How to use FileHelper library to get number of delimiters

Question

Using the FileHelper Library Is there a way to get an exception if the record does not have expected number of delimiters in a line?

And another question is there is there a way to get an exception if a particular field for example Name is more than expected length?

If i set name to be maxLength 30 i get an exception if its is above 30.

Or a field is simply not equal to expected length?

Answer 1

get an exception if the record does not have expected number of delimiters in a line

It is the Default FileHelpers behavior to throw exceptions if there are not enough/too many fields in the line, so there is no need to do anything special to get it:

[DelimitedRecord(",")]
public class Test
{
    public int SomeInt { get; set; }
    public string SomeString { get; set; }
    public int SomeInt1 { get; set; }

    public override string ToString() =>
        $"{SomeInt} - {SomeString} - {SomeInt1}";
}


var result = new FileHelperEngine<Test>()
    .ReadString(@"123,That's the string")
    .Single();
Console.WriteLine(result);

Will result in

FileHelpers.FileHelpersException: Line: 1 Column: 4. Delimiter ',' not found after field 'k__BackingField' (the record has less fields, the delimiter is wrong or the next field must be marked as optional). at FileHelpers.DelimitedField.BasicExtractString(LineInfo line) at FileHelpers.DelimitedField.ExtractFieldString(LineInfo line) at FileHelpers.FieldBase.ExtractFieldValue(LineInfo line) at FileHelpers.RecordOperations.StringToRecord(Object record, LineInfo line, Object[] values) at FileHelpers.FileHelperEngine`1.ReadStreamAsList(TextReader reader, Int32 maxRecords, DataTable dt)

is there a way to get an exception if a particular field for example Name is more than expected length

As far as I can see FileHelpers doesn't support standard DataAnnotations out of the box (or it can actually support it but it doesn't work due to https://github.com/dotnet/standard/issues/450), so you will probably have to add validation manually

So, you install https://www.nuget.org/packages/System.ComponentModel.Annotations/4.4.0

And then by adding [StringLength(maximumLength: 5)] to the SomeString property on the model

[DelimitedRecord(",")]
public class Test
{
    public int SomeInt { get; set; }
    [StringLength(maximumLength: 5)]
    public string SomeString { get; set; }
    public int SomeInt1 { get; set; }

    public override string ToString() =>
        $"{SomeInt} - {SomeString} - {SomeInt1}";
}

With

var result = new FileHelperEngine<Test>()
    .ReadString(@"123,That's the string, 456")
    .Single();
Console.WriteLine(result);

var context = new ValidationContext(result, serviceProvider: null, items: null);
var results = new List<ValidationResult>();
var isValid = Validator.TryValidateObject(result, context, results, validateAllProperties: true);
if (!isValid)
{
    Console.WriteLine("Not valid");
    foreach (var validationResult in results)
    {
        Console.WriteLine(validationResult.ErrorMessage);
    }
} 

You will get the following output

Not valid

The field SomeString must be a string with a maximum length of 5.