How can I get this ASP NET MVC SelectList to work

Question

I create a selectList in my controller  to display in the view   I m trying to create it on the fly  sorta thing    like this     myViewData PageOptionsDropDown       new SelectList new      10    15    25    50    100    1000     15      It compiles  but the output is bad      lt select id  PageOptionsDropDown  name  PageOptionsDropDown  gt       lt option gt 10 lt  option gt       lt option gt 15 lt  option gt       lt option gt 25 lt  option gt       lt option gt 50 lt  option gt       lt option gt 100 lt  option gt       lt option gt 1000 lt  option gt   lt  select gt    Notice how no item is selected   How can I fix this

User · Answer

I use an extension method   usage  var departmentItems   departments ToSelectList d   gt  d Code                                                     -     d Description                                                 d   gt  d Id ToString                                                     -      var functionItems   customerFunctions ToSelectList f   gt  f Description                                                      f   gt  f Id ToString                                                          -       with  public static class MCVExtentions       public static List lt SelectListItem gt  ToSelectList lt T gt           this IEnumerable lt T gt  enumerable           Func lt T  string gt  text           Func lt T  string gt  value           string defaultOption                var items   enumerable Select f   gt  new SelectListItem                                                                                   Text   text f                                             Value   value f                                           ToList            items Insert 0  new SelectListItem                                                 Text   defaultOption                           Value    -1                                   return items

User · Answer

It seems if you have a strongly typed view you need to change the ID of the dropdown so that it is NOT the name of a property on the inherrited class  You then need to put some logic in your edit  POST  method to pull off the selected value from the FORMCollection and put it on to your instance before committing your changes   This is certainly a little strange  but i tried it and it works   So if you class has a field called CountryId say  and you re displaying a list of country names  make the dropdown have an id of CountryName rather than CountryId  then in the post  you can do something with Collection  CountryName

User · Answer

If you want to pass some random text to your DropDownList  for example --Select-- you can easy do this using this code    Html DropDownListFor x   gt  x CategoryId  new SelectList Model Categories   Id    Name     --Select--   new    class    form-control

User · Answer

If you have a collection in your model and your View is strongly type  some variation of this will work    Html DropDownListFor x   gt  x RegionID       new SelectList Model Regions  RegionID    RegionName   Model RegionID     -or-   Html DropDownList  RegionID        new SelectList Model Regions   RegionID    RegionName   Model RegionID

User · Answer

I do it like this   List lt SelectListItem gt  list   new List lt SelectListItem gt   new SelectListItem  Selected   true  Text    Select   Value    0    new SelectListItem  Selected   true  Text    1   Value    1    new SelectListItem  Selected   true  Text    2   Value    2      return list ToArray      The ToArray   takes care of the problems

User · Answer

If that s literally all you want to do then just declaring the array as string fixes the selected item problem   myViewData PageOptionsDropDown       new SelectList new string     10    15    25    50    100    1000     15

User · Answer

Simple   string   someName   new string     10    15    25    50    100    1000    myViewData PageOptionsDropDown   new SelectList someName   15

User · Answer

A possible explanation is that the selectlist value that you are binding to is not a string   So in that example  is the parameter  PageOptionsDropDown  a string in your model  Because if it isn t then the selected value in the list wouldn t be shown

User · Answer

It may be the case that you have some ambiguity in your ViewData   Take a look Here

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This is an option   myViewData PageOptionsDropDown   new       new SelectListItem   Text    10   Value    10      new SelectListItem   Text    15   Value    15   Selected   true    new SelectListItem   Text    25   Value    25      new SelectListItem   Text    50   Value    50      new SelectListItem   Text    100   Value    100      new SelectListItem   Text    1000   Value    1000

User · Answer

I had the exact same problem  The solution is simple  Just change the  name  parameter passed to the DropDownList helper to something that does not match any of the properties existing in your ViewModel   read more here  http   www dotnetguy co uk post 2009 06 25 net-mvc-selectlists-selected-value-does-not-get-set-in-the-view  I quote the Dan Watson      In MVC if the view is strongly typed the selectlist   s selected option will be overridden and the selected option property set on the constructor will never reach the view and the first option in the dropdown will be selected instead  why is still a bit of a mystery      cheers

