我实现了对"在RedirectToAction中保留ModelState错误?"问题的第二个响应,该问题涉及使用两个自定义ActionFilterAttributes。我喜欢这个解决方案,它只需为需要功能的方法添加一个属性,就可以保持代码的整洁。
该解决方案在大多数情况下都能很好地工作,但我遇到了一个重复部分视图的问题。基本上,我有一个部分视图,它使用自己的模型,与父视图使用的模型分离。
我的代码的简化版本从主视图:
@for (int i = 0; i < Model.Addresses.Count; i++)
{
address = (Address)Model.Addresses[i];
@Html.Partial("_AddressModal", address);
}
局部视图"_AddressModal":
@model Acme.Domain.Models.Address
[...]
@Html.TextBoxFor(model => model.Address1, new { @class = "form-control" } )
[...]
当不使用自定义ActionFilterAttributes时,一切都按预期进行。每次执行Partial View时,lamba表达式(如"model=>model.Address1")都会从ModelState中提取正确的值。
问题是当我获得重定向并使用了自定义ActionFilterAttributes时。核心问题是,不仅更新了Address的一个实例的ModelState,而且部分视图生成的所有Address的ModelState都被覆盖,因此它们包含相同的值,而不是正确的实例值。
我的问题是如何修改自定义ActionFilterAttributes,使其仅更新一个受影响Address实例的ModelState,而不是所有ModelState?我希望避免向使用该属性的方法添加任何内容,以保持干净的实现。
以下是来自另一个问题的自定义ActionFilterAttributes代码:
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"]);
}
}
}
检查此实现(ben-forst)是否有效:我用得很重,从来没有遇到过问题。
您是否正确设置了属性?'RestoreModelStateFromTempDataAttribute
在get
操作上,SetTempDataModelState
在您的post
操作上?
以下是所需的4个类(导出、导入、传输和验证)ModelState
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public class ExportModelStateToTempDataAttribute : ModelStateTempDataTransfer
{
public override void OnActionExecuted(ActionExecutedContext filterContext)
{
// Only copy when ModelState is invalid and we're performing a Redirect (i.e. PRG)
if (!filterContext.Controller.ViewData.ModelState.IsValid &&
(filterContext.Result is RedirectResult || filterContext.Result is RedirectToRouteResult))
{
ExportModelStateToTempData(filterContext);
}
base.OnActionExecuted(filterContext);
}
}
/// <summary>
/// An Action Filter for importing ModelState from TempData.
/// You need to decorate your GET actions with this when using the <see cref="ValidateModelStateAttribute"/>.
/// </summary>
/// <remarks>
/// Useful when following the PRG (Post, Redirect, Get) pattern.
/// </remarks>
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public class ImportModelStateFromTempDataAttribute : ModelStateTempDataTransfer
{
public override void OnActionExecuted(ActionExecutedContext filterContext)
{
// Only copy from TempData if we are rendering a View/Partial
if (filterContext.Result is ViewResult)
{
ImportModelStateFromTempData(filterContext);
}
else
{
// remove it
RemoveModelStateFromTempData(filterContext);
}
base.OnActionExecuted(filterContext);
}
}
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public abstract class ModelStateTempDataTransfer : ActionFilterAttribute
{
protected static readonly string Key = typeof(ModelStateTempDataTransfer).FullName;
/// <summary>
/// Exports the current ModelState to TempData (available on the next request).
/// </summary>
protected static void ExportModelStateToTempData(ControllerContext context)
{
context.Controller.TempData[Key] = context.Controller.ViewData.ModelState;
}
/// <summary>
/// Populates the current ModelState with the values in TempData
/// </summary>
protected static void ImportModelStateFromTempData(ControllerContext context)
{
var prevModelState = context.Controller.TempData[Key] as ModelStateDictionary;
context.Controller.ViewData.ModelState.Merge(prevModelState);
}
/// <summary>
/// Removes ModelState from TempData
/// </summary>
protected static void RemoveModelStateFromTempData(ControllerContext context)
{
context.Controller.TempData[Key] = null;
}
}
/// <summary>
/// An ActionFilter for automatically validating ModelState before a controller action is executed.
/// Performs a Redirect if ModelState is invalid. Assumes the <see cref="ImportModelStateFromTempDataAttribute"/> is used on the GET action.
