How can I reuse a DropDownList in several views with .NET MVC

Question

Several views from my project have the same dropdownlist...

So, in the ViewModel from that view I have :

public IEnumerable<SelectListItem> FooDdl { get; set; }

And in the controller I have :

var MyVM = new MyVM() {
    FooDdl = fooRepository.GetAll().ToSelectList(x => x.Id, x => x.Name)
}

So far so good... But I´m doing the same code in every view/controller that have that ddl...

Is that the best way to do that?

Thanks

Answer 1

I'd say that's fine to be honest, as it's only a repeat of a few lines of code. If it's really bothering you though, you could have all your controllers inherit from a BaseController (if they don't already) and store a method in there to get them all, something like:

public IEnumerable<SelectListItem> GetFoos()
{
    return fooRepository.GetAll().ToSelectList(x => x.Id, x => x.Name);
}

Then in your controllers you could do:

var MyVM = new MyVM() {
    FooDdl = GetFoos()
}

Answer 2

If your DropDownList is exactly the same the approach I would use is:

1) In your Base Controller or in a Helper class, you can create a method that returns a SelectList. That method should receive a nullabe int to get the select list with a value pre selected.

2) It is wise to cache the information you list in the DDL, to not query the database too often.

So, for (1):

public SelectList GetMyDDLData(int? selectedValue){
    var data = fooRepository.GetAll().Select(x => new { Value = x.Id, Text = x.Name });
    return new SelectList(data, "Id","Name", selectedValue);
}

In the view model:

var myVM = new MyVM();
myVM.DDLData = this.GetMyDDLData(null) // if it is in your BaseController.
myVM.DDLData = YourHelperClass.GetMyDDLData(null) // if it is in a helper static class

In your views:

@Html.DropDownListFor(x => x.FooProp, Model.DDLData, "Select one...")

For number (2):

private IEnumerable<YourModel> GetMyData()
{
    var dataItems = HttpContext.Cache["someKey"] as IEnumerable<YourModel>;
    if (dataItems == null)
    {
        // nothing in the cache => we perform some expensive query to fetch the result
        dataItems = fooRepository.GetAll().Select(x => new YourModel(){ Value = x.Id, Text = x.Name };

        // and we cache it so that the next time we don't need to perform the query
        HttpContext.Cache["someKey"] = dataItems ;
    }

    return dataItems;
}

The "someKey" could be something specific and static is this data is the same to all users, or you can do "someKey" + User.Id if the data is specific to one user.

If your repository is an abstractin layer (not directly EntityFramework) you can place this code there.