C#Blazor WebAssembly：参数2：无法从&#39；void&#39；转换为&#39；Microsoft.AspNetCore.Components.EventCallback&#39； [英] C# Blazor WebAssembly: Argument 2: cannot convert from 'void' to 'Microsoft.AspNetCore.Components.EventCallback'

问题描述

我是Blazor C#的新手，正在尝试创建一个简单的倒计时计时器网站。我的网站包括：

• 显示计时器的文本
• 启动和停止按钮
• 设置计时器的按钮

设置计时器的按钮有问题。当我点击它时，它不会设置计时器显示，我得到一个错误Argument 2: cannot convert from 'void' to 'Microsoft.AspNetCore.Components.EventCallback'。我在YouTube上搜索EventCallback主题，但问题是，我的组件没有分开，而在视频中，示例代码将分开的组件链接在一起。以下是代码。
索引.razor

@page "/"
@inherits FrontEnd.Components.Timer

<h1>Timer</h1>

<p class="timer">@Hours.ToString("00"):@Minutes.ToString("00"):@Seconds.ToString("00")</p>
@foreach (var timer in timerCollections)
{
    // Here's the problem
    <button @onclick="SetTimer(timer.Id)">@timer.Hours.ToString("00"):@timer.Minutes.ToString("00"):@timer.Seconds.ToString("00")</button>
}
<br/>
<button @onclick="StartTimer" disabled=@StartButtonIsDisabled>Start</button>
<button @onclick="StopTimer" disabled=@StopButtonIsDisabled>Stop</button>

Timer.cs

using System;
using System.Timers;
using System.Collections.Generic;
using Microsoft.AspNetCore.Components;

namespace FrontEnd.Components
{
    public class TimerStructure
    {
        public int Id { get; set; }
        public int Hours { get; set; }
        public int Minutes { get; set; }
        public int Seconds { get; set; }      
    }
    public class Timer : ComponentBase
    {
        public List<TimerStructure> timerCollections = new List<TimerStructure>(){
            new TimerStructure(){ Id = 1, Hours = 0, Minutes = 30, Seconds = 0 },
            new TimerStructure(){ Id = 2, Hours = 1, Minutes = 0, Seconds = 0 }
        };

        public int Index { get; private set; }
        public int Hours { get; set; } = 0;
        public int Minutes { get; set; } = 0;
        public int Seconds { get; set; } = 0;
        public bool StopButtonIsDisabled { get; set; } = true;
        public bool StartButtonIsDisabled { get; set; } = false;
        private static System.Timers.Timer aTimer;
        // and this is the function related to the problem
        public void SetTimer(int value)
        {
            this.Index = value - 1;
            Hours = timerCollections[Index].Hours;
            Minutes = timerCollections[Index].Minutes;
            Seconds = timerCollections[Index].Seconds;
        }
        public void StopTimer()
        {
            aTimer.Stop();
            aTimer.Dispose();

            StopButtonIsDisabled = true;
            StartButtonIsDisabled = false;

            Console.WriteLine($"{Hours}:{Minutes}:{Seconds}");
        }
        public void StartTimer() 
        {
            aTimer = new System.Timers.Timer(1000);
            aTimer.Elapsed += CountDownTimer;
            aTimer.Start(); 

            StopButtonIsDisabled = false;   
            StartButtonIsDisabled = true;
        }
        public void CountDownTimer(Object source, ElapsedEventArgs e)
        {
            if(Seconds == 0 && Minutes > 0)
            {
                Minutes -= 1;
                Seconds = 59;
            } else if (Minutes == 0 && Seconds == 0 && Hours > 0)
            {
                Hours -= 1;
                Minutes = 59;
                Seconds = 59;
            } else if (Hours == 0 && Minutes == 0 && Seconds == 0)
            {
                aTimer.Stop();
                aTimer.Dispose();

                StopButtonIsDisabled = true;
                StartButtonIsDisabled = false;
            } else
            {
                Seconds -= 1;
            }
            InvokeAsync(StateHasChanged);
        }
    }
}

推荐答案

尝试：<button @onclick="() => SetTimer(timer.Id)">

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