Working with Non-String Data

Currently, all of our Add action method's parameters are using the string data type. 0:00 This is a natural fit for values that are being submitted by the form, 0:05 because the field values are represented in the request body as text. 0:09 If we wanted to convert the date parameter to an actual date time value, 0:14 we could write the following code. 0:18 First, we need a DateTime variable. 0:21 Then, we can make a call to the DateTime.TryParse static method, 0:26 passing in the date parameter and our DateTime variable as an out parameter. 0:32 While this approach would work, it's a lot of extra code to write. 0:38 Fortunately, MVC's model binder will do the work for us. 0:42 All we need to do is change our parameter data types and 0:46 the model binder will automatically attempt to convert the incoming values 0:50 to the expected data types. 0:55 Let's update the date parameter to be of type DateTime, 0:57 activityId to be of type int, duration to be of type double, 1:01 intensity to be of type Entry.IntensityLevel, 1:08 which is an enum in the Entry class that defines the available intensity levels, 1:17 exclude to be of type bool, and notes can remain a string. 1:27 Go ahead and remove this bit of code, and press F5 to run our app. 1:34 This time, let's try saving the form without providing any values. 1:42 And we get an error. 1:48 The parameters dictionary contains a null entry for 1:50 parameter date of non nullable type System.DateTime. 1:53 For our method Add in our controller EntriesController, an optional parameter 1:58 must be a reference type, a nullable type, or be declared as an optional parameter. 2:03 That is a long-winded way of telling us that MVC was unable to call 2:09 our action method, because the request didn't provide a value for 2:13 the date parameter, and our action method parameter doesn't allow nulls. 2:18 To work around this issue, we need to update each of our parameters that 2:23 are using a data type that doesn't allow nulls to be nullable. 2:27 So date, activityId, duration, intensity, and 2:35 exclude all need to use the corresponding nullable types. 2:39 That's easy to do. 2:44 We just need to add a question mark after the data type. 2:45 DateTime? 2:51 Int? 2:56 Double? 2:59 IntensityLevel? 3:03 And bool?. 3:05 Let's run our app again and see if that fixed the issue. 3:09 Let's start by saving our form without providing any values. 3:14 Okay, we hit our breakpoint. 3:19 We're good so far. 3:21 Press F5 to continue. 3:23 And we're back at our form. 3:26 Let's enter values and save the form again. 3:28 1/1/2016. 3:31 1, 23, Low, False. 3:33 And this is my note. 3:39 And save the form. 3:43 If we view the Locals window, which shows all of the currently in scope variables, 3:45 we can see that our parameters have all of our provided values. 3:50 Press F5 to continue. 3:54 And all of our values, with the exception of the Exclude field, 3:57 have been redisplayed back to us. 4:01 The exclude field isn't retaining its value 4:05 because of how MVC handles rendering element attributes. 4:08 When MVC is writing a boolean value to an attribute, 4:12 it will omit the attribute if the value was false or 4:15 render the attribute name equal to the attribute name if the value was true. 4:19 We can see this in action by supplying a value of true and saving the form again. 4:25 Now the field value that is redisplayed back to us is value, 4:32 which is the name of the attribute that we're trying to set. 4:37 We can work around this issue by converting our boolean value to a string. 4:40 First, let's surround our expression with a set of parentheses. 4:59 Then we need to check if the ViewBag.Exclude property is null. 5:03 And if it isn't, call the ToString method on it. 5:07 Otherwise, we'll render an empty string. 5:13 Now, if we refresh the page, you'll see the expected behavior. 5:18 The exclude field is now set to True. 5:28 Don't worry too much about this issue and the workaround that we're using here. 5:31 Normally, you would use a check box to represent a boolean value in a form, 5:35 not a text box, which prevents this issue from even surfacing. 5:40 We'll switch to using a checkbox for the Exclude field in the next section. 5:44 Go ahead and stop the app. 5:49 If you're using GitHub, let's commit our changes. 5:53 Enter a commit message of Updated the EntriesController Add 6:00 method parameter data types and click the Commit All button. 6:07 After the break, we'll take a look at how we can use model state 6:15 to improve our handling of invalid values. 6:18