使用RestSharp上传文件：有时不工作

Question

我尝试将文件上传到C＃Winform中的本地REST服务器。点击按钮时，几次都没有发生任何事情。但是在点击几下按钮后，文件就会上传。我想知道为什么它有时会起作用，为什么它有时不起作用。我之前在VS 2010上开发了它，然后我搬到了VS 2017.

private void btnUpload_Click(object sender, EventArgs e)
{
    try
    {
        var client = new RestClient(baseUrl + "/upload_file");
        var request = new RestRequest();
        request.Method = Method.POST;
        request.RequestFormat = DataFormat.Json;
        request.AddHeader("Authorization", "Bearer " + loginUser.Token);
        request.AddHeader("Content-Type", "multipart/form-data");
        request.AddFile("userphoto", 
            filePath, MimeTypeHelper.GetMimeType(filePath));
        request.AddParameter("username", loginUser.Username);

        IRestResponse response = client.Execute(request);
        if (response.StatusCode == HttpStatusCode.Created)
        {
            Console.WriteLine(response.Content);
            MessageBox.Show("The file uploaded!");
        }
    }
    catch (WebException ex)
    {
        Console.WriteLine(ex.Message);
        Console.WriteLine("Not updated photo!");
    }
}