protected override ValidationResult IsValid(object value, ValidationContext validationContext) { if (value == null) { return(ValidationResult.Success); } IFormFile file = value as IFormFile; fileHelper = (IFileHelper)validationContext.GetService(typeof(IFileHelper)); bool IsImage = uploadedType == FileUploadedType.Image ? true : false; if (IsImage) { if (!fileHelper.CheckIfImageFile(file)) { return(new ValidationResult(FormatErrorMessage(validationContext.DisplayName))); } } else if (!mimeTypes.Contains(file?.ContentType)) { return(new ValidationResult(FormatErrorMessage(validationContext.DisplayName))); } return(ValidationResult.Success); }