using System;

using System.Collections;

using Microsoft.Extensions.Options;

using System.ComponentModel.DataAnnotations;

​

public class ContainerApiOptions

{

    public int MaxUserDataLength { get; set; }  

}

​

public interface IInt32Accessor

{

    int GetValue();

}

​

public class MaxUserDataLengthConfigAccessor : IInt32Accessor

{

    private readonly ContainerApiOptions options;

​

    public MaxUserDataLengthConfigAccessor(IOptions<ContainerApiOptions> options)

    {

        this.options = options.Value;

    }

    public int GetValue()

    {

        return options.MaxUserDataLength;

    }

}

​

​

​

public class CustomMaxLengthAttribute : ValidationAttribute

{

    private readonly Type intAccessorType;

    public CustomMaxLengthAttribute(Type intAccessorType)

        : base()

    {

        this.intAccessorType = intAccessorType;

    }

    protected override ValidationResult? IsValid(object? value, ValidationContext validationContext)

    {

        var intAccessor = (IInt32Accessor)validationContext.GetService(intAccessorType);

        var maxLength = intAccessor.GetValue();

​

        if (value == null)

        {

            return ValidationResult.Success;

        }

        var length = value is string str

            ? str.Length

            : value is ICollection collection

            ? collection.Count

            : -1;

​

        if (length <= maxLength)

        {

            return ValidationResult.Success;

        }

        return new ValidationResult("oups");

    }

}

​

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

}