Up until now, we have covered a lot of ground related to our Blazor WebAssembly application. But, we still have to cover the handling of PUT and DELETE actions in the same application. Additionally, we want to ask our users if they are sure about the Delete action. So, for that, we are going to show you how to call JavaScript functions in Blazor WebAssembly and implement a confirmation window.

To download the source code for this article, you can visit the Calling JS Functions in Blazor WebAssembly repository.

For the complete navigation for this series, you can visit the Blazor Series page.

We are going to divide this article into the following topics:

Implementing the GetProduct Action in Web API

Before we start with the PUT and DELETE actions, we have to implement an additional action on the Web API’s side. So, let’s start with the IProductRepository interface modification:

Right after that, we are going to modify the ProductRepository class:

Now, let’s create the GetProduct action in the Products controller:

That’s it. Feel free to test this to make sure it’s working as expected.

Handling the PUT Request in Blazor WebAssembly and Web API

Let’s start with the server-side implementation.

First, we need to modify the IProductRepository interface:

Then, let’s modify the ProductRepository class:

Pay attention that we didn’t want to make the logic more complicated by using AutoMapper, but we strongly recommend using it for the mapping actions. To read more on how to use the AutoMapper library in the ASP.NET Core application, you can read our Getting Started with AutoMapper article.

Additionally, if you are confused why don’t we use the Update method from the _context object, we strongly recommend reading our EntityFramework Core series or just Modifying Data with EF Core article that is strictly related to this topic.

The last step for the server-side implementation is to create a new UpdateProduct action in the Products controller:

For additional information and a deep-dive guide about how to handle the PUT action in ASP.NET Core Web API, please read our article on this topic.
These articles will provide a lot more insights about handling the PUT and all the other requests in ASP.NET Core Web API.

Now, let’s test this:

Update postman

We can see the update is successful. And if we check the logs, we can see that only the price was updated because we changed only that property:

Update EF Core log

Excellent. Now let’s continue with the Blazor WebAssembly part.

The Client-Side implementation

The first thing we are going to do is to add a new method signature in the IProductHttpRepository interface:

Next, let’s modify the ProductHttpRepository class:

As you can see, these are pretty straight forward methods and there is nothing we haven’t seen in the previous articles of this series.

Now, let’s create the UpdateProduct component files in the Pages folder.

We are going to modify the class file first:

We can see one important difference from the CreateProduct component and that’s the OnInitializedAsync method. By calling it, as soon as our component initializes, we call the GetProduct method from the repository class and populate our _product variable. We have to populate the _product object to assign values to our controls on the Update form. The Update method will trigger as soon as we click the submit button on the form and the AssignImageUrl will do exactly that if we change the product’s picture.

After the class modification, let’s modify the razor file:

So, we use the @page directive to create a route to this page. We can see that this route has an id parameter. This parameter will be automatically assigned to the Id parameter in the class file. Once the _product parameter is populated, we generate the form controls. We use again the EditForm component but this time we pass the Update method for the OnValidSubmit event emitter. The controls are the same as in the CreateProduct form except for the ImageUpload component, where we pass the image url as well because we already have that information.

Finally, to be able to navigate to this page, we have to modify the ProductTable component file:

And the class file:

We just inject the NavigationManager service to be able to navigate to the required page. We’ve learned about this service in the Routing Part of this series.

Testing the Update Actions

Now, let’s start both server and client applications and navigate to the Products page. Then, we can click the update button and see all the fields populated:

Blazor WebAssembly Update form

Let’s change the price field to 36 and click the Update button:

Update success


Once we click the close button, we can see our product with the updated price:

Product updated price

So, as we can see, everything is working like a charm.

Now, we can continue with the Delete action.

Delete Action – Web API

Let’s start with the IProductRepository interface modification:

Then, let’s implement this method in the repository class:

And finally, let’s modify controller:

That’s all it takes. Let’s move on to the client side.

Delete Action – Blazor WebAssembly

Let’s start with the IProductHttpRepository interface modification:

And let’s continue with the ProductHttpRepository class:

Now, in the ProductTable class file, we are going to add a new parameter:

And to invoke it in the ProductTable component file:

This means that in the parent component, we need to have a method connected to this event callback parameter. So, let’s create it in the Products class file:

And of course, we have to modify the Products.razor file:

If we try to delete any product at this moment, we will be able to do it. But, we don’t want to allow users to delete a product just like that. We want them to confirm their decision. For that, we could create another modal component and use it, but in this case, we are going to show you how to use the JavaScript’s confirmation dialog.

JavaScript Functions in Blazor WebAssembly

Using JavaScript functions in Blazor WebAssembly is pretty easy because we have the IJSRuntime service that helps us in the process. By injecting it into the component, we can invoke the JavaScript functions in Blazor WebAssembly. Basically, it represents an instance of a JavaScript runtime to which calls may be dispatched.

Now, let’s see how to use this service in practice.

We are going to start with the ProductTable class file, by injecting the IJSRuntime service:

And adding a new method:

We extract the product by its id property from the local Products list. Then, we use the Js property and the InvokeAsync method to call the confirm JavaScript function and pass a parameter to that function. If a user confirms the delete action, we invoke our event callback parameter and execute the method from the parent component.

Now, all we have to do is to modify the @onclick event on the Delete button in the razor file:

After these changes, we can test our result:

Delete with confirmation - JavaScript Functions in Blazor WebAssembly

As we can see, we can remove our product only if we confirm our decision.

Great job.


In this article, we have learned how to handle the PUT and DELETE requests on both Web API and Blazor WebAssembly sides. Additionally, we have learned how to use the IJSRuntime service to invoke JavaScript functions in Blazor WebAssembly applications.

We hope you enjoyed and learned a lot from this article and this series overall.

In the next article, we are going to learn about AuthenticationStateProvider in Blazor WebAssembly and how to use it for the authentication actions.