Blazor Webassembly 可以通过JavaScript Interop与JavaScript通信。想要检测浏览器窗口状态的变化，可以使用JavaScript来获取窗口的visibility状态，再将值传递给Blazor。下面是一个示例：

JavaScript代码：

//get the window visibility status
function getWindowStatus() {
    return document.visibilityState;
}

//listen for changes to the window visibility status
document.addEventListener('visibilitychange', function () {
    //call C# method through JavaScript Interop
    DotNet.invokeMethodAsync('BlazorApp', 'OnWindowVisibilityChanged', getWindowStatus());
});

在Blazor代码中，需要在调用JavaScript之前定义好对应的JavaScript函数：

@inject IJSRuntime JSRuntime

@code {
    protected override async Task OnInitializedAsync()
    {
        //register JavaScript function with Blazor
        await JSRuntime.InvokeVoidAsync("registerWindowStatus", DotNetObjectReference.Create(this));
    }

    //called by JavaScript function through JavaScript Interop
    [JSInvokable]
    public async Task OnWindowVisibilityChanged(string status)
    {
        //do something with window visibility status
    }
}