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

3

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

edited Nov 26, 2021 at 19:48

answered Oct 11, 2017 at 23:24

Cinchoo

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4 Comments

Fandango68 Over a year ago

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.

Cinchoo Over a year ago

Here u go dotnetfiddle.net/LIHZBv

mully Over a year ago

@Chinchoo Where does the result file get stored to?

Cinchoo Over a year ago

can be routed to file, stream etc.

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

0

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
    {

    }

edited Oct 11, 2017 at 14:10

answered Oct 11, 2017 at 13:41

Ian Vos

491 silver badge6 bronze badges

2 Comments

C.Evenhuis Over a year ago

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

Mylan Over a year ago

How can I fix this?

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