bitforum-backend/SharedKernel/Attributes/MaxFileSizeAttribute.cs

using Microsoft.AspNetCore.Http;
using System.Collections;
using System.ComponentModel.DataAnnotations;

namespace SharedKernel.Attributes
{
    /*
     * 파일 크기 제한
     */
    [AttributeUsage(AttributeTargets.Property)]
    public class MaxFileSizeAttribute : ValidationAttribute
    {
        private readonly long _maxKBytes;

        public MaxFileSizeAttribute(long maxKBytes)
        {
            _maxKBytes = maxKBytes;
        }

        public override bool IsValid(object? value)
        {
            if (value is IEnumerable files)
            {
                foreach (var obj in files)
                {
                    if (obj is IFormFile file && file.Length > _maxKBytes)
                    {
                        return false;
                    }
                }
            }

            return true;
        }

        public override string FormatErrorMessage(string name)
        {
            var template = string.IsNullOrWhiteSpace(ErrorMessage) ? "{0}의 크기는 최대 {1:N0}KB까지 허용됩니다." : ErrorMessage;

            return string.Format(template, name, _maxKBytes);
        }
    }
}