User · Answer

Building off Thomas Stock s answer  I created these overloaded ToSelectList methods   using System  using System Collections Generic  using System Linq  using System Web Mvc   public static partial class Helpers       public static IEnumerable lt SelectListItem gt  ToSelectList lt T gt  this IEnumerable lt T gt  enumerable  Func lt T  object gt  value  bool selectAll   false                return enumerable ToSelectList value  value  selectAll              public static IEnumerable lt SelectListItem gt  ToSelectList lt T gt  this IEnumerable lt T gt  enumerable  Func lt T  object gt  value  object selectedValue                return enumerable ToSelectList value  value  new List lt object gt      selectedValue                public static IEnumerable lt SelectListItem gt  ToSelectList lt T gt  this IEnumerable lt T gt  enumerable  Func lt T  object gt  value  IEnumerable lt object gt  selectedValues                return enumerable ToSelectList value  value  selectedValues              public static IEnumerable lt SelectListItem gt  ToSelectList lt T gt  this IEnumerable lt T gt  enumerable  Func lt T  object gt  value  Func lt T  object gt  text  bool selectAll   false                foreach  var f in enumerable Where x   gt  x    null                         yield return new SelectListItem                                 Value   value f  ToString                    Text   text f  ToString                    Selected   selectAll                                     public static IEnumerable lt SelectListItem gt  ToSelectList lt T gt  this IEnumerable lt T gt  enumerable  Func lt T  object gt  value  Func lt T  object gt  text  object selectedValue                return enumerable ToSelectList value  text  new List lt object gt      selectedValue                public static IEnumerable lt SelectListItem gt  ToSelectList lt T gt  this IEnumerable lt T gt  enumerable  Func lt T  object gt  value  Func lt T  object gt  text  IEnumerable lt object gt  selectedValues                var sel   selectedValues    null               selectedValues Where x   gt  x    null  ToList   ConvertAll lt string gt  x   gt  x ToString                  new List lt string gt              foreach  var f in enumerable Where x   gt  x    null                         yield return new SelectListItem                                 Value   value f  ToString                    Text   text f  ToString                    Selected   sel Contains value f  ToString                                       In your controller  you might do the following   var pageOptions   new      10    15    25    50    100    1000     ViewBag PageOptions   pageOptions ToSelectList o   gt  o   15    selectedValue       And finally in your View  put    Html DropDownList  PageOptionsDropDown   ViewBag PageOptions as IEnumerable lt SelectListItem gt     Select one      It will result in the desired output--of course  you can leave out the   Select one   optionLabel above if you don t want the first empty item    lt select id  PageOptionsDropDown  name  PageOptionsDropDown  gt   lt option value    gt  Select one  lt  option gt   lt option value  10  gt 10 lt  option gt   lt option selected  selected  value  15  gt 15 lt  option gt   lt option value  25  gt 25 lt  option gt   lt option value  50  gt 50 lt  option gt   lt option value  100  gt 100 lt  option gt   lt option value  1000  gt 1000 lt  option gt   lt  select gt    Update  A revised code listing can be found here with XML comments

User · Answer

If you look in the source code for MVC 2 at the Html DropDownList extension method  it never checks the SelectList class SelectedValue property  It will only ever try to match against your Model   All the above are all variations on a theme  ie how do you send a bunch of data to the view to for a drop-down list  amp  they re all as good as each other  more-or-less     The problem is in the view  Either create your own DropDownList extension method that does respect the selectvalue you set  or iterate though by hand  Which ever works best for you

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MonthRepository monthRepository   new MonthRepository    IQueryable lt MonthEntity gt  entities   monthRepository GetAllMonth    List lt MonthEntity gt  monthEntities   new List lt MonthEntity gt      foreach var r in entities        monthEntities Add r      ViewData  Month     new SelectList monthEntities   MonthID    Month    Mars

