你需要注意 IHttpAsyncHandler 而不是 IHttpHandler 并将其注册在web.config文件中。浏览器还将观察连接限制，因此请确保IIS配置正确以处理多个连接，保持活动等。

以下详细介绍： http://msdn.microsoft.com/en-us/library/ms227433.aspx

I have a form in my website which posts json to the async handler which validates the data and return back the resonse OK or error and i will make the redirect on the client based on the response give by my handler.

But when the response is ok, i want to perform some tasks asynchronously. But the asynchronous calls are not working inside the .ashx code. it is always synchronous.

Could you please give me an advice on this.?

code:

public class ValidateHandler : IHttpHandler, IRequiresSessionState
    {

        public void ProcessRequest(HttpContext context)
        {
            NameValueCollection nvcForm = context.Request.Form;
            Dictionary<string, string> errorFieldsDict = new Dictionary<string, string>();


            foreach (string nameValueKey in nvcForm.AllKeys)
            {
                regExpToTest = string.Empty;
                switch (nameValueKey)
                {
                    case "firstName":
                      //validate
                        break;
                    case "lastName":
                       //validate
                        break;
                    case "email":
                        //validate
                        break;
                    case "phoneNumber":
                    //validate
                        break;
                    case "phoneCountryCode":
                        //validate
                        break;
                    case "country":
                     //validate
                        break;
                    case "addressLine1":
                        //validate
                        break;
                    case "addressLine2":
                       //validate
                        break;
                    case "city":
                        //validate
                        break;
                    case "postalCode":
                        //validate
                        break;
                    default:
                        //validate
                        break;
                }
                if (!string.IsNullOrEmpty(regExpToTest) && !Regex.IsMatch(nvcForm[nameValueKey], regExpToTest) && !string.IsNullOrEmpty(nvcForm[nameValueKey]))
                {
                    errorFieldsDict.Add(nameValueKey, "Please Enter Correct Value");
                    isSuccess = false;
                }
            }

            //Do your business logic here and finally

            if (isSuccess)
            {
                JavaScriptSerializer serializer = new JavaScriptSerializer();
                try
                {
                    Dictionary<string, object> formValues = GetDictionaryForJson(nvcForm);
                    string previoiusUrl = GetRequestedURL(context);
                    string partner = string.Empty;
                    if (System.Web.HttpContext.Current.Session["yourpartner"] != null)
                        partner = System.Web.HttpContext.Current.Session["yourpartner"].ToString();
                    else if (System.Web.HttpContext.Current.Request.QueryString["utm_source"] != null)
                        partner = System.Web.HttpContext.Current.Request.QueryString["utm_source"];
                    else
                        partner = "company";
                    formValues.Add("partnerCode", partner);
                    string brochureType = string.Empty;
                    if (!string.IsNullOrEmpty(nvcForm["addressLine1"]) || !string.IsNullOrEmpty(nvcForm["addressLine2"]))
                        brochureType = "FBRO";
                    else
                        brochureType = "EBRO";
                    //Create a row in database
                    Item programItem = Sitecore.Context.Database.Items.GetItem(programRootpath + nvcForm["selectYourProgram"]); ;
                    AsyncMailSender caller = new AsyncMailSender(SendEmail);
                    IAsyncResult result = caller.BeginInvoke(programItem, nvcForm["email"], null, null);
                }
                catch (Exception ex)
                {
                    isSuccess = false;
                    Log.Error("Enquiry handler failure: " + ex.Message, ex);
                    response.response = "error";
                    response.message = ex.Message;
                    context.Response.ContentType = "application/json";
                    context.Response.Write(JsonConvert.SerializeObject(response));
                }
                if (isSuccess)
                {
                    response.response = "ok";
                    context.Response.ContentType = "application/json";
                    context.Response.Write(JsonConvert.SerializeObject(response));
                }

            }
            else
            {
                response.response = "errorFields";
                response.errorFields = errorFieldsDict;
                context.Response.ContentType = "application/json";
                string responseJson = JsonConvert.SerializeObject(response);
                context.Response.Write(JsonConvert.SerializeObject(response, Newtonsoft.Json.Formatting.None));
            }

        }
        private string GetRequestedURL(HttpContext context)
        {
            string previousURL = string.Empty;
            try
            {
                previousURL = context.Request.ServerVariables["HTTP_REFERER"];
            }
            catch
            {
                previousURL = context.Request.Url.AbsolutePath;
            }
            return previousURL;
        }
        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
        private void SendEmail(Item programItem, string toEmail)
        {

            if (programItem != null)
            {
               SendEmail()

            }
        }
        private Dictionary<string, object> GetDictionaryForJson(NameValueCollection formValues)
        {
            Dictionary<string, object> formDictionary = new Dictionary<string, object>();
            foreach (string key in formValues.AllKeys)
            {
                formDictionary.Add(key, formValues[key]);
            }

            return formDictionary;
        }

    }
    public delegate void AsyncMailSender(Item program, string toAddress);

PS: I did hide some code which is just our business.But Would be great if you can comment on that.

thanks guys

You need to implmement IHttpAsyncHandler rather than IHttpHandler and register it as such in the web.config file. Browsers will also observe connection limits, so make sure IIS is configured properly to handle multiple connections, keep-alive, etc.

Here's a detailed walk through: http://msdn.microsoft.com/en-us/library/ms227433.aspx