MVC - Set selected value of SelectList

Question

How can I set the selectedvalue property of a SelectList after it was instantiated without a selectedvalue   SelectList selectList   new SelectList items   ID    Name      I need to set the selected value after this stage

User · Answer

The below code solves two problems  1  dynamically set the selected value of the dropdownlist and 2  more importantly to create a dropdownlistfor for an indexed array in the model  the problem here is that everyone uses one instance of the selectlist which is the ViewBoag List  while the array needs one Selectlist instance for each dropdownlistfor to be able to set the selected value    create the ViewBag variable as List  not SelectList  int he controller    controller code ViewBag Role   db LUT Role ToList       in the view  Html DropDownListFor m    m Contacts i  Role  new SelectList ViewBag Role  ID   Role  Model Contacts i  Role

User · Answer

Use LINQ and add the condition on the  quot selected quot  as a question mark condition      var listSiteId    from site in db GetSiteId   ToList                                         select new SelectListItem                                                                                   Value   site SITEID                                            Text   site NAME                                            Selected    dimension DISPLAYVALUE    site SITEID    true   false                                           ToList                        ViewBag SiteId   listSiteId

User · Answer

Simply use the third parameter for selected value in mvc4   Html DropDownList  CountryList   new SelectList ViewBag Countries   Value    Text   974      Here  974  is selected Value Specified  In my result selected country is now qatar in C  as below         foreach  CountryModel item in CountryModel GetCountryList                          if  item CountryPhoneCode Trim       974                                 countries Add new SelectListItem   Text   item CountryName           item CountryPhoneCode        Value   item CountryPhoneCode                                else                     countries Add new SelectListItem   Text   item CountryName           item CountryPhoneCode        Value   item CountryPhoneCode Selected true

User · Answer

Why are you trying to set the value after you create the list   My guess is you are creating the list in your model instead of in your view   I recommend creating the underlying enumerable in your model and then using this to build the actual SelectList    lt    Html DropDownListFor m   gt  m SomeValue  new SelectList Model ListOfValues   Value    Text   Model SomeValue     gt    That way your selected value is always set just as the view is rendered and not before   Also  you don t have to put any unnecessary UI classes  i e  SelectList  in your model and it can remain unaware of the UI

User · Answer

A bit late to the party here but here s how simple this is   ViewBag Countries   new SelectList countries GetCountries     id    countryName    82      this uses my method getcountries to populate a model called countries  obviousley you would replace this with whatever your datasource is  a model etc  then  sets the id as the value in the selectlist  then just add the last param  in this case  82  to select the default selected item    edit  Here s how to use this in Razor    Html DropDownListFor model   gt  model CountryId   IEnumerable lt SelectListItem gt  ViewBag Countries  new    class    form-control       Important  Also  1 other thing to watch out for  Make sure the model field that you use to store the selected Id  in this case model CountryId  from the dropdown list is nullable and is set to null on the first page load  This one gets me every time   Hope this saves someone some time

User · Answer

I ended up here because SelectListItem is no longer picking the selected value correctly  To fix it  I changed the usage of EditorFor for a  manual  approach            lt select id  Role  class  form-control  gt               foreach  var role in ViewBag Roles                                if  Model Roles First   RoleId    role Value                                         lt option value   role Value  selected gt  role Text lt  option gt                                    else                                        lt option value   role Value  gt  role Text lt  option gt                                           lt  select gt    Hope it helps someone

User · Answer

In case someone is looking I reposted my answer from  SelectListItem selected   true not working in view  After searching myself for answer to this problem - I had some hints along the way but this is the resulting solution for me  It is an extension Method  I am using MVC 5 C  4 52 is the target  The code below sets the Selection to the First Item in the List because that is what I needed  you might desire simply to pass a string and skip enumerating - but I also wanted to make sure I had something returned to my SelectList from the DB   Extension Method    public static class SelectListextensions    public static System Web Mvc SelectList SetSelectedValue    this System Web Mvc SelectList list  string value                if  value    null                        var selected   list Where x    x Text    value  FirstOrDefault                selected Selected   true                    return list           And for those who like the complete low down  like me  here is the usage  The object Category has a field defined as Name - this is the field that will show up as Text in the drop down  You can see that test for the Text property in the code above   Example Code    SelectList categorylist   new SelectList dbContext Categories   Id    Name     SetSelectedItemValue categorylist    select list function    private SelectList SetSelectedItemValue SelectList source       Category category   new Category     SelectListItem firstItem   new SelectListItem     int selectListCount   -1   if  source    null  amp  amp  source Items    null        System Collections IEnumerator cenum   source Items GetEnumerator         while  cenum MoveNext                  if  selectListCount    -1                        selectListCount   0                     selectListCount    1           category    Category cenum Current           source SetSelectedValue category Name            break            if  selectListCount  gt  0                foreach  SelectListItem item in source Items                        if  item Value    cenum Current ToString                                  item Selected   true                   break                                  return source       You can make this a Generic All Inclusive function   Extension - but it is working as is for me

