C#•3mo ago

How to add additional headers/columns to CSV file?

Using CSVHelper to manipulate a CSV file but when I try to add additional columns of information I get the error, I thought this would be really simple to add.

Error: Header with name 'Payee_Country'[0] was not found.
Header with name 'Payer_Address1'[0] was not found.
Header with name 'Payer_Address2'[0] was not found.
Header with name 'Payer_City'[0] was not found.
Header with name 'Payer_State' [0] was not found.
Header with name 'Payer_Zip'[0] was not found.
Header with name 'Payer_Country'[0] was not found.

code.txt

9 Replies

Pobiega•3mo ago

CSVHelper doesnt by default allow missing headers but if you create a config and set it up correctly, it allows it just fine

var config = new CsvConfiguration(CultureInfo.InvariantCulture) { HeaderValidated = null, MissingFieldFound = null };

using (var reader = new StreamReader("data.csv"))
using (var csv = new CsvReader(reader, config))
{
    list = csv.GetRecords<T>().ToList();
}

var config = new CsvConfiguration(CultureInfo.InvariantCulture) { HeaderValidated = null, MissingFieldFound = null };

using (var reader = new StreamReader("data.csv"))
using (var csv = new CsvReader(reader, config))
{
    list = csv.GetRecords<T>().ToList();
}

note how I set both HeaderValidated and MissingFieldFound to null here this allows me to parse a file that doesnt match my record class. HOWEVER this is a bad idea If you know the CSV file doesnt contain these values and you want to add them, you should have two models one without and one with the new fields then simply read the values, then use .Select or some other method to turn your objects from A into B, adding the data as needed, then save the list of Bs

SCOLANATOR•3mo ago

Could you show me how to do that? I'm struggling a bit here

Pobiega•3mo ago

List<OriginalRecord> list;

var config = new CsvConfiguration(CultureInfo.InvariantCulture) { HeaderValidated = null, MissingFieldFound = null };

using (var reader = new StreamReader("data.csv"))
using (var csv = new CsvReader(reader, config))
{
    list = csv.GetRecords<OriginalRecord>().ToList();
}

var newList = list.Select(x => new UpdatedRecord()
{
    Id = x.Id, Name = x.Name, Time = x.Time, RandomNumber = Random.Shared.Next(100),
}).ToList();

// newList now contains the updated list

List<OriginalRecord> list;

var config = new CsvConfiguration(CultureInfo.InvariantCulture) { HeaderValidated = null, MissingFieldFound = null };

using (var reader = new StreamReader("data.csv"))
using (var csv = new CsvReader(reader, config))
{
    list = csv.GetRecords<OriginalRecord>().ToList();
}

var newList = list.Select(x => new UpdatedRecord()
{
    Id = x.Id, Name = x.Name, Time = x.Time, RandomNumber = Random.Shared.Next(100),
}).ToList();

// newList now contains the updated list

SCOLANATOR•3mo ago

Thank you, I'm not quite sure how to add this into my code but I'll give it a go!

Pobiega•3mo ago

step 1 is to just make a record type that has only the headers and values that are in your current csv file then you make the second record type that has the ones you want in your output then its as simple as making a method that converts from type 1 into type 2, passing that method to .Select (I used a lambda, but you can pass a real method too) and you're pretty much done

SCOLANATOR•3mo ago

Could you help me put this into my code? I'm banging my head trying to do this, it's been a while since I was last working on C# and this code

Pobiega•3mo ago

This is very basic stuff, except maybe the .Select call but I can help you with that have you made the two models and the mapping method? @SCOLANATOR ?

SCOLANATOR•3mo ago

@Pobiega Sorry for the delayed response, had something come up. This was what i've put together so far but there's an issue with line 188

SCOLANATOR•3mo ago

code.txt

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How to add additional headers/columns to CSV file?