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I can t remember how mvc 1 was setup  but it seems that it wanted the select list named the same as the field it belonged too     What I found  as someone kind of said above  is that my select lists weren t working in mvc2 when the ViewData they were sent as was named the same as the field   For example    lt    Html DropDownListFor  model   gt  model ForID    SelectList ViewData  ForName      gt   works when   lt    Html DropDownListFor  model   gt  model ForID    SelectList ViewData  ForID      gt   does not work as the ViewData name  ForID  is named the same as the field it is working for

User · Answer

This is how I do it  IList lt Customer gt  customers   repository GetAll lt Customer gt     IEnumerable lt SelectListItem gt  selectList        from c in customers     select new SelectListItem               Selected    c CustomerID    invoice CustomerID           Text   c Name          Value   c CustomerID ToString            At second glance I m not sure I know what you are after

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Using the constructor that accepts items  dataValueField  dataTextField  selectedValue as parameters    ViewData  myList                      new SelectList new      10    15    25    50    100    1000                     Select x    new  value   x  text   x                      value    text    15      Then in your view     lt   Html DropDownList  myList     gt

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It s very simple to get SelectList and SelectedValue working together  even if your property isn t a simple object like a Int  String or a Double value   Example   Assuming our Region object is something like this   public class Region        public Guid ID   get  set         public Guid Name   get  set        And your view model is something like   public class ContactViewModel        public DateTime Date   get  set         public Region Region   get  set         public List lt Region gt  Regions   get  set        You can have the code below    Html DropDownListFor x   gt  x Region  new SelectList Model Regions   ID    Name       Only if you override the ToString method of Region object to something like   public class Region        public Guid ID   get  set         public Guid Name   get  set          public override string ToString                   return ID ToString               This have 100  garantee to work   But I really believe the best way to get SelectList 100  working in all circustances is by using the Equals method to test DropDownList or ListBox property value against each item on items collection

User · Answer

All these answers look great  but seems to be that the controller is preparing data for a View in a well-known structured format vs  letting the view simply iterate an IEnumerable lt   delivered via the model and build a standard select list then let DefaultModelBinder deliver the selected item back to you via an action parameter   Yes  no  why not   Separation of concerns  yes   Seems odd to have the controller to build something so UI and View specific

User · Answer

Using your example this worked for me   controller   ViewData  PageOptionsDropDown     new SelectList new      10    15    25    50    100    1000      15      view    lt    Html DropDownList  PageOptionsDropDown    gt

User · Answer

The problem is  SelectList works as designed  The bug is in the design  You may set the Selected Property in SelectedItem  but this will completely be ignored   if you traverse the list with the GetEnumerator    or if Mvc does that for you   Mvc will create new SelectListItems instead   You have to use the SelectList ctor with the SelectListItem    the Text-Name  the Value-Name and the SelectedValue  Be aware to pass as SelectedValue the VALUE of SelectListItem  which you want to be selected  not the SelectListItem itself  Example   SelectList sl   new SelectList  new      new SelectListItem  Text  one   Value  1      new SelectListItem  Text  two   Value  2      new SelectListItem  Text  three   Value  3       Text    Value    2        not tested this  but I had the same problem   then the 2nd option will get the selected  selected  attribute  That looks like good old DataSets  -

User · Answer

the value selected in the model takes advantage instead of the default item   I agree I didn t read all posts

User · Answer

I just ran it like this and had no problems   public class myViewDataObj               public SelectList PageOptionsDropDown   get  set           public ActionResult About                         myViewDataObj myViewData   new myViewDataObj                myViewData PageOptionsDropDown                     new SelectList new      10    15    25    50    100    1000      15                 ViewData  myList     myViewData PageOptionsDropDown              return View                and   lt   Html DropDownList  myList     gt    it also worked if you do this   public ActionResult About                         myViewDataObj myViewData   new myViewDataObj                myViewData PageOptionsDropDown                     new SelectList new      10    15    25    50    100    1000                   ViewData  myListValues     myViewData PageOptionsDropDown              ViewData  myList      15               return View                and   lt   Html DropDownList  myList   IEnumerable lt SelectListItem gt  ViewData  myListValues      gt

[c#] How can I get this ASP.NET MVC SelectList to work?

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