Create custom DataType Validation

Question

I want to make my own validation class (i have a lot of validation methods in JS that i want to translate into C# to use with MVC models) that works exactly like data annotations do, validating in client and server side: [DataType(MyDataType)] or like a Validation DataAnnotation Attribute like this: [MyDataTypeValidation]

i don't know wich option is better to make my validation "library"

In example i have my class FigurasDA and i want to make my custom validation to the attribute nombre.

namespace MonitoreoIntegrado.Models
{
    [MetadataType(typeof(FigurasDA))]
    public partial class Figuras
{
}

public class FigurasDA
{
    [DataType(MyDataType)]
    //or
    [MyDataTypeValidation]
    public string nombre { get; set; }
}
}

so in this case, i want to validate that the string matches the regexp @"^[\w\s\.\-_]+$" and shows a error message like this "Solo se permite letras, numeros y puntuaciones(- _ .)" if don't. (this is my "Alfanumerico" datatype).

Can you give me an example where to put my validation class and what code write inside?.

Answer 1

Actually it's easy... You just have to inherit you custom validation attribute from ValidationAttribute class and provide your own IsValid logic. For example:

public class MyDataTypeValidationAttribute : ValidationAttribute
{
    private Regex _regex = new Regex(@"^[\w\s.-_]+$");          

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {               
        if (_regex.IsMatch(value.ToString()))
        {
            return ValidationResult.Success;
        }

        return new ValidationResult("Solo se permite letras, numeros y puntuaciones(- _ .)" );
    }
}

and in your view model you can use:

public class FigurasDA
{    
    [MyDataTypeValidation]
    public string nombre { get; set; }
}

You can save this validation attribute, for example in Attributes folder in your MVC project: