Error Boundaries in Blazor

-
Error Boundaries in Blazor

This blog is going to explain what is Error Boundary in Blazor and how to implement it in the application. The Error Boundary is an easy way to handle the exception. If there is no error it will render the content, otherwise it will display the error message. Wrapping error Error Boundary component around the content will handle the unhandled exception.

Let’s see this with an example.

The following is the Index.razor page. Here I have added the Counter component covered by the <ErrorBoundary> component.

Index.razor
@page "/"
 
<PageTitle>Index</PageTitle>
 
<h1>Hello, world!</h1>
 
Welcome to your new app.
 
<SurveyPrompt Title="How is Blazor working for you?" />
 
<ErrorBoundary>
<Counter />
</ErrorBoundary>

To demonstrate the error handling process. I have modified the existing IncrementCount() as follows. So when the user clicks the click me button it will throw out the exception.

private void IncrementCount()
{
  throw new Exception("Error Boundary Demo.");
}

The following image is the output of the code above. Here you can see that when the user clicks the button it shows an error message.

Error Boundaries in Blazor
Note:
The error message and alert icon comes from the default Balzor template.
You can change it to wwwroot\css\site.css file if you wish.

Custom Error Message

You can customize the error message using the Error Boundary. See the code snippets below. Two more components <ChildContent> and <ErrorContent> are added here. You can write your custom error message within <ErrorContent>.

<ErrorBoundary>
    <ChildContent>
        <Counter />
    </ChildContent>
    <ErrorContent>
        <div class="alert alert-danger">
            Oh No... There is an error...
        </div>
    </ErrorContent>
</ErrorBoundary>

The following image is an output of the above code.

Error Boundaries in Blazor

Also, you can catch the exact and detailed error using the context attribute of the ErrorBoundary component. In the below code snippets the Context=ex is added in the ErrorBoundary component.Therefore, it will display exception details.

<ErrorBoundary Context=ex>
    <ChildContent>
        <Counter />
    </ChildContent>
    <ErrorContent>
        <div class="alert alert-danger">
            Oh No... There is an error...
        </div>
        <div class="blazor-error-boundary">
           <div>@ex.Message</div>
           <div>@ex</div>
        </div>
    </ErrorContent>
</ErrorBoundary>

The below image is an output of the above code. It shows the complete error details.

Error Boundaries in Blazor

Error Boundary Recover Method

To set the non-error state, you can reset the status using the Recovery() method. For example, if an error occurs, the application will display the error. If the user fixes the error it will still show the error. To go non-error, you can use the Recover() method.

<ErrorBoundary Context=ex @ref="errorBoundary">
    <ChildContent>
        <Counter />
    </ChildContent>
    <ErrorContent>
        <div class="alert alert-danger">
            Oh No... There is an error...
        </div>
        <div class="blazor-error-boundary">
           <div>@ex.Message</div>
           <div>@ex</div>          
        </div>
        <div>
            <button class="btn btn-primary" @onclick="()=>errorBoundary?.Recover()">Recover</button>
        </div>
    </ErrorContent>
</ErrorBoundary>
 
@code {
    private ErrorBoundary? errorBoundary;
}

The image below is the output of the code snippet above. After clicking the Click me, the application displays an error message. After the user clicks the Recovery button, the application will move to an non-error state.

Error Boundaries in Blazor

I hope this helps you. Keep coding.

Comments

Post a Comment

Popular posts from this blog

Entity Framework Core (EF) with SQL Server LocalDB

-
Image
This blog is going to illustrate how to implement Entity Framework (EF) Core with SQL Server LocalDB. The Entity Framework Core enables access to data from the database. This allows developers to avoid having to write most of the data access code. And the SQL Server LocalDB works similarly to the SQL SERVER with few features. You can get the LocalDB when you install visual studio or visual studio express. You can find the .mdf and _log.ldf files in the C:/Users/{user} directory. Let see how to create a SQL Server LocalDB and implement Entity Framework Core Step 1: The first step is to add a connection. In the menu -> click Tools and select Connect to Database It will display the Add Connection window. Enter (localdb)\mssqllocaldb in the server name textbox. Then in the Select or enter a database, select master and click ok Now in the server explorer, you can find the master DB containing Tables, Views, Stored
Read more

SignalR with JavaScript in ASP.NET Core MVC

-
Image
This blog is going to explain what is SignalR and how to implement it in ASP.NET Core. SignalR is a real time application framework for ASP.NET Core. Using SignalR you can provide updated information without refreshing the page, for example poll results, game score, chat etc. Let's see how to achieve it in ASP.NET Core MVC. Step 1: First step I added the SignalR client library. To add a SignalR client library, Right click on the project in Solution Explorer and Add -> Client-Side Library. Select the provider as unpkg as shown in the image below. Enter the latest version of SignalR into the library. And selected signalr.js and signalr.min.js files. Finally clicked the install button to install the client library. Step 2: At this step I have created a VoteHub.cs class inside the Hubs folder(create a new folder called Hubs). This class inherits from the Hub class which is a base class of SignalR hub. The SendMessage method will be called by the connected client.
Read more

Localization in ASP.NET Core MVC with Example

-
Image
Using Query Strings for Request Culture and Simplifying Localization with IStringLocalizer Interface Let’s see how to implement Localization in ASP.NET Core MVC. In the first example, I am going to use the IStringLocalizer Interface in the controller to implement Localization. Additionally, when the user passes the desired language through the query string, it will display content in that language. First, let’s configure the settings in the program.cs file. builder.Services.AddLocalization(options => options.ResourcesPath = "Resources");  The AddLocalization method adds the localization service to the service container. I have added the supported cultures here. I have added two cultures: en for English and nl for Dutch. In the RequestCultureProviders , I have included QueryStringRequestCultureProvider() . This allows the system to determine the culture information from the query string. UseRequestLocalization initializes a RequestLocalizationOptions objec
Read more