How to stop webview2 from opening new browser window rather than inside the browser

To stop the link from opening in a new window, you subscribe to the CoreWebView2_NewWindowRequested as you have found out.

To do that, the easiest way is to subscribe to the CoreWebView2InitializationCompleted first.

In properties window for the WebView2 control, double click CoreWebView2InitializationCompleted - that will auto generate the eventhandler:

Now you add the CoreWebView2_NewWindowRequested eventhandler and set e.NewWindow to the current CoreWebView2.

Here's the code (assuming your WebView2 control is called webView21):

private void WebView21_CoreWebView2InitializationCompleted(object sender, Microsoft.Web.WebView2.Core.CoreWebView2InitializationCompletedEventArgs e)
{
    webView21.CoreWebView2.NewWindowRequested += CoreWebView2_NewWindowRequested;
}

private void CoreWebView2_NewWindowRequested(object sender, Microsoft.Web.WebView2.Core.CoreWebView2NewWindowRequestedEventArgs e)
{
    e.NewWindow = webView21.CoreWebView2;
}

Now the link opens in the same window (your WebView2 control).

To complement @Poul Bak answer I was having this exact problem in VB.Net but all the answers were for C# so im going to post it in here if anyone else needs it.

First make sure to import this:

Imports Microsoft.Web.WebView2.Core
Imports Microsoft.Web.WebView2.WinForms

And then add this 2 events just replace wVBrowser with your Webview2 control name.

Private Sub wVBrowser_CoreWebView2InitializationCompleted(sender As Object, e As CoreWebView2InitializationCompletedEventArgs) Handles wVBrowser.CoreWebView2InitializationCompleted
            AddHandler wVBrowser.CoreWebView2.NewWindowRequested, AddressOf CoreWebView2_NewWindowRequested
        End Sub
Private Sub CoreWebView2_NewWindowRequested(ByVal sender As Object, ByVal e As Microsoft.Web.WebView2.Core.CoreWebView2NewWindowRequestedEventArgs)
            e.Handled = True
        End Sub

I tried like Poul Bak mentioned above it worked for me, may be your event subscription place might be wrong, try like below.

Subscribe for NewWindowRequested event after CoreWebView2 initialized.

For Ex:

 public Form1()
    {
        InitializeComponent();

        //https://docs.microsoft.com/en-us/microsoft-edge/webview2/get-started/winforms
        InitializeAsync();
     
    }

    async void InitializeAsync()
    {
        await webView.EnsureCoreWebView2Async(null);
        webView.CoreWebView2.NewWindowRequested += CoreWebView2_NewWindowRequested;
    }

private void CoreWebView2_NewWindowRequested(object sender, CoreWebView2NewWindowRequestedEventArgs e)
    {
        e.NewWindow = webView.CoreWebView2;
    }

Happy Coding ... !!!!