How can I retrieve data from multiple objects from a .csv file using CsvHelper?

Question

I have a list with type MyClass, and MyClass has several attributes. How can i retrieve data using CsvHelper, if .csv file looks like this? (Yes, attributes of type Data1 are numbered.)

Date       |   Data1  | Unit  |   Data2  | Unit  |   Data3  | Unit  | ... | DataN    |   Unit 
-----------|----------|-------|----------|-------|----------|-------|-----|----------|----------
2020.01.02 |     1    |   kW  |     3    |  kW   |    1.5   |  kW   | ... |     0    |    kW
2020.01.03 |     0    |   kW  |     4    |  kW   |     1    |  kW   | ... |     3    |    kW
2020.01.04 |     4    |   kW  |     2    |  kW   |     1    |  kW   | ... |     2    |    kW

This is what i want to see. The objects are stored in a list that can store MyClass type.


    List(MyClass) = [Object-1, Object-1, Object-3, ..., Object-N]

Object-1: [(2020.01.02.,1, kW),(2020.01.03.,0, kW),,(2020.01.04.,4, kW)]
Object-2: [(2020.01.02.,3, kW),(2020.01.03.,4, kW),,(2020.01.04.,2, kW)]
Object-3: [(2020.01.02.,1.5, kW),(2020.01.03.,1, kW),,(2020.01.04.,1, kW)]
...
Object-N: [(2020.01.02.,0, kW),(2020.01.03.,3, kW),,(2020.01.04.,2, kW)]



    MappedClass{
        private DateTime Date;
        private List List;
    }



    MyClass{
        private DateTime Date;
        private string A1; //Attribute1
        private int A2; //Attribute2
    }

If the properties of only one object are listed, then i can do the task, but not with multiple objects and this layout. I thought of reading the file row by row and then somehow pairing its related data.

How to do this task effectively?

Hi @Krsztn_, welcome to Stackoverflow! Could you please edit your question to include a few rows from your CSV file? It's not very clear to me how your CSV looks like from your question. Also, what is MappedClass and how do you want to use it? — hbot

David Specht David Specht · Accepted Answer · 2020-04-14T16:09:22

This would be one way to do it.

public class Program
{
    public static void Main(string[] args)
    {
        using (MemoryStream stream = new MemoryStream())
        using (StreamWriter writer = new StreamWriter(stream))
        using (StreamReader reader = new StreamReader(stream))
        using (CsvReader csv = new CsvReader(reader, CultureInfo.InvariantCulture))
        {
            writer.WriteLine("Date,Data1,Unit,Data2,Unit,Data3,Unit");
            writer.WriteLine("2020.01.02,1,kw,3,kw,1.5,kw");
            writer.WriteLine("2020.01.03,0,kw,4,kw,1,kw");
            writer.Flush();
            stream.Position = 0;

            var records = new List<MappedClass>();

            csv.Read();
            csv.ReadHeader();

            while (csv.Read())
            {
                var record = new MappedClass
                {
                    Date = record.Date,
                    Date = csv.GetField<DateTime>(0),
                    List = new List<MyClass>()
                };

                for (int i = 1; i < csv.Context.HeaderRecord.Length; i += 2)
                {
                    var item = new MyClass
                    {
                        Data = csv.GetField<decimal>(i),
                        Unit = csv.GetField<string>(i + 1)
                    };

                    record.List.Add(item);
                }

                records.Add(record);
            }
        }
    }
}

public class MappedClass
{
    public DateTime Date { get; set; }
    public List<MyClass> List { get; set; }
}

public class MyClass {
    public DateTime Date;
    public string Unit; //Attribute1
    public decimal Data; //Attribute2
}

How can I retrieve data from multiple objects from a .csv file using CsvHelper?

1 Answers