Knockout.js bind array of objects to repeated <select>'s - asp.net-mvc

Question

I've got this Knockout.js view model:
{
"LanguageFromTos":
[{
"LanguageFromToId":0,
"LanguageFromId":2,
"LanguageFrom":null,
"AllLanguagesFrom":[
{"Selected":false,"Text":"English","Value":"1"},
{"Selected":false,"Text":"French","Value":"2"},
{"Selected":false,"Text":"Spanish","Value":"3"}
],
"LanguageToId":1,
"LanguageTo":null,
"AllLanguagesTo":[
{"Selected":false,"Text":"English","Value":"1"},
{"Selected":false,"Text":"French","Value":"2"},
{"Selected":false,"Text":"Spanish","Value":"3"}
],
"Users":null
}]
}
And these html <select>s:
<div class="LanguageFromToRow">
<input type="hidden" name="languageFromTos.index" autocomplete="off" value="c50532b0-65d2-4a81-baeb-59b768fd120f" />
<label for="languageFromTos_c50532b0-65d2-4a81-baeb-59b768fd120f__LanguageFromId">From</label>:
<select data-bind="???" data-val="true" data-val-number="The field From must be a number." data-val-required="The From field is required." id="languageFromTos_c50532b0-65d2-4a81-baeb-59b768fd120f__LanguageFromId" name="languageFromTos[c50532b0-65d2-4a81-baeb-59b768fd120f].LanguageFromId">
<option value="1">English</option>
<option selected="selected" value="2">French</option>
<option value="3">Spanish</option>
</select>
<span class="field-validation-valid" data-valmsg-for="languageFromTos[c50532b0-65d2-4a81-baeb-59b768fd120f].LanguageFromId" data-valmsg-replace="true"></span>
<label for="languageFromTos_c50532b0-65d2-4a81-baeb-59b768fd120f__LanguageToId">To</label>:
<select data-bind="???" data-val="true" data-val-number="The field To must be a number." data-val-required="The To field is required." id="languageFromTos_c50532b0-65d2-4a81-baeb-59b768fd120f__LanguageToId" name="languageFromTos[c50532b0-65d2-4a81-baeb-59b768fd120f].LanguageToId">
<option selected="selected" value="1">English</option>
<option value="2">French</option>
<option value="3">Spanish</option>
</select>
<span class="field-validation-valid" data-valmsg-for="languageFromTos[c50532b0-65d2-4a81-baeb-59b768fd120f].LanguageToId" data-valmsg-replace="true"></span>
delete
</div>
Can anyone tell me what I need to add to the data-bind attributes of each select to tie them up to the Knockout.js view model? The value of the first select should be bound to LanguageFromId in the view model and the value of the second select should be bound to LanguageToId in the view model.
LanguageFromTos in the view model is an array, so all of what you see inside may be repeated (2 LanguageFromTos would result in the LanguageFromToRow div being repeated twice, for example). The number of repeats is set both server-side (data posted by the controller may have multiple LanguageFromTos) and client-side (an 'add' button that allows the user to add another div with its contained selects) in different cases, so I presume Knockout's templating is a no-go as MVC needs to loop through and render each row so that it can catch them all on a 'normal' post back.
Any help much appreciated!
Edit
Here's the MVC model for the page:
public class DirectorySearchModel
{
[Display(Name = "User name contains")]
public string UserName { get; set; }
[Display(Name = "First name contains")]
public string FirstName { get; set; }
[Display(Name = "Last name contains")]
public string LastName { get; set; }
[Display(Name = "Languages translated")]
public IEnumerable<LanguageFromTo> LanguageFromTos { get; set; }
}
Here's the LanguageFromTo object:
public class LanguageFromTo
{
[Key]
public virtual int LanguageFromToId { get; set; }
[Display(Name = "From")]
public virtual int LanguageFromId { get; set; }
[ForeignKey("LanguageFromId")]
public virtual Language LanguageFrom { get; set; }
public virtual IEnumerable<SelectListItem> AllLanguagesFrom { get; set; }
[Display(Name = "To")]
public virtual int LanguageToId { get; set; }
[ForeignKey("LanguageToId")]
public virtual Language LanguageTo { get; set; }
public virtual IEnumerable<SelectListItem> AllLanguagesTo { get; set; }
public virtual ICollection<User> Users { get; set; }
}
And here's the cshtml code for the MVC view. This code sits in a partial that's repeated depending on how many LanguageFromTos there are in DirectorySearchModel that's passed to the MVC view:
<div class="LanguageFromToRow">
#using(Html.BeginCollectionItem("languageFromTos")) {
#: #Html.LabelFor(m => m.LanguageFromId): #Html.DropDownListFor(m => m.LanguageFromId, Model.AllLanguagesFrom, new { data_bind = "value: getLanguageFromToById(0).LanguageFromId" }) #Html.ValidationMessageFor(m => m.LanguageFromId)
#: #Html.LabelFor(m => m.LanguageToId): #Html.DropDownListFor(m => m.LanguageToId, Model.AllLanguagesTo, new { data_bind = "value: getLanguageFromToById(0).LanguageToId" }) #Html.ValidationMessageFor(m => m.LanguageToId)
delete
}
</div>

Answer 1

Your design here has some poor choices. Knockout's Templating is the right choice for this, but it is going to require you to start thinking in a different sort of pattern. You do not need to use partials to accomplish the repetition you are after.
Here is a fiddle demonstrating a templating solution. http://jsfiddle.net/tyrsius/XgwLD/3/
Some notes: to populate incomingData, an easy method will be to use #Html.Raw(Json.Encode(Model.DirectorySearchModel ));. This will turn your model into a JSON object, which the viewModel's constructor can easily use.
Now, I didn't use any MVC code in the fiddle because I can't, but you've obviously already found how you can put data-bind in the MVC helpers. This isn't always a bad idea, but for things like selects and DIVs that you want to use as templates, it will probably just makes things harder to read.