将子组件中的事件改为async方法，并在方法内部调用StateHasChanged()方法。

示例代码：

子组件：

public partial class ChildComponent: ComponentBase
{
    [Parameter]
    public int ChildValue { get; set; }
    
    [Parameter]
    public EventCallback ChildValueChanged { get; set; }
    
    private async Task OnChange()
    {
        ChildValue++;
        await ChildValueChanged.InvokeAsync(ChildValue);
        StateHasChanged();
    }
}

父组件：

public partial class ParentComponent: ComponentBase
{
    private int parentValue = 0;
    
    private void HandleChildValueChanged(int newValue)
    {
        parentValue = newValue;
        StateHasChanged();
    }
    
    protected override void OnInitialized()
    {
        base.OnInitialized();
        StateHasChanged();
    }
    
    
}