Custom API ValidationAttribute for class property

Question

I have a class Student that contains the list of property 'TextPair' as shown below:

public class Student
{
    public List<TextPair> Hobbies { get; set; }
    public List<TextPair> Languages { get; set; }
    public List<TextPair> Majors { get; set; }

}

public class TextPair
{
    [StringLength(2, ErrorMessage = "The value length is invalid")]
    public string Value { get; set; }

    public string Text { get; set; }
}

Here, I validate the value for maximum length 2 using the StringLength AttributeValidator and decorate in the property 'Value' inside TextPair model. The problem for me is that the length is always fixed and length is always mandatory.

In my use case, I want the different flavor of Value in different part of the application (or, different property of same type) to support different lengths.

I was looking for something like below where I could pass the validation in my class where I declare my property 'TextPair' [i.e. I don't want to make the validation mandatory always and also not hard-code the value 2]

public class Student
{
    //Any length of the value is accepted for hobbies
    public List<TextPair> Hobbies{ get; set; }

    [ValuesLength(Length = 2, ErrorMessage = "Language code length must be 2 characters max")]
    public List<TextPair> Languages { get; set; }

    [ValuesLength(Length = 128, ErrorMessage = "The major should be within 128 characters length")]
    public List<TextPair> Majors{ get; set; }

}

Is there any efficient way to approach this solution?

Answer 1

One of the solution approached is as follows:

public class Student
{
    //Any length of the value is accepted for hobbies
    public List<TextPair> Hobbies{ get; set; }

    [ValuesLength(MaximumLength = 2, ErrorMessage = "Language code length must be 2 characters max")]
    public List<TextPair> Languages { get; set; }

    [ValuesLength(MaximumLength = 128, ErrorMessage = "The major should be within 128 characters length")]
    public List<TextPair> Majors{ get; set; }

}

My Custom Attribute validation is checking the list and verifying if anyone of the element values are exceeding the provided length as:

public class ValuesLengthAttribute : ValidationAttribute
    {
        public int MaximumLength { get; set; }
        public override Boolean IsValid(object value)
        {
            Boolean isValid = true;
            var list = value as List<TextPair>;
            if (list != null && list.Count>0)
                foreach (var item in list)
                {
                    if (item.Value.Length > MaximumLength)
                        isValid = false;
                }

            return isValid;
        }
    }