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

Answer 1

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:

<configuration>
    <system.web.webPages.razor>
        <pages>
            <namespaces>
                <add namespace="System.Linq" />
            </namespaces>
        </pages>
    </system.web.webPages.razor>
</configuration>

Answer 2

I had this issue , When calling Generic.List like:

mylist.Select( selectFunc )

Where selectFunc is defined as Expression<Func<T, List<string>>>. Simply changed "mylist" to be a IQuerable instead of List then it allowed me to use .Select.

Answer 3

Just add this namespace,

using System.Linq;

Answer 4

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<string> = GrabDataFromDBByID(ViewBag.id).Select(a=>a.ToString());

The above code will lead to an error in this part: .Select(a=>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.