Concatenating lists horizontally C#

Question

I'm using the CsvHelper library tool to help write lists that I've created to CSV file.

using (var sr = new StreamReader(inPath))
{
    using (var sw = new StreamWriter(outPath))
    {
        var reader = new CsvReader(sr);
        var writer = new CsvWriter(sw);

        IEnumerable records = reader.GetRecords<DataRecord>().ToList();

        List<CountAndFrequencyClass> list1 = new List<CountAndFrequencyClass>();
        list1 = CountAndFrequency(records, "ShipperName", 1);

        List<CountAndFrequencyClass> list2 = new List<CountAndFrequencyClass>();
        list2 = CountAndFrequency(records, "ShipperCity", 1);

        list1 = list1.Concat(list2).ToList();

        writer.WriteRecords(list2);
    }
}

The list1=list1.Concat(list2).ToList(); does indeed concatenate the strings, but it stacks them on top of each other when they're written out to the CSV file. I want to find a way to concatenate the lists horizontally (so they're displayed next to eachother) instead of vertically.

Thanks for any help and please let me know if additional information is needed!

I don't know if you care about efficiency, but it seems like it would be a lot more efficient to loop through the rows of the CSV one-by-one, rather than choosing a column, looping through all the rows, choosing another column, looping through all the rows, etc. — ProgrammingLlama, Jan 14 '20 at 02:09
Do you mean to say `append` a `list2` to `list1` and then write it as a single record to csv file — Prasad Telkikar, Jan 14 '20 at 02:22
You can merge the lists using [Zip](https://stackoverflow.com/questions/5122737/what-is-the-use-of-enumerable-zip-extension-method-in-linq), but how are you going to store the resulting list? You'll need a class that is capable of holding the data from both lists side by side, i.e. has twice as many properties as `CountAndFrequencyClass`. — John Wu, Jan 14 '20 at 02:29
@PrasadTelkikar, I have tried to use list1.AddRange(list2); to append the lists already, but this results in the same problem. The two lists are displayed vertically instead of horizontally. — jbove2, Jan 14 '20 at 02:30
@JohnWu That seems very promising. I'll use that in conjunction w/ ExpandoObject.Thanks a lot! — jbove2, Jan 14 '20 at 02:33

score 1 · Answer 1 · answered Jan 14 '20 at 07:36

1

You can use a loop to add list2 column to records of list1

foreach (var i=0 ; i< list1.Count; i++)
{
    if(i>=list2.Count ) break;
    var rec1 = list1[i];
    var rec2 = list2[i];
    rec1.NewColumn = rec2.ColumnToAdd;
}

answered Jan 14 '20 at 07:36

Ali Hamidi

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score 0 · Answer 2 · answered Jan 14 '20 at 14:03

You could write them to the file as you loop through the lists.

using (var sr = new StreamReader(inPath))
{
    using (var sw = new StreamWriter(outPath))
    {
        var reader = new CsvReader(sr);
        var writer = new CsvWriter(sw);

        IEnumerable records = reader.GetRecords<DataRecord>().ToList();

        List<CountAndFrequencyClass> list1 = new List<CountAndFrequencyClass>();
        list1 = CountAndFrequency(records, "ShipperName", 1);

        List<CountAndFrequencyClass> list2 = new List<CountAndFrequencyClass>();
        list2 = CountAndFrequency(records, "ShipperCity", 1);

        for (int i = 0; i < list1.Count; i++)
        {
            writer.WriteRecord(list1[i]);
            writer.WriteRecord(list2[i]);
            writer.NextRecord();
        }
    }
}

Concatenating lists horizontally C#

2 Answers2