input-validators.md

Input validators

Input validator is just a delegate

• Executing one or more validators
• Encapsulating generic and validation strategy calls
• Merging multiple ValidationResult into one

public delegate ValueTask<ValidationResult?> InputValidator(object argument, CancellationToken cancellationToken);

By default all InputValidator implementations is here ValidationDefaults.InputValidators

It is a set of factories with predefined validation scenarios

Writing custom input validator

Like other parts of this library, you can write your own factory to create InputValidator

public static InputValidator CreateCustomInputValidator()
{
  return context =>
  {
    // Now you need to validate `argument` somehow and return ValidationResult
    return ...;
  }
}

Custom input validator usage

# global
services.AddGraphQL()
  .AddFluentValidation(options =>
  {
    options.UseInputValidators(CreateCustomInputValidator());
  });

# field
descriptor.Field(x => x.Example(default!))
  .Argument("input", argument => argument.UseFluentValidation(options =>
  {
    options.UseInputValidators(CreateCustomInputValidator())
  }));