drop down menu - How to post the selected value of a selectlist to the controller using a view model? -

this question has been asked in various forms none of answers seem fit situation. trying retrieve selected value of dropdown list in controller.

here code:

viewmodel.cs

public class viewmodel {   public viewmodel() {}   public viewmodel(contact contact, ienumerable<state> states)     {       this.contact = contact;       this.states = new selectlist(states, "id", "name", contact.stateid);     }   public contact contact {get;set;}   public selectlist states {get;set;} } 

controller.cs

[httppost] public actionresult edit(viewmodel viewmodel) {   _contactservice.updatecontact(viewmodel.contact);   return redirecttoaction("item", new {id = viewmodel.contact.id}); } 

view.cshtml

<button type="submit" onclick="javascript:document.update.submit()"><span>update</span></button>//aesthic usage.  @{using (html.beginform("edit", "controller", formmethod.post, new { name = "update" }))   {    @html.hiddenfor(m => m.contact.id)    @html.labelfor(m => m.contact.name, "name:")    @html.textboxfor(m => m.contact.name)     <label for="state">state:</label>    @html.dropdownlist("state", model.states) } } 

everything works expected except no values dropdownlist passed in posted viewmodel controller. edit page , fields load correctly. dropdowns bind correctly , have selected values displayed properly. however, when post "contact" object passed controller. "states" selectlist object null.

i tried mapping "stateid" property in viewmodel contstructor did not work either. doing wrong?

thanks.

i hate answering own questions based on multiple issues had coupled myriad of answers available thought summarize findings.

first off filip, answer did not fix problem led me in right direction. +1

if creating form viewing , editing requires drop down list, here suggestions , gotchas. start list of parameters needed fit needs.

1. strongly typed views in view preferable. minimize magic strings.
2. view models should contain little logic , extraneous elements possible. there job should facilitate collection of data objects.
3. the drop down list should display selected value.
4. the selected value should map view model on form submit.

this may sound obvious , obtainable list new mvc, not. revise code above comments. here did.

viewmodel.cs

public class viewmodel {   public viewmodel() {}   public viewmodel(contact contact, ilist<state> states)   { //no need pass in selectlist or ienumerable, service or repository spits out     this.contact = contact;     this.states = states;   }   public contact contact {get;set;}   public ilist<state> states {get;set;} } 

controller.cs //nothing different above

public actionresult edit(int id) {   var contact = _contactservice.getcontactbyid(id);   var states = _stateservice.getallstates();   return view(new viewmodel(contact, states)); }  public actionresult edit(viewmodel viewmodel) {   _contactservice.updatecontact(viewmodel.contact);   return redirecttoaction("edit", new {id = viewmodel.contact.id }); } 

view//thanks goes artirto @ post

@{using (html.beginform("edit", "controller", formmethod.post))  {   @html.hiddenfor(m => m.contact.id)   @html.dropdownlistfor(m => m.contact.stateid, new selectlist(model.states, "id", "name", @model.contact.stateid)) <input type="submit" value="save" /> } }