在Blazor组件中初始化对象

Question

有了这个Blazor组件：

@page "/counter"

<h1>Counter</h1>

<p>Current count: @_a.CurrentCount</p>

<button class="btn btn-primary" onclick="@_b.IncrementCount">Click me</button>

@functions {
    private readonly ClassA _a = new ClassA();
    private readonly ClassB _b = new ClassB(_a);

    class ClassA
    {
        public int CurrentCount { get; set; }
    }

    class ClassB
    {
        private readonly ClassA _classA;

        public ClassB(ClassA classA)
        {
            _classA = classA;
        }

        public void IncrementCount() => _classA.CurrentCount++;
    }
}

我收到此错误：

错误CS0236字段初始值设定项无法引用非静态字段，方法或属性'__Counter._a'

该线程解释了如何在标准类中解决此错误：

Why can't you use 'this' in member initializers?

但为此，它需要一个构造函数。

是否可以在Blazor组件中添加构造函数？

如何解决这个错误？

Answer 1

为了保持课程只读，你应该转移到"code-behind"。然后你可以在构造函数上实例化类：

@page "/counter"
@inherits CounterBase
<h1>Counter</h1>

<p>Current count: @_a.CurrentCount ...

CounterBase.cs

using Microsoft.AspNetCore.Blazor.Components;

namespace YourApp.Pages
{

    public class ClassA
    {
        public int CurrentCount { get; set; }
    }

    public class ClassB
    {
        private readonly ClassA _classA;

        public ClassB(ClassA classA)
        {
            _classA = classA;
        }

        public void IncrementCount() => _classA.CurrentCount++;
    }

    public class CounterBase : BlazorComponent
    {
        protected readonly ClassA _a;
        protected readonly ClassB _b;

        //constructor
        public CounterBase()
        {
            _a = new ClassA();
            _b = new ClassB(_a);
        }
        ...