Asp.Net IPN侦听器（成功但DB未更新）

Question

这是我的IPN监听器，我的所有购买都是成功的，但是当涉及到更新数据库时，没有任何反应。我甚至没有尝试使用帖子中的任何数据，只是一个简单的测试＆＃39;插入

    [HttpPost]
public async Task<ActionResult> Ipn()
{

    var ipn = Request.Form.AllKeys.ToDictionary(k => k, k => Request[k]);
    ipn.Add("cmd", "_notify-validate");

    var isIpnValid = await ValidateIpnAsync(ipn);
    if (isIpnValid)
    {
        con.Open();
        SqlCommand cmd = new SqlCommand("INSERT INTO paypal(transaction_id) VALUES('Test')", con);
        cmd.ExecuteNonQuery();
        con.Close();
    }

    return new EmptyResult();
}

private static async Task<bool> ValidateIpnAsync(IEnumerable<KeyValuePair<string, string>> ipn)
{
    using (var client = new HttpClient())
    {


        const string PayPalUrl = "https://www.paypal.com/cgi-bin/webscr";

        // This is necessary in order for PayPal to not resend the IPN.
        await client.PostAsync(PayPalUrl, new StringContent(string.Empty));

        var response = await client.PostAsync(PayPalUrl, new FormUrlEncodedContent(ipn));

        var responseString = await response.Content.ReadAsStringAsync();
        return (responseString == "VERIFIED");
    }
}