/// <summary> /// Executes custom server side validation for the model /// </summary> /// <param name="validationContext"></param> /// <returns></returns> public IEnumerable <ValidationResult> Validate(ValidationContext validationContext) { if (PreValueModel.IsRequired && Value.IsNullValueOrEmpty() && !ContentExtensions.HasFile(NewFile)) { yield return(new ValidationResult("Value is required", new[] { "Value" })); } }