Error in Define Blazor Component Parameter

Question

[Parameter]
public object Selected
{
    get => BindObject;
    set
    {
        if (BindObject == value)
            return;
        BindObject = value;
        SelectedChanged.InvokeAsync(BindObject);
        
    }
}

[Parameter]
public EventCallback<object> SelectedChanged { get; set; }

In use:

<MyComponent @bind-Selected="person" />

Error CS1503
Argument 2: cannot convert from 'Microsoft.AspNetCore.Components.EventCallback<CustomBlazorComponents.Components.Pages.Home.Person>' to 'Microsoft.AspNetCore.Components.EventCallback'

How do I have an EventCallback (for two-way binding) of type object?

Answer 1

You intent is not obvious, but it's unlikely the best way to approach your problem is with an object.

Here's a refactored version of your code that demonstrates how to use generics in a component. I've used input for demo purposes to show how the bind works.

MyComponent

@typeparam TType
<h3>MyComponent</h3>

<input @bind:get="Selected" @bind:set="OnSet"/>

@code {
    [Parameter] public TType? Selected { get; set; }
    [Parameter] public EventCallback<TType?> SelectedChanged { get; set; }

    private async Task OnSet(TType? value)
    {
        await this.SelectedChanged.InvokeAsync(value);
    }
}

Home

@page "/"

<PageTitle>Home</PageTitle>

<h1>Hello, world!</h1>

<MyComponent @bind-Selected="_value" />

<div class="bg-dark text-white m-2 p-2">
    <pre>@_value</pre>
</div>

@code{
    private string _value = "Fred";
}