即使在 CoreWebView2InitializationCompleted 事件之后，EnsureCoreWebView2Async 也没有准备好

Question

根据 Microsoft 在 Windows 窗体中使用 webView2 的入门（截至 2021 年 3 月 9 日），我有以下代码（未设置 webView2.source；从 Form.Designer.cs 中编辑）：

    public Form1() {
      InitializeComponent();
      InitializeAsync();
    }

    async void InitializeAsync() {
      Console.WriteLine("InitializeAsync starting");
      await webView2.EnsureCoreWebView2Async(null);
      Console.WriteLine("InitializeAsync done");
    }

    private void Form1_Load(object sender, EventArgs e) {
      Console.WriteLine("Load event");
    }

    private void webView2_CoreWebView2InitializationCompleted(object sender, CoreWebView2InitializationCompletedEventArgs e) {
      Console.WriteLine("CoreWebView2InitializationCompleted event");
      if ((webView2 == null) || (webView2.CoreWebView2 == null))
        Console.WriteLine("not ready");
      webView2.NavigateToString(File.ReadAllText("index.html"));
    }

我很惊讶在 NavigateToString() 处遇到异常：

System.InvalidOperationException
  HResult=0x80131509
  Message=The instance of CoreWebView2 is uninitialized and unable to complete this operation. See InitializeAsync.
  Source=Microsoft.Web.WebView2.WinForms
  StackTrace:
   at Microsoft.Web.WebView2.WinForms.WebView2.VerifyInitializedGuard()
   at Microsoft.Web.WebView2.WinForms.WebView2.NavigateToString(String htmlContent)
   at webview2_base.Form1.webView2_CoreWebView2InitializationCompleted(Object sender, CoreWebView2InitializationCompletedEventArgs e) in E:\Visual Studio 2019\source\repos\explore\webview2_base\Form1.cs:line 37
   at Microsoft.Web.WebView2.WinForms.WebView2.<InitCoreWebView2Async>d__13.MoveNext()

控制台输出为：

InitializeAsync starting
Load event
CoreWebView2InitializationCompleted event
Exception thrown: 'System.InvalidOperationException' in Microsoft.Web.WebView2.WinForms.dll
An exception of type 'System.InvalidOperationException' occurred in Microsoft.Web.WebView2.WinForms.dll but was not handled in user code
The instance of CoreWebView2 is uninitialized and unable to complete this operation. See InitializeAsync.

那是怎么回事？考虑到事件的标签，我会认为 CoreWebView2 已经完成了它的初始化。

如果在 InitializeAsync 中的“等待”之后将 Navigate 移至该代码，则该代码有效。我可能不明白“等待”，我认为它会延迟 Form 构造函数和 Load 事件的完成，直到 CoreWebView2 完成之后。

我想将 Navigate 放在 Form Load 事件处理程序中（但它会在 CoreWebView2 准备好之前触发）。

我是不是不明白，或者这里是否存在与 CoreWebView2 相关的错误，即使它在“initializeComplete”事件触发后也没有被初始化？

VS2019 16.9、Net 4.7.2、webview2 版本 91.0.823.0 金丝雀

更新 (2021-03-19)：如果将 'webView2.NavigateToString()' 替换为 'webView2.CoreWebView2.NavigateToString()'，它就可以工作。但鉴于事件名称，它似乎应该在那个时候工作。

Answer 1

您需要使用await InitializeAsync();，这意味着async void InitializeAsync 应该是async Task InitializeAsync。由于 async 不能与构造函数一起使用，因此您必须从 Form1_Load 调用 InitializeAsync。

尝试以下方法：

using System.Diagnostics;

选项 1：

public Form1()
{
    InitializeComponent();
}

private async void Form1_Load(object sender, EventArgs e)
{
    webView2.CoreWebView2InitializationCompleted += WebView_CoreWebView2InitializationCompleted;

    Debug.WriteLine("before InitializeAsync");
    await InitializeAsync();
    Debug.WriteLine("after InitializeAsync");

    //webView2.CoreWebView2.Navigate("https://www.microsoft.com");
    //Debug.WriteLine("after Navigate");

    if ((webView2 == null) || (webView2.CoreWebView2 == null))
    {
        Debug.WriteLine("not ready");
    }

    webView2.NavigateToString(System.IO.File.ReadAllText("index.html"));

    Debug.WriteLine("after NavigateToString");
}

private async Task InitializeAsync()
{
    Debug.WriteLine("InitializeAsync");
    await webView2.EnsureCoreWebView2Async(null);
    Debug.WriteLine("WebView2 Runtime version: " + webView2.CoreWebView2.Environment.BrowserVersionString);
}


private void WebView_CoreWebView2InitializationCompleted(object sender, Microsoft.Web.WebView2.Core.CoreWebView2InitializationCompletedEventArgs e)
{
    Debug.WriteLine("WebView_CoreWebView2InitializationCompleted");
}

输出：

before InitializeAsync
InitializeAsync
WebView_CoreWebView2InitializationCompleted
WebView2 Runtime version: 89.0.774.48
after InitializeAsync
after NavigateToString

更新 - 这是另一个选项

选项 2：

public Form1()
{
    InitializeComponent();
}

private async void Form1_Load(object sender, EventArgs e)
{
    webView2.CoreWebView2InitializationCompleted += WebView_CoreWebView2InitializationCompleted;

    Debug.WriteLine("before InitializeAsync");
    await InitializeAsync();
    Debug.WriteLine("after InitializeAsync");

}

private async Task InitializeAsync()
{
    Debug.WriteLine("InitializeAsync");
    await webView2.EnsureCoreWebView2Async(null);
    Debug.WriteLine("WebView2 Runtime version: " + webView2.CoreWebView2.Environment.BrowserVersionString);

    //webView2.CoreWebView2.Navigate("https://www.microsoft.com");
    //Debug.WriteLine("after Navigate");

    if ((webView2 == null) || (webView2.CoreWebView2 == null))
    {
        Debug.WriteLine("not ready");
    }

    webView2.NavigateToString(System.IO.File.ReadAllText("index.html"));

    Debug.WriteLine("after NavigateToString");
}


private void WebView_CoreWebView2InitializationCompleted(object sender, Microsoft.Web.WebView2.Core.CoreWebView2InitializationCompletedEventArgs e)
{
    Debug.WriteLine("WebView_CoreWebView2InitializationCompleted");
}

输出：

before InitializeAsync
InitializeAsync
WebView_CoreWebView2InitializationCompleted
WebView2 Runtime version: 89.0.774.48
after NavigateToString
after InitializeAsync