如何在ASP.NET MVC 6中继续使用ModelState和RedirectToAction？

Question

我有一个删除对象的方法。 删除不属于视图，并且是“EditReport”中的“删除”按钮。 成功删除“报告”上的重定向后。

[HttpPost]
[Route("{reportId:int}")]
[ValidateAntiForgeryToken]
public IActionResult DeleteReport(int reportId)
{
    var success = _reportService.DeleteReportControl(reportId);
    if (success == false)
    {
        ModelState.AddModelError("Error", "Messages");
        return RedirectToAction("EditReport");
    }
    ModelState.AddModelError("OK", "Messages");
    return RedirectToAction("Report");
}

在ASP.NET MVC 5中，我使用以下属性在方法之间保存ModelState。 我从这里开始： https ： //stackoverflow.com/a/12024227/3878213

public class SetTempDataModelStateAttribute : ActionFilterAttribute
{
    public override void OnActionExecuted(ActionExecutedContext filterContext)
    {
        base.OnActionExecuted(filterContext);         
        filterContext.Controller.TempData["ModelState"] = 
           filterContext.Controller.ViewData.ModelState;
    }
}

public class RestoreModelStateFromTempDataAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        base.OnActionExecuting(filterContext);
        if (filterContext.Controller.TempData.ContainsKey("ModelState"))
        {
            filterContext.Controller.ViewData.ModelState.Merge(
                (ModelStateDictionary)filterContext.Controller.TempData["ModelState"]);
        }
    }
}

但是在ASP.NET MVC 6 RC 1（ASP.NET Core 1.0）中，此代码不起作用。

filterContext.Controller中的错误不包含TempData和ViewData的定义。

Answer 1

感谢回答 ，我意识到需要创建自己的代码ASP.NET Core 1.0（完整的.NET Framework 4.6.2）

public class SetTempDataModelStateAttribute : ActionFilterAttribute
{
    public override void OnActionExecuted(ActionExecutedContext filterContext)
    {
        base.OnActionExecuted(filterContext);

        var controller = filterContext.Controller as Controller;
        var modelState = controller?.ViewData.ModelState;
        if (modelState != null)
        {
            var listError = modelState.Where(x => x.Value.Errors.Any())
                .ToDictionary(m => m.Key, m => m.Value.Errors
                .Select(s => s.ErrorMessage)
                .FirstOrDefault(s => s != null));
            controller.TempData["ModelState"] = JsonConvert.SerializeObject(listError);
        }
    }
}
public class RestoreModelStateFromTempDataAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        base.OnActionExecuting(filterContext);

        var controller = filterContext.Controller as Controller;
        var tempData = controller?.TempData?.Keys;
        if (controller != null && tempData != null)
        {
            if (tempData.Contains("ModelState"))
            {
                var modelStateString = controller.TempData["ModelState"].ToString();
                var listError = JsonConvert.DeserializeObject<Dictionary<string, string>>(modelStateString);
                var modelState = new ModelStateDictionary();
                foreach (var item in listError)
                {
                    modelState.AddModelError(item.Key, item.Value ?? "");
                }

                controller.ViewData.ModelState.Merge(modelState);
            }
        }
    }
}

代码的非同步版本ASP.NET Core 1.0（完整的.NET Framework 4.6.2）

public class SetTempDataModelStateAttribute : ActionFilterAttribute
    {
        public override async Task OnActionExecutionAsync(ActionExecutingContext filterContext, ActionExecutionDelegate next)
        {
            await base.OnActionExecutionAsync(filterContext, next);

            var controller = filterContext.Controller as Controller;
            var modelState = controller?.ViewData.ModelState;
            if (modelState != null)
            {
                var listError = modelState.Where(x => x.Value.Errors.Any())
                    .ToDictionary(m => m.Key, m => m.Value.Errors
                    .Select(s => s.ErrorMessage)
                    .FirstOrDefault(s => s != null));
                var listErrorJson = await Task.Run(() => JsonConvert.SerializeObject(listError));
                controller.TempData["ModelState"] = listErrorJson;
            }
            await next();
        }
    }
public class RestoreModelStateFromTempDataAttribute : ActionFilterAttribute
    {
        public override async Task OnActionExecutionAsync(ActionExecutingContext filterContext, ActionExecutionDelegate next)
        {
            await base.OnActionExecutionAsync(filterContext, next);

            var controller = filterContext.Controller as Controller;
            var tempData = controller?.TempData?.Keys;
            if (controller != null && tempData != null)
            {
                if (tempData.Contains("ModelState"))
                {
                    var modelStateString = controller.TempData["ModelState"].ToString();
                    var listError = await Task.Run(() => 
                        JsonConvert.DeserializeObject<Dictionary<string, string>>(modelStateString));
                    var modelState = new ModelStateDictionary();
                    foreach (var item in listError)
                    {
                        modelState.AddModelError(item.Key, item.Value ?? "");
                    }

                    controller.ViewData.ModelState.Merge(modelState);
                }
            }
            await next();
        }
    }

Answer 2

编译代码的修复程序如下所示，但似乎ASP.NET Core不支持序列化模型状态（由于ModelStateEntry包含永远不可序列化的异常）。

因此，您无法在TempData序列化模型状态。 正如本GitHub问题所解释的那样，似乎没有计划改变这种行为。

---

ActionExecutingContext的Controller属性是object类型。 这是因为ASP.NET Core中的Controller不需要从Controller继承，因此它们没有共同的基类型。

要访问TempData属性，必须TempData其TempData为Controller 。 您的属性可能如下所示：

public class SetTempDataModelStateAttribute : ActionFilterAttribute
{
    public override void OnActionExecuted(ActionExecutedContext filterContext)
    {
        base.OnActionExecuted(filterContext);

        Controller controller = filterContext.Controller as Controller;
        if (controller != null)
        {
            controller.TempData["ModelState"] = controller.ViewData.ModelState;
        }
    }
}

public class RestoreModelStateFromTempDataAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        base.OnActionExecuting(filterContext);

        Controller controller = filterContext.Controller as Controller;
        if (controller != null & controller.TempData.ContainsKey("ModelState"))
        {
            controller.ViewData.ModelState.Merge(
                (ModelStateDictionary)controller.TempData["ModelState"]);
        }
    }
}