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ASP.NET MVC Forms

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Completing the “Activity” Field Drop Down List

4:33 with James Churchill

Now that we’ve seen how to work with drop down lists, let’s wrap up work on the “Activity” field.

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Additional Learning

If you want to learn more about dynamic types in C# or need a refresher, see this page on MSDN.

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    Now that we've seen some examples of how to create items for 0:00
    the drop down list for method using temporary data, 0:03
    let's work on the actual implementation by updating our action methods. 0:06
    I'll add a property on the ViewBag object ActivitiesSelectListItems 0:12
    and set it to an instance of SelectList. 0:18
    Passing in the Data.Data.Activites, 0:22
    static collection. 0:28
    And the names of the properties for the value, And text fields. 0:31
    This looks odd, but it's correct. 0:40
    The first Data is the namespace for our data static class. 0:43
    Let's also remove this line of code that's setting the ActivityId property. 0:47
    Drop down list items don't automatically repopulate on a post back, so 0:53
    we also need to set this ViewBag property in our post action method. 0:57
    I'll just copy and paste this line of code from here. 1:01
    Down to here. 1:11
    And I'll remove our line of code that is setting the entry.ActivityId property. 1:12
    Now, let's update our view. 1:18
    To start with, we can remove all of this temporary code. 1:20
    Then we just need to update our call to the DropDownListFor 1:30
    method to use our new ViewBag property. 1:36
    ViewBag.ActivitiesSelectListItems. 1:40
    The only thing that's tricky here is that we need to explicitly cast 1:49
    the ViewBag property to its actual type of select list. 1:53
    That's necessary because ViewBag is a dynamic object. 1:57
    Let's run our app and test our changes. 2:05
    And here's our list of available activities. 2:11
    What if we wanted to insert an empty item as the first item so 2:16
    users would need to select a value? 2:20
    Turns out, there's a method overload that makes this easy to do. 2:22
    We can add an empty string, just after the SelectList parameter, and 2:27
    the DropdownListFor method will create a default empty item. 2:31
    We could supply a prompt for our value. 2:39
    Something like Select an Activity, but I prefer to use an empty string. 2:42
    Also it's worth noting that if you pass in null for 2:48
    the value, MVC won't create the default empty item. 2:51
    You need to pass a string value, save the view, and refresh the page. 2:55
    And now the empty item is selected by default, 3:01
    if we right-click on the drop-down list and 3:04
    select the inspect menu item, we can see what our controls markup looks like. 3:06
    The first option is our default empty item. 3:13
    The remaining items are the available activities that we can select from. 3:19
    The value attributes represent the activity ID values, and 3:23
    the option element inner text is populated with the activity name values. 3:27
    When the form is submitted to the server, the selected items value attribute, 3:33
    is used for the activity ID form fields value. 3:37
    It's worth noting, that when we save an entry, 3:40
    we only have the activity ID value on hand, not the activities name. 3:43
    We don't need the activity name, until we display the entry on the list page. 3:48
    This might be surprising the first time you see this approach in use. 3:53
    But it's a very common way of handling related data. 3:56
    Go ahead and stop the app. 4:00
    If you're using GitHub let's commit our changes. 4:03
    Enter a commit message of, 4:10
    Updated the "Activity" field to use a drop 4:13
    down list, and click the Commit All button. 4:18
    In the next video, we'll continue with improving our form 4:26
    by updating the intensity field to use radio buttons. 4:29

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