User · Answer

Doug answered my question    But I ll explain what my problem was exactly  and how Doug helped me solve my problem which you could be encountering   I call jquery   post and am replacing my div with my partial view  like so   function AddNewAddress  paramvalue          post url    param  paramvalue   function d                myDiv   replaceWith d               When doing so  for some reason when stepping into my model my selected value affiliated property was never set  only until I stepped into the view it came into scope   So  What I had before   Html DropDownListUnobtrusiveFor model   gt  model CustomerAddresses i  YearsAtAddress  Model CustomerAddresses i  YearsAtAddressSelectList  new  onchange    return Address AddNewAddress this       Url Action  AddNewAddress    Address            i           however even though Model CustomerAddresses i  YearsAtAddressSelectList  was set    it didn t set the selected value   So after        Html DropDownListUnobtrusiveFor model   gt  model CustomerAddresses i  YearsAtAddress  new SelectList Model CustomerAddresses i  YearsAtAddressSelectList   Value    Text   Model CustomerAddresses i  YearsAtAddress   new   onchange    return Address AddNewAddress this       Url Action  AddNewAddress    Address            i            and it worked   I decided not to use DropDownListFor as it has problem when using unobtrusive validation  which is why i reference the following if your curious in a class classed   HtmlExtensions cs      SuppressMessage  Microsoft Design    CA1006 DoNotNestGenericTypesInMemberSignatures   Justification    This is an appropriate nesting of generic types     public static MvcHtmlString DropDownListUnobtrusiveFor lt TModel  TProperty gt  this HtmlHelper lt TModel gt  htmlHelper  Expression lt Func lt TModel  TProperty gt  gt  expression  IEnumerable lt SelectListItem gt  selectList        return DropDownListUnobtrusiveFor htmlHelper  expression  selectList  null    optionLabel     null    htmlAttributes            SuppressMessage  Microsoft Design    CA1006 DoNotNestGenericTypesInMemberSignatures   Justification    This is an appropriate nesting of generic types     public static MvcHtmlString DropDownListUnobtrusiveFor lt TModel  TProperty gt  this HtmlHelper lt TModel gt  htmlHelper  Expression lt Func lt TModel  TProperty gt  gt  expression  IEnumerable lt SelectListItem gt  selectList  object htmlAttributes        return DropDownListUnobtrusiveFor htmlHelper  expression  selectList  null    optionLabel     new RouteValueDictionary htmlAttributes          SuppressMessage  Microsoft Design    CA1006 DoNotNestGenericTypesInMemberSignatures   Justification    This is an appropriate nesting of generic types     public static MvcHtmlString DropDownListUnobtrusiveFor lt TModel  TProperty gt  this HtmlHelper lt TModel gt  htmlHelper  Expression lt Func lt TModel  TProperty gt  gt  expression  IEnumerable lt SelectListItem gt  selectList  IDictionary lt string  object gt  htmlAttributes        return DropDownListUnobtrusiveFor htmlHelper  expression  selectList  null    optionLabel     htmlAttributes         SuppressMessage  Microsoft Design    CA1006 DoNotNestGenericTypesInMemberSignatures   Justification    This is an appropriate nesting of generic types     public static MvcHtmlString DropDownListUnobtrusiveFor lt TModel  TProperty gt  this HtmlHelper lt TModel gt  htmlHelper  Expression lt Func lt TModel  TProperty gt  gt  expression  IEnumerable lt SelectListItem gt  selectList  string optionLabel        return DropDownListUnobtrusiveFor htmlHelper  expression  selectList  optionLabel  null    htmlAttributes            SuppressMessage  Microsoft Design    CA1006 DoNotNestGenericTypesInMemberSignatures   Justification    This is an appropriate nesting of generic types     public static MvcHtmlString DropDownListUnobtrusiveFor lt TModel  TProperty gt  this HtmlHelper lt TModel gt  htmlHelper  Expression lt Func lt TModel  TProperty gt  gt  expression  IEnumerable lt SelectListItem gt  selectList  string optionLabel  object htmlAttributes        return DropDownListUnobtrusiveFor htmlHelper  expression  selectList  optionLabel  new RouteValueDictionary htmlAttributes          SuppressMessage  Microsoft Design    CA1011 ConsiderPassingBaseTypesAsParameters   Justification    Users cannot use anonymous methods with the LambdaExpression type      SuppressMessage  Microsoft Design    CA1006 DoNotNestGenericTypesInMemberSignatures   Justification    This is an appropriate nesting of generic types     public static MvcHtmlString DropDownListUnobtrusiveFor lt TModel  TProperty gt  this HtmlHelper lt TModel gt  htmlHelper  Expression lt Func lt TModel  TProperty gt  gt  expression  IEnumerable lt SelectListItem gt  selectList  string optionLabel  IDictionary lt string  object gt  htmlAttributes        if  expression    null                throw new ArgumentNullException  expression                ModelMetadata metadata   ModelMetadata FromLambdaExpression expression  htmlHelper ViewData          IDictionary lt string  object gt  validationAttributes   htmlHelper          GetUnobtrusiveValidationAttributes ExpressionHelper GetExpressionText expression   metadata          if  htmlAttributes    null          htmlAttributes   validationAttributes      else         htmlAttributes   htmlAttributes Concat validationAttributes  ToDictionary k   gt  k Key  v   gt  v Value          return SelectExtensions DropDownListFor htmlHelper  expression  selectList  optionLabel  htmlAttributes

