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Unable to write from List<string[]> to csv file #2302

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casualsailo opened this issue Nov 17, 2024 · 3 comments
Open

Unable to write from List<string[]> to csv file #2302

casualsailo opened this issue Nov 17, 2024 · 3 comments
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@casualsailo
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Hi,

I am using CsvHelper 33.0.1

I have a list of string arrays that I want to write to a csv file, but I keep getting an error on csv.WriteRecords() or csv.WriteRecord()

CsvHelper.Configuration.ConfigurationException
HResult=0x80131500
Message=Types that inherit IEnumerable cannot be auto mapped. Did you accidentally call GetRecord or WriteRecord which acts on a single record instead of calling GetRecords or WriteRecords which acts on a list of records?
Source=CsvHelper
StackTrace:
at CsvHelper.Configuration.ClassMap.AutoMap(CsvContext context)
at CsvHelper.CsvContext.AutoMap(Type type)
at CsvHelper.CsvWriter.WriteHeader(Type type)
at CsvHelper.CsvWriter.WriteHeaderFromTypeT
at CsvHelper.CsvWriter.WriteRecords[T](IEnumerable`1 records)

This is an example of what I am doing:

void Main()
{
    var input = new List<string[]>()
    {
        new string[] { "a1", "a2" },
        new string[] { "b1", "b2" },
        new string[] { "c1", "c2" }
    };

    using (var writer = new StreamWriter(outputFile))
    using (var csv = new CsvWriter(writer, CultureInfo.InvariantCulture))
    {
        csv.WriteRecords(input);
    }
}

I've also tried

using (var writer = new StreamWriter(outputFile))
using (var csv = new CsvWriter(writer, CultureInfo.InvariantCulture))
{
    foreach (var row in input)
    {
        csv.WriteRecord(row);
    }
}

Am I using WriteRecord()/WriteRecords() incorrectly? Thanks

@AltruCoder
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CsvHelper is expecting an object with members to map rather than an array of strings. I believe the only way to do it would be to have CsvHelper write out the individual fields.
See #765

void Main()
{
  var input = new List<string[]>()
  {
    new string[] { "a1", "a2" },
    new string[] { "b1", "b2" },
    new string[] { "c1", "c2" }
  };
  
  //using (var writer = new StreamWriter(Console.Out))
  using (var csv = new CsvWriter(Console.Out, CultureInfo.InvariantCulture))
  {
    foreach (var row in input)
    {
      foreach (var item in row)
      {
         csv.WriteField(item);
      }
      csv.NextRecord();
    }
  }	
}

@casualsailo
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Thanks!

Contrary to what the name implies, it seems to works with string[], and doesn't require string

using (var writer = new StreamWriter(outputFile))
using (var csv = new CsvWriter(writer, CultureInfo.InvariantCulture))
{
    foreach (var row in input)
    {
        csv.WriteField(row);
    }
}

@AltruCoder
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Good to know! You do still need the csv.NextRecord().

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