binding asp.net mvc form element to complex object for posting to controller

Question

I am trying to refactor to avoid parsing the FormCollection from the view so i changed this to pass in an strongly typed object. My form elements are the same names as the properties on the LinkUpdater Object. But when i put a breakpoint on the first link in the controller all of the properties are null.

any ideas or suggestions?

View:

 <%using (Ajax.BeginForm("AddNewLink", "Links", new AjaxOptions { UpdateTargetId = "LinkList", LoadingElementId = "updating", OnSuccess = "done" }))
  { %>

 <fieldset style="text-align:left">
 <table>
 <tr><td>Url:</td><td> <input style="width:500px" type="text" name="URL" /></td></tr>
 <tr><td>Description: </td><td><input style="width:400px" type="text" name="Description" /></td></tr>
 <tr><td>Tags: </td><td><input style="width:400px" id="Tags" name="tags" type="text" /></td></tr>
 <tr><td><input type="submit" value="Add Link" name="submit" /></td></tr>
 </table>
 </fieldset>
  <% } %>

Controller Post:

    [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult AddNewLink(LinkUpdater linkUpdater_)
    {
        string[] tags = linkUpdater_.Tags.Replace(" ", "").Split(',');
        linkRepository.AddLink(linkUpdater_.URL, linkUpdater_.Description, tags);
        .....
    }

LinkUpdater class:

public class LinkUpdater
{
    public string URL;
    public string Description;
    public string Tags;
}

Answer 1

Is there any particular reason your are not using the strongly-typed HTMLHelpers to render your input fields?

<%using (Ajax.BeginForm("AddNewLink", "Links", new AjaxOptions { UpdateTargetId = "LinkList", LoadingElementId = "updating", OnSuccess = "done" }))
  { %>
<fieldset style="text-align: left">
 <table>
  <tr>
   <td>
    Url:
   </td>
   <td>
    <%=Html.TextBox("URL", Model.URL, new { style = "width:500px;" }) %>
   </td>
  </tr>
  <tr>
   <td>
    Description:
   </td>
   <td>
    <%=Html.TextBox("Description", Model.Description, new { style = "width:400px;" }) %>
   </td>
  </tr>
  <tr>
   <td>
    Tags:
   </td>
   <td>
    <%=Html.TextBox("Tags", Model.Tags, new { style = "width:400px;" }) %>
   </td>
  </tr>
  <tr>
   <td>
    <input type="submit" value="Add Link" name="submit" />
   </td>
  </tr>
 </table>
</fieldset>
<% } %>

I'm not sure it will fix your problem, but it's a step in the right direction at least.

Answer 2

Model binder in MVC binds to properties, while you use fields. Change to

public string URL { get; set; }

And by the way, there're other drawbacks, like if you use private set, it will silently skip binding, too.