Question

I have a view model property to hold a list of dropdown selection values like:

  private ListDictionary _claimDropdownValueCollection = new ListDictionary();
  public ListDictionary ClaimDropdownValueCollection { get { return _claimDropdownValueCollection; } set { _claimDropdownValueCollection = value; } }

On doing the GET, I am looping over a different ListDictionary also in my view model which contains “dropdown type” names:

@foreach (System.Collections.DictionaryEntry de in Model.CCSetting_ClaimDropdownTypeCollection) {
                        <div class="formRow">
                            <label>@EverythingToDoWith_CCSetting_ClaimDropdownTypes.getDropdownTypeName(Model.ccClaim.clientID, Convert.ToInt32(de.Key))</label>
                            <div class="formRight searchDrop">
                                @Html.DropDownListFor(m => m.ClaimDropdownValueCollection[@de.Key], (IEnumerable<SelectListItem>) @de.Value, new { @class = "chzn-select", @data_placeholder="Choose an option...", @style="width: 350px;" })
                            </div>
                            <div class="clear"></div>
                        </div>
                    }

So basically, this loads a bunch of dropdowns, their ‘label’ is printed as per the key in the dictionary. The ‘values’ for EACH dropdown are obtained from the VALUE of each dictionary, which contains an IENUMERABLE each.

All good so far. Now the user makes his selection on each dropdown and I do an HTTP POST. In the browser developer tools, I see the following data being posted back:

ClaimDropdownValueCollection[1]:2
ClaimDropdownValueCollection[2]:5
ClaimDropdownValueCollection[3]:
ClaimDropdownValueCollection[4]:11

So that is 4 dropdowns with keys 1,2,3,4 (my keys will be more complicated, simple keys here for my example’s sake) and three of the four have selections so I pass back the selected ID’s 2, 5 and 11.

But the problem is, I am unable to see this data as part of the view model listdictionary object when I debug inside the [HttpPost] controller method that receives the posted data. That is showing the “ClaimDropdownValueCollection” property to be empty.

I am expecting to be able to say something like:

foreach (DictionaryEntry de in vm.ClaimDropdownValueCollection) {
//do something here with de.Key and de.Value                        
                    }

So what am I doing wrong in the RAZOR code?… Help!

Answer 1

The issue was with the HTML helpers and how I was posting back. Here’s how I resolved it (thanks to my CTO at work!):

Created my view model property that will serve as the resource to populate from as:

Dictionary<int, List<SelectListItem>> CCSetting_ClaimDropdownTypeCollection

Created another dictionary with the SAME KEYS, whose VALUE will be the users selection:

Dictionary<int, int> ClaimDropdownValueCollection

Now on the RAZOR side, I am doing something like this (note the use of HTML.Hidden, and HTML.Dropdown instead of HTML.DropdownFor):

@foreach (var de in Model.CCSetting_ClaimDropdownTypeCollection) {
                        <div class="formRow">
                                                            <div class="formRight searchDrop">
@Html.Hidden("ClaimDropdownValueCollection[" + @de.Key + "]", @de.Key)
                                @Html.DropDownList("ClaimDropdownValueCollection[" +  @de.Value + "]", @de.Value, new { @class = "chzn-select", @data_placeholder="Choose an option...", @style="width: 350px;" })
                            </div>
                            <div class="clear"></div>
                        </div>
                    }

Sorry about not wording my question in a better way perhaps, I perhaps posted after hours of frustration and ended up doing a bad job at phrasing it. Getting the ‘Tumbleweed’ badge for this question motivated me to come back and post the solution. OK to close, hope someone someday runs into this!