Is there a best practice way to validate user input? [closed]

Answer 1

This is a simple requirement but sometimes being debated. This is my "current" approach how to deal with validation. I have not yet used this approach, and this is just a concept. This approach need to be developed more

First, create a custom validation attributes

public class ValidationAttribute : Attribute{
  public type RuleType{get;set;}
  public string Rule{get;set;}
  public string[] RuleValue{get;set;}
}

Second, create a custom error handler / message

public class ValidationResult{
  public bool IsSuccess{get;set;};
  public string[] ErrorMessages{get;set;};
}

Then create a validator

public class RuleValidator{
  public ValidationResult Validate(object o){
    ValidationResult result = new ValidationResult();
    List validationErrors = new List();
    PropertyInfo[] properties = o.GetType().GetProperties();
    foreach(PropertyInfo prop in properties){
      // validate here
      // if error occur{
        validationErrors.Add(string.Format("ErrorMessage at {0}", prop.Name));
      //}
    }

    result.ErrorMessages = validationErrors.ToArray();
  }
}

To use it, then you can do like this:

public class Person{
  [ValidationAttribute(typeof(string), "Required", "true")]
  public string Name{get;set;}

  [ValidationAttribute(typeof(int), "Min", "1")]
  public int Age{get;set;}
}

To call the validator

public void ValidatePerson(Person person){
  RuleValidator validator = new RuleValidator();
  ValidationResult result = validator.Validate(person);
  // generate the error message here, use result.ErrorMessages as source
}

What is the advantage:

1. You can use in any application platform (Winforms, Asp.Net, WCF, etc)
2. You can set the rule in attribute-level
3. It can do automated validation
4. This approach can be used with DependencyInjection with custom validators to separate validation logics

The disadvantage:

1. Hard to create the validators
2. If not handled well, the validators can become very large in number
3. Bad performance due to use of reflection