'object' does not contain a definition for

问题:

I had this problem once before and didn't resolve it. I have a list (generated in an MVC3 controller):

ViewBag.Languages = db.Languages
    .Select(x => new { x.Name, x.EnglishName, x.Id })
    .ToList();

and on my page (Razor) I try to iterate through it:

foreach (var o in ViewBag.Languages)
{
    string img = "Lang/" + o.EnglishName + ".png";
    @* work *@
}

but the reference to o.EnglishName fails with the error:

'object' does not contain a definition for 'EnglishName'

though the curious thing is that if I type into the Immediate Window (whilst debugging):

o
{ Name = བོད་སྐད་, EnglishName = Tibetan, Id = 31 }
    EnglishName: "Tibetan"
    Id: 31
    Name: "བོད་སྐད་"

so obviously the field is there. What is my problem here?

回答1:

You are using an anonymous object here:

ViewBag.Languages = db.Languages
    .Select(x => new { x.Name, x.EnglishName, x.Id })
    .ToList();

Anonymous objects are emitted as internal by the compiler. The Razor views are automatically compiled into a separate assembly by the ASP.NET runtime. This means that you cannot access any anonymous objects generated in your controllers.

So in order to fix your issue you could define a view model:

public class LanguageViewModel
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string EnglishName { get; set; }
}

and then in your controller use this view model:

ViewBag.Languages = db.Languages
    .Select(x => new LanguageViewModel
    { 
        Name = x.Name, 
        EnglishName = x.EnglishName, 
        Id = x.Id 
     })
    .ToList();

And now that you have a view model the next improvement to your code is of course to get rid of this crap of ViewBag that I am sick of seeing and simply use view models and strong typing:

public ActionResult Foo()
{
    var model = db
        .Languages
        .Select(x => new LanguageViewModel
        { 
            Name = x.Name, 
            EnglishName = x.EnglishName, 
            Id = x.Id 
        })
        .ToList();
    return View(model);
}

and then of course have a strongly typed view:

@model IEnumerable<LanguageViewModel>
@Html.DisplayForModel()

and then define the corresponding display template which will automatically be rendered by the ASP.NET MVC engine for each element of the view model so that you don't even need to write a single foreach in your views (~/Views/Shared/DisplayTemplates/LanguageViewModel.cshtml):

@model LanguageViewModel
... generate the image or whatever you was attempting to do in the first place

回答2:

This was driving me spare until I checked my code and found this:

class AdsViewModel
{
    public int Id { get; set; }
    public  string City { get; set; }
    public string CompanyName { get; set; }
    public string ContactName { get; set; }
    public string UserEmail { get; set; }
    public string ContactPhone { get; set; }
    public string ShortTitle { get; set; }
    public string AdUrl { get; set; }
}

Changing it to:

public class AdsViewModel 

Fixed it.

回答3:

It can happen as well if the name of your class doesn't match the name of the file (I know it's stupid but it might help you)

回答4:

Please use ViewData instead of ViewBag like.

ViewData["Lang"] = db.Languages
.Select(x => new { x.Name, x.EnglishName, x.Id })
.ToList();

Then

foreach (var o in (dynamic) ViewData["Lang"])
{
string img = "Lang/" + o.EnglishName + ".png";
@* work *@
}