我遇到一个奇怪的问题….当我使用UpdateModel()或TryUpdateModel(),一切正常.当我尝试绑定自己(例如MyObject.FirstName = collection [“FirstName”])时,我得到一个“对象引用未设置为对象的实例”错误.
这有点难以解释,所以我将介绍代码：
[HandleError]
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create(FormCollection collection)
{
try
{
Model.Event evnt = new Redline.RedlineTimeAttack.Model.Event();
//When this is uncommented everything works fine.
//TryUpdateModel<Model.Event>(evnt);
//this will eventually lead to problems
evnt.Description = collection["Description"];
evnt.EndDate = enddate;
evnt.EventName = collection["EventName"];
evnt.IsActive = collection["IsActive"].Contains("true");
evnt.StartDate = startdate;
evnt.TrackId = trackId;
evnt.WebContent = collection["WebContent"];
if (!evnt.IsValid)
{
foreach (var error in evnt.GetRuleViolations())
{
ModelState.AddModelError(error.PropertyName,error.ErrorMessage);
}
}
//If there are no validation issues then no problem,redirecttoaction
//works properly
if (ModelState.IsValid)
{
model.Events.InsertOnSubmit(evnt);
model.SubmitChanges();
ViewData["ControlMode"] = "Edit";
return RedirectToAction("Edit");
}
else //returning to View so that user can correct issues causes a null reference error in the view (bombs at first Html.TextBox("ControlName"))
{
ViewData["Tracks"] = GetTracks();
return View("Create",evnt);
}
}
这是堆栈跟踪：
System.NullReferenceException was unhandled by user code Message="Object reference not set to an instance of an object." Source="System.Web.Mvc" StackTrace: at System.Web.Mvc.HtmlHelper.GetModelStateValue(String key,Type destinationType) at System.Web.Mvc.Html.InputExtensions.InputHelper(HtmlHelper htmlHelper,InputType inputType,String name,Object value,Boolean useViewData,Boolean isChecked,Boolean setId,Boolean isExplicitValue,IDictionary`2 htmlAttributes) at System.Web.Mvc.Html.InputExtensions.TextBox(HtmlHelper htmlHelper,String name) at ASP.views_event_create_aspx.__RenderContent2(HtmlTextWriter __w,Control parameterContainer) in d:\TFSProjects\Redline Time Attack\Main\Source\Redline.RedlineTimeAttack.Web\Views\Event\Create.aspx:line 18 at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer,ICollection children) at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) at System.Web.UI.Control.Render(HtmlTextWriter writer) at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer,ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer,ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) at ASP.views_shared_site_master.__Render__control1(HtmlTextWriter __w,Control parameterContainer) in d:\TFSProjects\Redline Time Attack\Main\Source\Redline.RedlineTimeAttack.Web\Views\Shared\Site.Master:line 29 at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer,ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer,ICollection children) at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) at System.Web.UI.Page.Render(HtmlTextWriter writer) at System.Web.Mvc.ViewPage.Render(HtmlTextWriter writer) at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer,ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint,Boolean includeStagesAfterAsyncPoint) InnerException:
解决方法
我在这里找到了一些洞察力：
http://forums.asp.net/p/1396019/3006051.aspx
If you don’t want to use Builtin Model
Binding,then to use Bultin Validation
(SanjaySutar want to use),for every
ModelError you add,you will need to
add a ModelValue:
ModelState.AddModelError(“Name”,“Bad
Name”);ModelState.SetModelValue(“Name”,
ValueProvider[“Name”]);
所以我更新了我的代码如下：
ModelState.SetModelValue("Description",new ValueProviderResult(ValueProvider["Description"].AttemptedValue,collection["Description"],System.Globalization.CultureInfo.CurrentCulture));
ModelState.SetModelValue("EventName",new ValueProviderResult(ValueProvider["EventName"].AttemptedValue,collection["EventName"],System.Globalization.CultureInfo.CurrentCulture));
ModelState.SetModelValue("EndDate",new ValueProviderResult(ValueProvider["EndDate"].AttemptedValue,collection["EndDate"],System.Globalization.CultureInfo.CurrentCulture));
ModelState.SetModelValue("StartDate",new ValueProviderResult(ValueProvider["StartDate"].AttemptedValue,collection["StartDate"],System.Globalization.CultureInfo.CurrentCulture));
ModelState.SetModelValue("TrackId",new ValueProviderResult(ValueProvider["TrackId"].AttemptedValue,collection["TrackId"],System.Globalization.CultureInfo.CurrentCulture));
ModelState.SetModelValue("WebContent",new ValueProviderResult(ValueProvider["WebContent"].AttemptedValue,collection["WebContent"],System.Globalization.CultureInfo.CurrentCulture));
我这样做的原因是因为我想要一个.在我的业务对象中完成所有(或尽可能多的)验证,包括必填字段和b.我在验证摘要中想要我自己的邮件(例如“FieldX是必填字段”,而不是“需要一个值”).如果有更好的方法,请参阅我的另一个问题：ASP.NET MVC – Custom validation message for value types
