfiddle.net/t6mmJW

This is a great tool. Thank you. In my case I have a "master" CSV file and a "detail" CSV file. How can I do the same above where CSV 1 is the master and CSV 2 is the detail to ouput a file saying record '3' has been "deleted" and record "4" is new? Obviously a new column to show this status. Could you please add an example to your answer? Oh and my CSVs have a unique ID column like your samples. Appreciated.

Ian Vos · Accepted Answer · 2017-10-11 14:10:33Z

If you only want to compare one column you can use this code:

 List<string> lines = new List<string>(); List<string> lines2 = new List<string>(); try { StreamReader reader = new StreamReader(System.IO.File.OpenRead(pad)); StreamReader read = new StreamReader(System.IO.File.OpenRead(pad2)); string line; string line2; //With this you can change the cells you want to compair int comp1 = 1; int comp2 = 1; while ((line = reader.ReadLine()) != null && (line2 = read.ReadLine()) != null) { string[] split = line.Split(Convert.ToChar(seperator)); string[] split2 = line2.Split(Convert.ToChar(seperator)); if (line.Contains(seperator) && line2.Contains(seperator)) { if (split[comp1] != split2[comp2]) { //It is not the same } else { //It is the same } } } reader.Dispose(); read.Dispose(); } catch { }

This only checks the 2nd column of each line, and ignores lines if one CSV contains more lines than the other.

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