System Collections Generic List does not contain a definition for Select

Question

This error is happening in many of the files in my  Views  folder       System Collection GenericList  does not contain a   definition for  Select  accepting a first argument of type    System Collections GenericList  could be found  are you   missing a using directive or an assembly reference     I ve tried adding a bunch of  using System     and other basic libraries near the top of the file but adding those do not seem to help any   This is where the error occurs for me is in the line that starts with  BindTo Model Users Select o   gt  o UserName     Any help would be greatly appreciated  Thanks     lt div id  editRolesContainer  class  detailContainer detailContainer4  gt       lt header class  sectionheader  gt  Add Roles  lt  header gt       lt ul id    AdminSelectUserContainer   gt          lt li gt             lt ul style  padding  0 0 0 5px  gt                lt li gt Select User    lt  li gt                lt li gt                   using  Html BeginForm  srch GetUserRoles    Admin                      new   view    Users Roles     FormMethod Post                     new   name    srch GetUserRoles                                             Html Telerik   AutoComplete                              Name  acx SelectUser                              BindTo Model Users Select o   gt  o UserName                                  HtmlAttributes new   type  submit                                  HtmlAttributes new    class    SearchBox                               AutoFill true                             Filterable  filtering   gt                                                                   filtering FilterMode AutoCompleteFilterMode Contains                                                                                         lt  li gt               lt  ul gt                                            lt  div gt

User · Answer

This question s bit old  but  there s a tricky scenario which also leads to this error   In controller   ViewBag id     id from querystring List lt string gt    GrabDataFromDBByID ViewBag id  Select a  gt a ToString       The above code will lead to an error in this part   Select a  gt a ToString    because of the below reason  You re passing a ViewBag id to a method which in compiler  it doesn t know the type  so there might be several methods with the same name and different parameters let s say   GrabDataFromDBByID string  GrabDataFromDBByID int  GrabDataFromDBByID whateverType    So to prevent this case  either explicitly cast the ViewBag or create another variable storing it

User · Answer

You need to have the System Linq namespace included in your view since Select is an extension method  You have a couple of options on how to do this   Add  using System Linq to the top of your cshtml file   If you find that you will be using this namespace often in many of your views  you can do this for all views by modifying the web config inside of your Views folder  not the one at the root   You should see a pages namespace XML element  create a new add child that adds System Linq  Here is an example    lt configuration gt       lt system web webPages razor gt           lt pages gt               lt namespaces gt                   lt add namespace  System Linq    gt               lt  namespaces gt           lt  pages gt       lt  system web webPages razor gt   lt  configuration gt

User · Answer

Just add this namespace   using System Linq

User · Answer

I had this issue   When calling Generic List like   mylist Select  selectFunc     Where selectFunc is defined as Expression lt Func lt T  List lt string gt  gt  gt   Simply changed  mylist  to be a IQuerable instead of List then it allowed me to use  Select

[c#] System.Collections.Generic.List does not contain a definition for 'Select'

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