Ensuring that a parameter is required

The EditorRequired attribute indicates to your IDE that passing data to the component is functionally critical. This attribute triggers data validation at compile time, creating a quick feedback loop and enhancing code quality. Utilizing the EditorRequired attribute ensures neither you nor anyone from your team will fall into errors due to missing parameters. You can simplify your code by skipping initial parameter value validation. Using the EditorRequired attribute leads to robust and predictable component behavior throughout the application.

Let’s enhance the Ticket component parameters so that Blazor treats them as required. You’ll also learn how to configure your IDE so that you can flag any missing required parameters as compilation errors.

Getting ready

Before setting up the required parameters, do the following:

• Create a Recipe05 directory – this will be your working directory
• Copy the Ticket and Offer components from the previous recipe or copy their implementation from the Chapter01/Recipe04 directory of this book’s GitHub repository

How to do it...

Ensure parameters are required in your component by following these steps:

1. Navigate to the @code block of the Ticket component and extend attribute collection on parameters with the EditorRequired attribute:

   @code {
       [Parameter, EditorRequired]
       public string Tariff { get; set; }
       [Parameter, EditorRequired]
       public decimal Price { get; set; }
       [Parameter]
       public EventCallback OnAdded { get; set; }
   }

2. Now, navigate to the .csproj file of the project where you’re keeping your components.
3. Add the RZ2012 code to the WarningsAsErrors section:

   <Project Sdk="Microsoft.NET.Sdk.Web">
     <PropertyGroup>
       <TargetFramework>net9.0</TargetFramework>
       <ImplicitUsings>enable</ImplicitUsings>
       <WarningsAsErrors>RZ2012</WarningsAsErrors>
     </PropertyGroup>
     <!-- ... -->
   </Project>

4. In the Offer markup, modify the Ticket instances by removing the OnAdded parameter from both. Additionally, remove the Price parameter from the second instance:

   <Ticket Tariff="Adult" Price="10.00m" />
   <Ticket Tariff="Child" />

5. Compile your application so that you can see your IDE flagging the omitted but required Price parameter:

Figure 1.7: IDE flags missing the Price parameter as a compilation error

How it works...

In step 1, we enhanced the Tariff and Price parameters of the Ticket component with the EditorRequired attribute. This prompts your IDE to expect these values during compilation and flag the missing ones as warnings by default. I suggest that you raise that severity. In step 2, you navigated to the .csproj file of your project. Here, as outlined in step 3, you either found or added the WarningsAsErrors section and included the RZ2012 code within. In step 4, we broke the Offer markup a little. We removed the OnAdded parameter from both Ticket instances and the Price parameter from one of them. Now, any compilation attempt will end with an error, similar to the one shown in step 5. This makes it practically impossible to miss required assignments and encounter related rendering errors. Notice that as we didn’t mark the OnAdded parameter with the EditorRequired attribute, the compiler will treat it as optional and allow it to be skipped.