User · Answer

If you have your SelectList object  just iterate through the items in it and set the  Selected  property of the item you wish   foreach  var item in selectList Items      if  item Value    selectedValue          item Selected   true      break          Or with Linq   var selected   list Where x   gt  x Value     selectedValue   First    selected Selected   true

User · Answer

I wanted the dropdown to select the matching value of the id in the action method  The trick is to set the Selected property when creating the SelectListItem Collection  It would not work any other way  perhaps I missed something but in end  it is more elegant in my option   You can write any method that returns a boolean to set the Selected value based on your requirements  in my case I used the existing Equal Method  public ActionResult History long id                        var app   new AppLogic                var historyVM   new ActivityHistoryViewModel                 historyVM ProcessHistory   app GetActivity id               historyVM Process   app GetProcess id               var processlist   app GetProcessList                 historyVM ProcessList   from process in processlist                                     select new SelectListItem                                                                               Text   process ProcessName                                          Value   process ID ToString                                            Selected   long Equals process ID  id                                                                                           var listitems   new List lt SelectListItem gt                  return View historyVM

User · Answer

I usually use this method          public static SelectList SetSelectedValue SelectList list  string value                if  value    null                        var selected   list Where x   gt  x Value    value  First                selected Selected   true              return list                    return list

User · Answer

You can use below method  which is quite simple   new SelectList items   ID    Name  items Select x  gt  x Id  FirstOrDefault       This will auto-select the first item in your list  You can modify the above query by adding a where clause

User · Answer

Further to  Womp answer  it s worth noting that the  Where  Can be dropped  and the predicate can be put into the  First  call directly  like this   list First x   gt  x Value     selectedValue   Selected   true

User · Answer

I needed a dropdown in a editable grid myself with preselected dropdown values  Afaik  the selectlist data is provided by the controller to the view  so it is created before the view consumes it  Once the view consumes the SelectList  I hand it over to a custom helper that uses the standard DropDownList helper  So  a fairly light solution imo  Guess it fits in the ASP Net MVC spirit at the time of writing  when not happy roll your own     public static string DropDownListEx this HtmlHelper helper  string name  SelectList selectList  object selectedValue        return helper DropDownList name  new SelectList selectList Items  selectList DataValueField  selectList DataTextField  selectedValue

[c#] MVC - Set selected value of SelectList

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