vb.netコード
Dim request = webView2.CoreWebView2.Environment.CreateWebResourceRequest( uri:="https://hoge.com/hoge.html", Method:="POST", postData:=New System.IO.MemoryStream(System.Text.Encoding.UTF8.GetBytes("test1=data1&test2=data2")), Headers:="Content-Type: application/x-www-form-urlencoded " & vbCrLf) webView2.CoreWebView2.NavigateWithWebResourceRequest(request)