c# - Blazor 将 EventCallback 作为类属性传递给组件

Question

我正在尝试在 Blazor 中开发一个组件，我希望它从 C# 类中获取所有功能(文本、EventCallbacks 等)。像这样:

Blazor 组件(代码隐藏):

public partial class Card : ComponentBase
{
    [Parameter] public CardData CardData { get; set; }

    protected async Task OnActionFiredEvent(EventCallback<object> eventCallback, object itemId)
    {
        if (eventCallback.HasDelegate)
            await CardData.CardTitleOnClickAction.InvokeAsync(itemId);
    }
}

Blazor 组件(Razor):

<!-- Card image -->
<div class="view view-cascade overlay">
    <a>
        <div class="mask rgba-white-slight waves-effect waves-light"></div>
    </a>
</div>

<!-- Card content -->
<div class="card-body card-body-cascade text-center">

    <!-- Title -->
    <h4 class="card-title">
        <a class="waves-effect waves-light" @onclick="@(() => OnActionFiredEvent(CardData.CardTitleOnClickAction, CardData.CardItemId))">
            <strong>@CardData.CardTitle</strong>
        </a>
    </h4>
    <!-- Subtitle -->
    @if (!string.IsNullOrEmpty(CardData.CardSubTitle))
    {
        <h6 class="font-weight-bold indigo-text py-2">@CardData.CardSubTitle</h6>
    }

    <!-- Text -->
    @if (!string.IsNullOrEmpty(CardData.CardText))
    {
        <p class="card-text">
            @CardData.CardText
        </p>
    }
</div>

<!-- Card footer -->
<div class="card-footer text-muted text-center">
    @CardData.CardFooter
</div>

汽车数据类:

public class CardData
{
    public object CardItemId { get; set; }
    public string CardTitle { get; set; }
    public string CardSubTitle { get; set; }
    public string CardText { get; set; }
    public string CardFooter { get; set; }
    public EventCallback<object> CardTitleOnClickAction { get; set; }
}

使用:

<Card CardData="@(new CardData() {
CardTitle = "TextTitle",
CardTitleOnClickAction = EventCallBackMethod,
CardSubTitle = "TextSubTitle",
CardText = "Text"})" />

问题是在将 EventCallBack 作为类属性传递时出现以下错误:无法将方法组“EventCallBackMethod”转换为非委托(delegate)类型“EventCallback”。您是否打算调用该方法？

失败的方法本身是这样的:

protected async Task EventCallBackMethod()
    {
        await DoSomething();
    }

知道如何解决这个问题吗？

Answer 1

正如 Brian Parker 所提到的，您需要在回调中有一个类型。如果您不想传递一个值，您可以传递 null，例如；

MyComponent.razor

<button @onclick="OnButtonClicked">Click me</button>

@code{
    [Parameter]
    public EventCallback ButtonClicked{ get; set; }


    protected async Task OnButtonClicked()
    {
        await ButtonClicked.InvokeAsync(null);
    }
}

例如作为 Razor 组件，按钮点击触发 OnButtonClicked，然后调用 ButtonClicked 参数，可以在父页面中引用该参数。

Page.razor

@page "/pagename"

<MyComponent ButtonClicked="@ButtonClickedHandler" />

@code{
    protected void ButtonClickedHandler()
    {
        Logger.LogInfo("Button click was handled on the page");
    }
}

---

如果你想传递参数你可以这样做;

MyNextComponent.razor

<button @onclick="OnButtonClicked">Click me</button>

@code{
    [Parameter]
    public EventCallback<bool> ButtonClicked{ get; set; }

    protected async Task OnButtonClicked(bool value)
    {
        await ButtonClicked.InvokeAsync(true);
    }
}

Page.razor@page "/页面名称"

<MyNextComponent ButtonClicked="@ButtonClickedHandler" />

@code{
    protected void ButtonClickedHandler(bool value)
    {
        Logger.LogInfo($"Button click was handled on the page: {value}");
    }
}