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Using Action Result Types
7:31Returning a string literal from a controller action method is unusual. An action method typically returns one of the MVC action result types. Let’s see how to do that.
Returning a string literal from
a controller action method is unusual.
0:00
An action method typically returns
one of the Mvc action result types.
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Let's start by replacing our string
literal with a content result object.
0:10
Content result is an action
result type provided by Mvc.
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Just above our existing return statement,
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let's return an instance of
the content result class.
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Since we're no longer returning a string,
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we'll need to change our methods
return type to content result.
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We can use the ContentResult content
property to set our content.
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To do that,
let's add a set of curly braces
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to the right of the ContentResult
constructor call.
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In between the curly braces,
type the property name Content
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followed by an equal
sign in a pair of quotes.
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Then let's cut and
paste our string literal from here
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to there and
remove the extra return statement.
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Let's run our website by pressing F5 and
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verify that everything is
still working correctly.
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Remember even though we replaced our
string literal with a content result
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object, we still expect our detail action
method to return the same content.
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Don't forget we need to browse
to the URL ComicBooks/Detail.
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Great, we [LAUGH] didn't break anything.
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Go ahead and close Chrome.
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Stop the website and
hide the output window.
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Content result is just one of the action
result types that NVC provides.
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Another action result type,
redirect result,
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is used to redirect
the user to another URL.
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Let's add an if statement that
will redirect the user to the home
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page if today is Monday.
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We can use the DateTime.Today static
property to get a date time for today.
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On that object there's
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a DayOfWeek property that we can
use to check if today is Monday.
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To do that we just compare
the property value
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to the DayOfWeek.Monday enumeration value.
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In a later course we'll cover in more
detail how to work with dates and
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times in C#.
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If you'd like to learn more now,
see the teacher's note for
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links to additional resources.
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Okay, inside the if statement,
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let's return a new instance
of the redirect result class.
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In the constructor,
let's pass the string literal /,
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which represents the root of our website.
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Hm.
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There's a problem with our code.
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If we hover our mouse pointer
over the offending code,
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we can see the error message.
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Cannot implicitly convert type
System.Web.Mvc.RedirectResult
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to System.Web.Mvc.ContentResult.
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Looks like the compiler was
unable to implicitly convert
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the redirect result type to our
methods content result type.
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We can try explicitly casting the redirect
result object to content result
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by typing a set of parenthesis
containing the type content result.
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But that doesn't work either.
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Cannot convert type,
RedirectResult to ContentResult.
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To resolve this issue, we need a type that
isn't common to both of our result types.
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Let's go to the definition for
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RedirectResult by putting the cursor
on the constructor and pressing F12.
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Since the RedirectResult
class is part of Mvc and
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we don't have the source
code in our solution,
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Visual Studio will only display the basic
information for the public class members.
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For our purposes,
that will work just fine.
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We can see that the base
class is ActionResult.
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Let's go back to our controller and
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put our cursor on
the ContentResult constructor.
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This time let's hold down
the alt key when pressing F12.
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This allows us to peek the definition
in line with our code.
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If we scroll up a bit in the peek window,
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we can see that the base
class is also ActionResult.
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So redirect result and
content result have a common base class.
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Let's close the peek window and change
our methods return type to ActionResult.
4:19
Problem solved all of the Mvc ActionResult
types share the action result base
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class because of this action result is
almost always used as the return type for
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action methods.
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Regardless of the specific ActionResult
type that is being returned.
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Remember the Mvc Controller base
class that we're inheriting from?
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The Controller base class
provides a number of methods
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that can help simplify our code.
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We can replace our ContentResult object
with a call to the Content method,
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which accepts a string for the content.
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We can also replace our redirect result
object with a call to the Redirect
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method which accepts a string for
the target URL.
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Let's run our website and
test our changes.
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Don't forget to browse
to ComicBooks/Detail.
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Good, we're still seeing our content.
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Next let's stop the website and
update our if statement, so
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that we can test our call
to the Redirect method.
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I'm recording this video on a Tuesday.
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So I'll update the day
of the week to Tuesday.
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Restart the website by pressing F5.
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When Chrome is finished loading,
browse to ComicBooks/detail.
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Excellent, notice here in the address
bar that we've been redirected
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to the root of our website.
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Which is still returning a 404 Error,
go ahead and stop the website.
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If you're using GitHub
let's commit our changes.
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Enter a commit message
of Updated Detail action
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method to use action result types and
click the Commit All button.
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We've done a number of local commits so
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now would be a good time
to sync with remote server.
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Click Sync here in this
confirmation message
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to navigate to the synchronization panel.
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Here's a list of our local commits
in the outgoing commit section.
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Click the Push link to push
these commits to the server.
6:43
Okay, we're making progress.
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But we're still returning a string for
our content.
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It's worth noting that we're not limited
to returning just a plain string.
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We could update our content
result to include HTML Markup.
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But our controller shouldn't be concerned
with the presentation of our content.
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As we discussed in an earlier video,
controllers are coordinators.
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They're responsible for
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coordinating the specific actions
that need to be performed.
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In order to return a response for
that user request.
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Presenting content is a job
better suited for a view.
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So, how do we return a view?
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In the next section,
we'll add our first view.
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See you see then.
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