Add validation to CsvHelper.Configuration.ClassMap object (string)

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I use CsvHelper.Configuration.ClassMap to read csv file and faced with data validation.

I found Validate option and wrote a simple code:

Map(m => m.Field).Name("myField").Validate(row => row.Contains('='));

But I don't understand an output and confused a bit with possible options.

So, my questions are:

  1. If it returns true - will I receive string? Or boolean true? I want to add the value to DB after that..

  2. If it returns false - what I receive? And, anyway, the value will not be added to DB?

  3. Any ideas how to add simple validation? Usual code, without validation:

    Map(m => m.Field).Name("myField");

Thank you in advance!

csvhelper csv c#
1 Answers

You would write it this way using CsvHelper 27.1.1

Map(m => m.Field).Name("myField").Validate(x => x.Field.Contains('='));

In 15.0.3 you would not use Field

Map(m => m.Field).Name("myField").Validate(x => x.Contains("="));

The Validate function has the following signature :

public virtual MemberMap<TClass, TMember> Validate(Validate validateExpression);

The Validate Type is a delegate which is declared this way :

public delegate bool Validate(ValidateArgs args);

ValidateArgs has the property Field which i use in my code sample.

It will throw a FieldValidationException if the condition is false during the conversion.

You could catch this exception and add some logic.

  1. if true the conversion will work as expected you field will be mapped.
  2. A FieldValidationException will be thrown.
  3. See code above.
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