How to use alert(),confirm() and prompt() function using Blazor?

Question

I am learning the Blazor technology. I started a default increment project in VS 2019 and I have modified the code for Decrement with confirm() and alert but it does not work.

 @page "/counter"

<h1>Counter</h1>

<p>Current count: @currentCount</p>

<button class="btn btn-primary" @onclick="IncrementCount">Increment</button>
<button class="btn btn-primary btn-danger" onclick="if (confirm('Are you sure to Decrement')) { @DecrementCount() }">Decrement</button>

@code {
    private int currentCount = 0;

    private void IncrementCount()
    {
        currentCount++;
    }

    private void DecrementCount()
    {
        currentCount--;
        // alert('Operation Successfully executed')
    }
}

In my code snippet confirm() function works perfectly but I want to call a Decrement function is not working build failed. And I would like to add a success message in my function. Please provide any option instead of using confirm(),alert() functions.

Solution

Unfortunately, there is not implementation of such useful functions in Blazor yet.
So you need to use JSRuntime instance.

@inject IJSRuntime JsRuntime

...

@code
{
    //...

    await JsRuntime.InvokeVoidAsync("alert", "Warning!"); // Alert

    bool confirmed = await JsRuntime.InvokeAsync<bool>("confirm", "Are you sure?"); // Confirm
    string prompted = await JsRuntime.InvokeAsync<string>("prompt", "Take some input:"); // Prompt

    //...
}

It makes possible to execute JS code right inside your C# code. With that you can use any JS logic you want to create behaviour you need.

See docs for details.

Comments

[devbf]

For Blazor users with no former JavaScript knowledge: Besides confirm(), JavaScript also offers the methods alert() to show a message and a OK button and prompt() (which asks the user to input some text).