对象引用未设置到对象

Question

有了这个代码的实例，我有错误：

Object reference not set to an instance of an object

<% using (Html.BeginForm("XMLDevicesAddFirmware","ImportXML",FormMethod.Post)) {%> 

<table class="data-table"> 
    <tr> 
     <th>Article Number</th> 
     <th>Firmware</th> 
     <th>Name</th> 
     <th>Order Id</th> 
     <th>Software Version</th> 
    </tr> 

<% int rb = 1;%> 

<% foreach (var item in Model) { %> 
    <tr> 
     <td><%= Html.Encode(item.ArticleNumber) %></td> 
     <td><input id="Firmware" name="<%= Html.Encode(rb)%>" type="text" /></td> 
     <td><%= Html.Encode(item.Name) %></td> 
     <td><%= Html.Encode(item.OrderId) %></td> 
     <td><input id="SoftwareVersion" name="<%= Html.Encode(rb)%>" type="text" /></td> 
    </tr> 
    <% rb = rb + 1;%> 
    <% } %> 

</table> 
<p> 
    <input type="submit" value="Finish" /> 
</p> 
<% } %> 


public ActionResult XMLDevicesAddFirmware() 
{ 
    var dev = from i in XMLEntities.unassigneditems 
       where i.DevOrAcc == true 
       select i; 
    return View(dev); 
} 



[AcceptVerbs(HttpVerbs.Post)] 
public ActionResult XMLDevicesAddFirmware(FormCollection col) 
{ 
    //.... 
    return View(); 
} 

堆栈跟踪：

[NullReferenceException: Object reference not set to an instance of an object.] 
ASP.views_importxml_xmldevicesaddfirmware_aspx.__RenderContent2(HtmlTextWriter __w,  Control parameterContainer) in c:\Documents and Settings\Ognjen\My Documents\Visual Studio 2008\Projects\MvcKVteam - radna verzija_18_07\MvcKVteam - radna verzija\MvcKVteam\Views\ImportXML\XMLDevicesAddFirmware.aspx:36 
System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +256 
System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19 
System.Web.UI.Control.Render(HtmlTextWriter writer) +10 
System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27 
System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99 
System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25 
ASP.views_shared_site_master.__Render__control1(HtmlTextWriter __w, Control parameterContainer) in c:\Documents and Settings\Ognjen\My Documents\Visual Studio 2008\Projects\MvcKVteam - radna verzija_18_07\MvcKVteam - radna verzija\MvcKVteam\Views\Shared\Site.Master:104 
System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +256 
System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19 
System.Web.UI.Control.Render(HtmlTextWriter writer) +10 
System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27 
System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99 
System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25 
System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +134 
System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19 
System.Web.UI.Page.Render(HtmlTextWriter writer) +29 
System.Web.Mvc.ViewPage.Render(HtmlTextWriter writer) +59 
System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27 
System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99 
System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25 
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1266 

Answer 1

如果模型是无效的，你不能这样做在

执行一些代码的

[AcceptVerbs(HttpVerbs.Post)] 
public ActionResult XMLDevicesAddFirmware(FormCollection col) 
{ 
    //.... 
    return View(); 
} 

需要同型号返回查看（）

return View(dev); 

像你那样与取得动作，

否则视图无法显示，因为模型为空。

当u做return View(dev);视图将呈现精细，如果ü没有ModelState.AddModelError(/**/);视图将显示在结合或回传

Answer 2

是方法公众的ActionResult XMLDevicesAddFirmware（串固件，字符串SoftwareVersion）被击中。我看不到你的表单发回这个方法，我的意思是，路由中没有字符串Firmware，字符串SoftwareVersion。

试试这个

[AcceptVerbs(HttpVerbs.Post)] 
    public ActionResult XMLDevicesAddFirmware(FormCollection coll) 
    { 
     //.... 
     return View(); 
    } 

编辑：或在Html.BeginForm添加新{固件= Model.Firmware，SoftwareVersion = Model.SoftwareVersion}

Answer 3

不要忘了模型传递到观点：

[AcceptVerbs(HttpVerbs.Post)] 
public ActionResult XMLDevicesAddFirmware(string Firmware, string SoftwareVersion) 
{ 
    var model = new SomeModel(); 
    return View(model); 
}