DataAnnotations MaxLength and StringLength for string[] or List<string>?

Question

I am trying to figure out if there is a proper way to achieve this with DataAnnotations:

Have an array or List of strings where the maximum number of elements in the array or List is 2 items and where each string may only be, say 255 characters long. Will this work:

[MaxLength(2)]
[StringLength(255)]
public string[] StreetAddress { get; set; }

I would rather not have to make a new class just to hold a string Value property to constrain each string to 255 characters.

Answer 1

You can create your own validation attribute by inheriting from Validation Attribute like described here: How to: Customize Data Field Validation in the Data Model Using Custom Attributes

Answer 2

This is a custom attribute for list of strings:

public class StringLengthListAttribute : StringLengthAttribute
{
    public StringLengthListAttribute(int maximumLength)
        : base(maximumLength) { }

    public override bool IsValid(object value)
    {
        if (value is not List<string>)
            return false;

        foreach (var str in value as List<string>)
        {
            if (str.Length > MaximumLength || str.Length < MinimumLength)
                return false;
        }

        return true;
    }
}