/// </summary>
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public class ValidateModelStateAttribute : ModelStateTempDataTransfer
{
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
if (!filterContext.Controller.ViewData.ModelState.IsValid)
{
if (filterContext.HttpContext.Request.IsAjaxRequest())
{
ProcessAjax(filterContext);
}
else
{
ProcessNormal(filterContext);
}
}
base.OnActionExecuting(filterContext);
}
protected virtual void ProcessNormal(ActionExecutingContext filterContext)
{
// Export ModelState to TempData so it's available on next request
ExportModelStateToTempData(filterContext);
// redirect back to GET action
filterContext.Result = new RedirectToRouteResult(filterContext.RouteData.Values);
}
protected virtual void ProcessAjax(ActionExecutingContext filterContext)
{
var errors = filterContext.Controller.ViewData.ModelState.ToSerializableDictionary();
var json = new JavaScriptSerializer().Serialize(errors);
// send 400 status code (Bad Request)
filterContext.Result = new HttpStatusCodeResult((int)HttpStatusCode.BadRequest, json);
}
}
编辑
这是一个正常的(非作用滤波器)PRG模式:
[HttpGet]
public async Task<ActionResult> Edit(Guid id)
{
var calendarEvent = await calendarService.FindByIdAsync(id);
if (calendarEvent == null) return this.RedirectToAction<CalendarController>(c => c.Index());
var model = new CalendarEditViewModel(calendarEvent);
ViewData.Model = model;
return View();
}
[HttpPost]
public async Task<ActionResult> Edit(Guid id, CalendarEventBindingModel binding)
{
if (!ModelState.IsValid) return await Edit(id);
var calendarEvent = await calendarService.FindByIdAsync(id);
if (calendarEvent != null)
{
CalendarEvent model = calendarService.Update(calendarEvent, binding);
await context.SaveChangesAsync();
}
return this.RedirectToAction<CalendarController>(c => c.Index());
}
使用操作筛选器(或其目的),您希望避免的是删除ModelState.is对每个操作后进行有效检查,因此(使用操作筛选器)相同:
[HttpGet, ImportModelStateFromTempData]
public async Task<ActionResult> Edit(Guid id)
{
var calendarEvent = await calendarService.FindByIdAsync(id);
if (calendarEvent == null) return this.RedirectToAction<CalendarController>(c => c.Index());
var model = new CalendarEditViewModel(calendarEvent);
ViewData.Model = model;
return View();
}
// ActionResult changed to RedirectToRouteResult
[HttpPost, ValidateModelState]
public async Task<RedirectToRouteResult> Edit(Guid id, CalendarEventBindingModel binding)
{
// removed ModelState.IsValid check
var calendarEvent = await calendarService.FindByIdAsync(id);
if (calendarEvent != null)
{
CalendarEvent model = calendarService.Update(calendarEvent, binding);
await context.SaveChangesAsync();
}
return this.RedirectToAction<CalendarController>(c => c.Index());
}
这里没有更多的事情发生。因此,如果你只使用ExportModelState操作过滤器,你会得到这样的后操作:
[HttpPost, ExportModelStateToTempData]
public async Task<RedirectToRouteResult> Edit(Guid id, CalendarEventBindingModel binding)
{
if (!ModelState.IsValid) return RedirectToAction("Edit", new { id });
var calendarEvent = await calendarService.FindByIdAsync(id);
if (calendarEvent != null)
{
CalendarEvent model = calendarService.Update(calendarEvent, binding);
await context.SaveChangesAsync();
}
return this.RedirectToAction<CalendarController>(c => c.Index());
}
这让我问你,你为什么一开始就为ActionFilters
而烦恼?虽然我确实喜欢ValidateModelState模式(很多人不喜欢),但如果你在控制器中重定向,我真的看不到任何好处,除了一种情况,你有额外的模型状态错误,为了完整起见,让我给你举一个例子:
[HttpPost, ValidateModelState, ExportModelStateToTempData]
public async Task<RedirectToRouteResult> Edit(Guid id, CalendarEventBindingModel binding)
{
var calendarEvent = await calendarService.FindByIdAsync(id);
if (!(calendarEvent.DateStart > DateTime.UtcNow.AddDays(7))
&& binding.DateStart != calendarEvent.DateStart)
{
ModelState.AddModelError("id", "Sorry, Date start cannot be updated with less than 7 days of event.");
return RedirectToAction("Edit", new { id });
}
if (calendarEvent != null)
{
CalendarEvent model = calendarService.Update(calendarEvent, binding);
await context.SaveChangesAsync();
}
return this.RedirectToAction<CalendarController>(c => c.Index());
}
在上一个例子中,我同时使用了ValidateModelState
和ExportModelState
,这是因为ValidateModelState
在ActionExecuting
上运行,所以它在进入方法体之前进行验证,如果绑定有一些验证错误,它将自动重定向。然后,我有另一个检查不能在数据注释中,因为它处理加载实体并查看它是否具有正确的要求(我知道这不是最好的例子,可以认为它是查看注册时提供的用户名是否可用,我知道远程数据注释,但不涵盖所有情况),然后我只根据外部情况使用自己的错误更新ModelState
除了绑定之外的其他因素。由于ExportModelState
在ActionExecuted
上运行,所以我对ModelState
的所有修改都在TempData
上持久化,所以我将在HttpGet
编辑操作中使用它们。
我知道所有这些都会让我们中的一些人感到困惑,对于如何在Controller/PRG端进行MVC,没有真正好的指示。我在写一篇博客文章以涵盖所有场景和解决方案时进行了认真思考。这只是其中的1%。
我希望至少我澄清了POST-GET工作流程的几个关键点。如果这让人困惑而没有帮助,请告诉我。抱歉发了这么长的邮件。
我还想注意的是,返回ActionResult的PRG与返回RedirectToRouteResult的有一个细微的差异。如果您在出现ValidationError后使用RedirectToRouteResult刷新页面(F5),则错误将不会持久存在,并且您将获得一个干净的视图,就像您第一次输入一样。使用ActionResult,您可以刷新并看到完全相同的页面,包括错误。这与ActionResult或RedirectToRouteResult返回类型无关,因为在一种情况下,您总是在POST时重定向,而在另一种情况中,您只在成功POST时重定向。PRG并不建议在不成功的POST上盲目重定向,但有些人更喜欢在每个帖子上进行重定向,这需要TempData传输。