C# 尝试循环时未将对象引用设置为对象的实例

请看这张图片：

我想在我的视图中循环浏览“TopTens”，我们可以看到其中有9个对象 “TopTens”，为什么会说：对象引用未设置为对象的实例

!！[在此处输入图像描述][1]

[NullReferenceException: Object reference not set to an instance of an object.]
   ASP._Page_Views_secure_CreatePageDetailss_cshtml.Execute() in c:\Users\xxx\xxx\xxxx\xxxxx\xxxxx\Views\Secure\CreatePageDetailss.cshtml:18
   System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +271
   System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +120
   System.Web.WebPages.StartPage.RunPage() +63
   System.Web.WebPages.StartPage.ExecutePageHierarchy() +100
   System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +131
   System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +695
   System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +382
   System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +431
   System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) +39
   System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) +116
   System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) +529
   System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult) +106
   System.Web.Mvc.Async.<>c__DisplayClass2b.<BeginInvokeAction>b__1c() +321
   System.Web.Mvc.Async.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult) +185
   System.Web.Mvc.Async.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult) +42
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +133
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +56
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +40
   System.Web.Mvc.Controller.<BeginExecuteCore>b__1d(IAsyncResult asyncResult, ExecuteCoreState innerState) +34
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +70
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +139
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +59
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40
   System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +44
   System.Web.Mvc.Controller.<BeginExecute>b__15(IAsyncResult asyncResult, Controller controller) +39
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +62
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +139
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +59
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40
   System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +39
   System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +39
   System.Web.Mvc.MvcHandler.<BeginProcessRequest>b__5(IAsyncResult asyncResult, ProcessRequestState innerState) +39
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +70
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +139
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +59
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40
   System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +40
   System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +38
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +9514928
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155

[NullReferenceException:对象引用未设置为对象的实例。]
ASP.\u Page\u Views\u secure\u CreatePageDetailss\u cshtml.Execute（）在c:\Users\xxx\xxx\xxxxx\xxxxx\Views\secure\CreatePageDetailss.cshtml:18中
System.Web.WebPages.WebPageBase.ExecutePageHierarchy（）+271
System.Web.Mvc.WebViewPage.ExecutePageHierarchy（）+120
System.Web.WebPages.StartPage.RunPage（）+63
System.Web.WebPages.StartPage.ExecutePageHierarchy（）+100
System.Web.WebPages.WebPageBase.ExecutePageHierarchy（WebPageContext pageContext、TextWriter writer、WebPageRenderingBase startPage）+131
System.Web.Mvc.RazorView.RenderView（ViewContext、TextWriter、Object实例）+695
System.Web.Mvc.BuildManagerCompiledView.Render（ViewContext，TextWriter）+382
System.Web.Mvc.ViewResultBase.ExecuteResult（ControllerContext上下文）+431
System.Web.Mvc.ControllerActionInvoker.InvokeActionResult（ControllerContext ControllerContext，ActionResult ActionResult）+39
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive（IList`1过滤器、Int32过滤器索引、ResultExecutingContext预文本、ControllerContext ControllerContext、ActionResult ActionResult）+116
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive（IList`1过滤器、Int32过滤器索引、ResultExecutingContext预文本、ControllerContext ControllerContext、ActionResult ActionResult）+529
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters（ControllerContext ControllerContext，IList`1过滤器，ActionResult ActionResult）+106
System.Web.Mvc.Async.c__显示类2B.b__1c（）+321
System.Web.Mvc.Async.c__显示类21.b__1e（IAsyncResult asyncResult）+185
System.Web.Mvc.Async.WrappedAsyncResult`1.CallEndDelegate（IAsyncResult asyncResult）+42
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End（）+133
System.Web.Mvc.Async.asyncResultRapper.End（IAsyncResult asyncResult，对象标记）+56
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction（IAsyncResult asyncResult）+40
System.Web.Mvc.Controller.b_u1d（IAsyncResult asyncResult，ExecuteCorerate innerState）+34
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate（IAsyncResult asyncResult）+70
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End（）+139
System.Web.Mvc.Async.asyncResultRapper.End（IAsyncResult asyncResult，对象标记）+59
System.Web.Mvc.Async.asyncResultRapper.End（IAsyncResult asyncResult，对象标记）+40
System.Web.Mvc.Controller.EndExecuteCore（IAsyncResult asyncResult）+44
System.Web.Mvc.Controller.b_uu15（IAsyncResult asyncResult，Controller-Controller）+39
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate（IAsyncResult asyncResult）+62
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End（）+139
System.Web.Mvc.Async.asyncResultRapper.End（IAsyncResult asyncResult，对象标记）+59
System.Web.Mvc.Async.asyncResultRapper.End（IAsyncResult asyncResult，对象标记）+40
System.Web.Mvc.Controller.EndExecute（IAsyncResult asyncResult）+39
System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute（IAsyncResult asyncResult）+39
System.Web.Mvc.MvcHandler.b_uu5（IAsyncResult asyncResult，ProcessRequestState innerState）+39
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate（IAsyncResult asyncResult）+70
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End（）+139
System.Web.Mvc.Async.asyncResultRapper.End（IAsyncResult asyncResult，对象标记）+59
System.Web.Mvc.Async.asyncResultRapper.End（IAsyncResult asyncResult，对象标记）+40
System.Web.Mvc.MvcHandler.EndProcessRequest（IAsyncResult asyncResult）+40
System.Web.Mvc.MvcHandler.System.Web.IHTTPassynchandler.EndProcessRequest（IAsyncResult结果）+38
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute（）+9514928
System.Web.HttpApplication.ExecuteStep（IExecutionStep步骤，布尔值&同步完成）+155

对于您给我们的代码，只有一种解释，即列表中有一项为

null

语句

@item.LongDesc

将抛出

NullReferenceException

如果允许

TopTens

中的一项为

null

，请添加null检查：

@if (@item != null)
{
  <p>@item.LongDesc</p>
}

@if（@item！=null）
{
@项目1.LongDesc

}

---

或者，如果

TopTens

是一个

列表

只需不添加更多的项目，那么就有了，这样就可以防止一个项目成为

null

对于您给我们的代码，只有一个解释，那就是列表中的一个项目是

null

语句

@item.LongDesc

将抛出

NullReferenceException

如果允许

TopTens

中的一项为

null

，请添加null检查：

@if (@item != null)
{
  <p>@item.LongDesc</p>
}

@if（@item！=null）
{
@项目1.LongDesc

}

---

或者，如果

TopTens

是一个

列表

，只需不添加更多的项目，就可以避免其中一个项目为

null

该集合中有9个项目，但您确定其中一个项目不是null吗？（我也会发布几行堆栈跟踪，带有行号，以发现此类“问题”）该集合中有9项的可能重复项，但您确定其中一项不是空的吗？（我会发布几行堆栈跟踪，以及行号，以发现此类“问题”）可能的重复谢谢！我尝试在foreach中添加if语句……但是断点显示，在抛出异常之前，代码甚至没有通过foreach的开头行。它甚至从未到达@item.LongDesc@user2915962