How to parse CSV via CSV Helper to my custom class IFormFile .Net Core c#

Question

I'm uploading CSV file from client to .NET CORE Web Api app.

I'm using CsvHelper .net library.

I receive file successfully and I would like to parse it to my custom classes so I could loop throught the rows from csv.

But everytime I get Empty result like there are no rows.

I'm not sure what is wrong with my approach:

[HttpPost("import")]
public async Task<ActionResult> ImportData([FromForm] IFormFile file)
{

    using var memoryStream = new MemoryStream(new byte[file.Length]);
    await file.CopyToAsync(memoryStream);
    memoryStream.Position = 0;

    using (var reader = new StreamReader(memoryStream))
    using (var csvReader = new CsvReader(reader, System.Globalization.CultureInfo.InvariantCulture))
    {
        csvReader.Read();
        var records = csvReader.GetRecords<SiteDto>();
    }

    return Ok("ok");
}

This is how my CSV looks a like:

My Site Dto:

public class SiteDto
{
    public long Id { get; set; }
    public string Name { get; set; }
    public string Code { get; set; }
    public string CompanyName { get; set; }
    public string Location { get; set; }
}

And when I expand my result I saw something like warning about some headers?

@maytham-ɯɐɥʇʎɐɯ tried allready with try-catch. Does this have anything somewith with headers? Check for my edit please — Roxy'Pro
– Roxy'Pro, Commented Jan 18, 2021 at 22:33
Have you tried either changing the class property names or giving them manual Name attributes to match your csv file? — greenjaed
– greenjaed, Commented Jan 18, 2021 at 22:42
@maytham-ɯɐɥʇʎɐɯ That’s not how using var works - it gets disposed when it goes out of scope. — stuartd
– stuartd, Commented Jan 18, 2021 at 23:45
@stuartd sure agree, this is what happen when I comment late around sleeping time 😁 — Maytham Fahmi
– Maytham Fahmi, Commented Jan 19, 2021 at 7:53

Ahsan Ismail · Accepted Answer · 2022-02-17 09:38:17Z

I have created generic csv file converter to list of T type

public static class CSVParser
{
    
   
    public static DataTable ConvertCSVtoDataTable(IFormFile file)
    {
        DataTable dt = new DataTable();
        using (var stream = file.OpenReadStream())
        using (StreamReader sr = new StreamReader(stream))
        {
            string[] headers = sr.ReadLine().Split(',');
            foreach (string header in headers)
            {
                dt.Columns.Add(header);
            }
            while (!sr.EndOfStream)
            {
                string[] rows = sr.ReadLine().Split(',');
                DataRow dr = dt.NewRow();
                for (int i = 0; i < headers.Length; i++)
                {
                    dr[i] = rows[i];
                }
                dt.Rows.Add(dr);
            }

        }


        return dt;
    }
    public static List<T> ConvertDataTable<T>(DataTable dt)
    {
        List<T> data = new List<T>();
        foreach (DataRow row in dt.Rows)
        {
            T item = GetItem<T>(row);
            data.Add(item);
        }
        return data;
    }
    private static T GetItem<T>(DataRow dr)
    {
        Type temp = typeof(T);
        T obj = Activator.CreateInstance<T>();

        foreach (DataColumn column in dr.Table.Columns)
        {
            foreach (PropertyInfo pro in temp.GetProperties())
            {
                 

            if (pro.Name == column.ColumnName)
                {
                    var typeGEt = pro.PropertyType;
                    Type type = Nullable.GetUnderlyingType(pro.PropertyType) ?? pro.PropertyType;
                    string typeName = type.Name;

                   try
                    {
                        if (typeName == "Int16" || typeName == "Int32" || typeName == "Int64")
                        {
                            pro.SetValue(obj, Convert.ToInt32(dr[column.ColumnName]), null);

                        }
                        else if (typeName == "DateTime")
                        {

                            pro.SetValue(obj, DateTime.ParseExact((string)dr[column.ColumnName], "mm/dd/yyyy", CultureInfo.InvariantCulture), null);

                        }
                        else
                        {
                            pro.SetValue(obj, dr[column.ColumnName], null);

                        }
                    }

                    catch(Exception ex)
                    {
                        continue;

                    }



                }
                else
                    continue;
            }
        }
        return obj;
    }


    public static IEnumerable<T> toList<T>(this DataTable? dt)
    {
        List<T> data = new List<T>();
        foreach (DataRow row in dt.Rows)
        {
            T item = GetItem<T>(row);
            data.Add(item);
        }
        return data;
    }

    public static string getExtension(this string name)
    {
       return Path.GetExtension(name);
        
    }
    public static IEnumerable<T> CSVToList<T>(this IFormFile? file)
    {
        if (file != null)
        {
             if (file.FileName.getExtension() != ".csv")
                throw new Exception("File is not valid CSV");
            else
                return ConvertCSVtoDataTable(file).toList<T>();

        }
        else
            throw new Exception("File can not be empty");
    }
 }

To use this

postedFile.CSVToList<TypeModal>();

postedFile is IFormFile and TypeModal is Entity

Hi Ahsan Ismail, whilst you answer provides a possible solution to reading CSV files in general. I'm not sure that it actually answers the original question which is about how to use the CsvHelper .NET library to read a CSV.

David Specht · Accepted Answer · 2021-01-19 05:47:43Z

https://joshclose.github.io/CsvHelper/getting-started

The GetRecords method will return an IEnumerable that will yield records. What this means is that only a single record is returned at a time as you iterate the records.

Try calling ToList() to iterate the records and remove csvReader.Read();. GetRecords() calls Read() internally. Using both is causing CsvReader to skip the header row.

using (var reader = new StreamReader(memoryStream))
using (var csvReader = new CsvReader(reader, System.Globalization.CultureInfo.InvariantCulture))
{
    var records = csvReader.GetRecords<SiteDto>().ToList();
}

Also add a name attribute to your class, so that CsvHelper knows how to map the Id property.

public class SiteDto
{
    [Name("SiteId")]
    public long Id { get; set; }
    public string Name { get; set; }
    public string Code { get; set; }
    public string CompanyName { get; set; }
    public string Location { get; set; }
}

Tyler2P · Accepted Answer · 2023-06-05 15:34:16Z

1

public List<organizations> ReadCSVFile([FromForm] UploadFile location)
{
  try
  {
    using var memoryStream = new MemoryStream(new byte[location.Files.Length]);
    location.Files.CopyToAsync(memoryStream);
    memoryStream.Position = 0;
    using (var reader = new StreamReader(memoryStream))
    using (var csvReader = new CsvReader(reader, CultureInfo.InvariantCulture))
    {
      csvReader.Context.RegisterClassMap<organizationsMap>();
      var records = csvReader.GetRecords<organizations>().ToList();
      return records;
    }
  }
  catch (Exception e)
  {
    throw e;
  }
  return null;
}

edited Jun 5, 2023 at 15:34

Tyler2P

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answered Jun 5, 2023 at 12:31

Pramod Kumar

213 bronze badges

2 Comments

Pramod Kumar Over a year ago

you can try above it's a running code

Tyler2P Over a year ago

Your answer could be improved by adding more information on what the code does and how it helps the OP.

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