Question

With this code I have error:

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();
}

Stack Trace:

 [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

If the model is not valid and you are unable to do execute some of your code in the

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

you need to return same model to the View()

return View(dev);

like u did with the get action,

otherwise the view cannot display because model is null.

when u do return View(dev); view will render fine, and if u did ModelState.AddModelError(/**/); the view will show validation errors