Read from .csv, calculate, write on .csv

Question

I am using csv reader for c#. This is my Record class

internal class Record
{
    int _y;
    int _x;
    [Name("y")]
    public int y { get; set; }
    [Name("x")]
    public int x { get; set; }
    
    public int getSum()
    {
        return _x+_y;
    }
}

Then, I try to read multiple .csv files and write aggregate to 1 .csv file

using (var writer = new StreamWriter(SaveTxt.Text))
            using (var csvOut = new CsvWriter(writer, CultureInfo.InvariantCulture))
            {
                for (int i = 0; i < Int16.Parse(numberFile); i++)
                {
                    using (var reader = new StreamReader(files[i]))
                    using (var csv = new CsvReader(reader, CultureInfo.InvariantCulture))
                    {
                        var records = csv.GetRecords<Record>();
                        csvOut.WriteRecords(records);
                        
                    }
                }
            }

But the result only show x and y data. Without showing result from getSum() function. What should I do to be able to manipulate the data that I read from .csv before write to other .csv ?

Caius Jard · Accepted Answer · 2020-07-24T06:02:47.117

I believe that CsvReader is writing X and Y because they are properties; it won't call methods and include their result in the file. Convert the getSum method to a property instead and it should appear in the file. You might also have to give it a name attribute. Here's a fixed up Record class:

internal class Record
{
    
    
    [Name("y")]
    public int X { get; set; }
    [Name("x")]
    public int Y { get; set; }

    [Optional]
    [Name("sum")]
    public int Sum { get { return X + Y; } set; } }
}

(Note that in c# we write properties and method names starting with a capital letter..)

I removed your _x and _y because they weren't doing anything; they weren't wired up to the x and y properties and would have always had their default value 0, so using them for sum would be 0 too

You ask how to manipulate the data before writing it; out some code between these two lines:

var records = csv.GetRecords<Record>();

//put code here

csvOut.WriteRecords(records);

Very great answer. But when I try to use your code. It shows `Header Validation Exception`. It cannot found header with name `sum`. How should I approach this issue? — irham dollah, Jul 24 '20 at 05:55
Oh.. it's looking for the column sum in the source file which I guess doesn't exist.. Check the edit I made; I believe if we mark Sum as optional it won't complain if it doesn't find it in the source file but will write it to the destination file — Caius Jard, Jul 24 '20 at 06:00

score 0 · Answer 2 · answered Jul 24 '20 at 05:39

The class Record should be the problem. GetSum() is a function and functions will be not serialized. x and y are properties (as you can indicate on { get; set; }) and will be serialized. You can change the function to a property like that:

public int GetSum
{
    get
    {
        return _x+_y;
    }
}

The next problem will be that the _x and _y variables are never set to a value. So GetSum will always return 0.

Read from .csv, calculate, write on .csv

2 Answers2