AoK.FluentValidation 1.9.0

About

AoK.FluentValidation addresses the issue of high cyclomatic complexity that arises from validations (parameters or otherwise) that are peformed as fail-fast before performing the function. In case of parameter validations, the cyclomatic complexity would become minimally (n + 1), where n is the number of parameters to be validated. AoK.FluentValidation, apart from helping you to write validation code fluently, reduces the complexity of such code to 2 irrespective of the number of parameters to be validated.

Usage

// Conventional
void ValidateParameters(SomeClass obj, int percent, string message)
{    
    if(obj == null)
    {
        // print error
        return;
    }

    if(percent < 0 || percent > 100)            // Cyclomatic complexity >= 4
    {
        // print error
        return;
    }

    if(string.IsNullorEmpty(message))
    {
        // print error
        return;
    }
}

// AoK.FluentValidation
void ValidateParameters(SomeClass obj, int percent, string message)
{    
    IValidator validator =
        ValidatorBuilder
            .WithValidation(() => obj != null)
            .AndFailureMessage($"{nameof(obj)} cannot be null")
            .AndWithValidation(() => percent >= 0 && percent <= 100)
            .AndFailureMessage($"{nameof(percent)} shall be in range 0..100")     // cyclomatic complexity <= 3
            .AndWithValidation(() => !string.IsNullorEmpty(message))
            .AndFailureMessage($"{nameof(message)} shall not be null or empty")
            .Build();
    
    // validation
    if(!validator.IsValid())
    {
        // print validator.Error
        return;
    }
}

Remarks

1. Validator throws InvalidOperationException when validator.Error is called before validator.IsValid()
2. Passing null validation will result in validation always passing