如何从子组件向父组件传递事件更改

Question

我试图跟随“捕获对元素的引用”，将更改从子组件传递到父组件，但它不起作用，url是https://docs.microsoft.com/en-us/aspnet/core/blazor/javascript-interop?view=aspnetcore-3.0#capture-references-to-elements

能帮我个忙吗？a)代码中有什么错误吗？b)在哪里可以找到"Console.WriteLine“信息，因为我在vs输出窗口中找不到它。

1. ParentComponent.razor

@page "/parentcomponent"
@using BlazorApp.Components

<h1>Parent Component</h1>

<p>ParentYear: @ParentYear</p>

<ChildComponent @ref="ChildComponent1" @bind-Year="ParentYear" />

@code {
    private int ParentYear = 1978;

    ChildComponent ChildComponent1 = new ChildComponent();

    protected override void OnInitialized()
    {
        ChildComponent1.YearChanged += ChildFiredEvent;
    }

    public void ChildFiredEvent(int _year)
    {
        ParentYear = _year;
        Console.WriteLine(ParentYear.ToString());
        StateHasChanged();
    }

}

2. Childcomponent.razor

<h2>Child Component</h2>

<p>ChildYear: @Year</p>

<button class="btn btn-primary" @onclick="ChangeTheYear">Change Year to 1986</button>

@code {
    [Parameter]
    public int Year { get; set; }

    [Parameter]
    public Action<int> YearChanged { get; set; }

    private void ChangeTheYear()
    {
        Year = 1986;
        YearChanged?.Invoke(Year);
    }
}

Answer 1

在子组件中，YearChanged声明应如下所示：

public EventCallBack<int> YearChanged { get; set; }

然后像这样调用它：

await YearChanged.InvokeAsync(newValue);

Answer 2

非常感谢，Samer和David。我相信我使用了之前的blazor方法。现在，它与@ref一起工作得很好。干杯！以下是代码。

@page "/parentcomponent"
@using BlazorApp.Components

<h1>Parent Component</h1>

<p>ParentYear: @ParentYear</p>

<ChildComponent @ref="ChildComponent1" @bind-Year="ParentYear" />

@code {
    private int ParentYear = 1978;

    ChildComponent ChildComponent1 = new ChildComponent();
}

<p>ChildYear: @Year</p>

<button class="btn btn-primary" @onclick="ChangeTheYear">Change Year to 1986</button>

@code {
    [Parameter]
    public int Year { get; set; }

    [Parameter]
    public Microsoft.AspNetCore.Components.EventCallback<int> YearChanged { get; set; }
    enter code here
    private void ChangeTheYear()
    {
        Year = 1986;
        YearChanged.InvokeAsync(Year);
    }
}