I’m trying to build a REST Client usign Async CTP. I’m new to the CTP and hence, afetr going through a number of examples on the internet, I got a clas built for just posting (GET or POST). Here is the class so far:
using System;
using System.Collections.Specialized;
using System.IO;
using System.Net;
using System.Text;
using System.Threading.Tasks;
using System.Web;
namespace RESTClient.Core {
/// <summary>
/// Submits post data to a url.
/// </summary>
public class PostSubmitter {
#region Backing Store
private string m_url = string.Empty;
private NameValueCollection m_values = new NameValueCollection();
private PostTypeEnum m_type = PostTypeEnum.Get;
#endregion
#region Constructors
/// <summary>
/// Default constructor.
/// </summary>
public PostSubmitter() {
}
/// <summary>
/// Constructor that accepts a url as a parameter
/// </summary>
/// <param name="url">The url where the post will be submitted to.</param>
public PostSubmitter(string url)
: this() {
m_url = url;
}
/// <summary>
/// Constructor allowing the setting of the url and items to post.
/// </summary>
/// <param name="url">the url for the post.</param>
/// <param name="values">The values for the post.</param>
public PostSubmitter(string url, NameValueCollection values)
: this(url) {
m_values = values;
}
#endregion
#region Properties
/// <summary>
/// Gets or sets the url to submit the post to.
/// </summary>
public string Url {
get {
return m_url;
}
set {
m_url = value;
}
}
/// <summary>
/// Gets or sets the name value collection of items to post.
/// </summary>
public NameValueCollection PostItems {
get {
return m_values;
}
set {
m_values = value;
}
}
/// <summary>
/// Gets or sets the type of action to perform against the url.
/// </summary>
public PostTypeEnum Type {
get {
return m_type;
}
set {
m_type = value;
}
}
#endregion
/// <summary>
/// Posts the supplied data to specified url.
/// </summary>
/// <returns>a string containing the result of the post.</returns>
public async Task<String> Post() {
StringBuilder parameters = new StringBuilder();
for (int i = 0; i < m_values.Count; i++) {
EncodeAndAddItem(ref parameters, m_values.GetKey(i), m_values[i]);
}
string result = await PostData(m_url, parameters.ToString());
return result;
}
/// <summary>
/// Posts the supplied data to specified url.
/// </summary>
/// <param name="url">The url to post to.</param>
/// <returns>a string containing the result of the post.</returns>
public async Task<String> Post(string url) {
m_url = url;
return await this.Post();
}
/// <summary>
/// Posts the supplied data to specified url.
/// </summary>
/// <param name="url">The url to post to.</param>
/// <param name="values">The values to post.</param>
/// <returns>a string containing the result of the post.</returns>
public async Task<String> Post(string url, NameValueCollection values) {
m_values = values;
return await this.Post(url);
}
/// <summary>
/// Posts data to a specified url. Note that this assumes that you have already url encoded the post data.
/// </summary>
/// <param name="postData">The data to post.</param>
/// <param name="url">the url to post to.</param>
/// <returns>Returns the result of the post.</returns>
private async Task<String> PostData(string url, string postData) {
HttpWebRequest request = null;
if (m_type == PostTypeEnum.Post) {
Uri uri = new Uri(url);
request = (HttpWebRequest)WebRequest.Create(uri);
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
request.ContentLength = postData.Length;
using (Stream writeStream = await request.GetRequestStreamAsync()) {
UTF8Encoding encoding = new UTF8Encoding();
byte[] bytes = encoding.GetBytes(postData);
writeStream.Write(bytes, 0, bytes.Length);
}
}
else {
Uri uri = new Uri(url + "?" + postData);
request = (HttpWebRequest)WebRequest.Create(uri);
request.Method = "GET";
}
string result = string.Empty;
using (HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync()) {
using (Stream responseStream = response.GetResponseStream()) {
using (StreamReader readStream = new StreamReader(responseStream, Encoding.UTF8)) {
result = readStream.ReadToEnd();
}
}
}
return result;
}
/// <summary>
/// Encodes an item and ads it to the string.
/// </summary>
/// <param name="baseRequest">The previously encoded data.</param>
/// <param name="dataItem">The data to encode.</param>
/// <returns>A string containing the old data and the previously encoded data.</returns>
private void EncodeAndAddItem(ref StringBuilder baseRequest, string key, string dataItem) {
if (baseRequest == null) {
baseRequest = new StringBuilder();
}
if (baseRequest.Length != 0) {
baseRequest.Append("&");
}
baseRequest.Append(key);
baseRequest.Append("=");
baseRequest.Append(HttpUtility.UrlEncode(dataItem));
}
}
}
And this is how I’m using it:
private void ButtonSubmit_Click(object sender, EventArgs e) {
ButtonReset.Enabled = false;
TextResponse.Text = String.Empty;
TextResponse.Text += "Begining..." + Environment.NewLine;
try {
TextResponse.Text += Task.Factory.StartNew(() => PostSomeData().Wait());
//TextResponse.Text += PostSomeData();
TextResponse.Text += Environment.NewLine;
TextResponse.Text += "Function Done!" + Environment.NewLine;
}
catch (Exception ex) {
TextResponse.Text += "Exception!" + Environment.NewLine + "Message: " + ex.Message + Environment.NewLine;
}
finally {
ButtonReset.Enabled = true;
TextResponse.Text += "Function Ended!";
}
}
private async Task<String> PostSomeData() {
PostSubmitter post = new PostSubmitter();
post.Url = TextURL.Text.Trim();
post.PostItems.Add(TextParam01.Text.Trim(), TextValue01.Text.Trim());
post.PostItems.Add(TextParam02.Text.Trim(), TextValue02.Text.Trim());
post.PostItems.Add(TextParam03.Text.Trim(), TextValue03.Text.Trim());
post.PostItems.Add(TextParam04.Text.Trim(), TextValue04.Text.Trim());
post.PostItems.Add(TextParam05.Text.Trim(), TextValue05.Text.Trim());
post.PostItems.Add(TextParam06.Text.Trim(), TextValue06.Text.Trim());
post.PostItems.Add(TextParam07.Text.Trim(), TextValue07.Text.Trim());
post.PostItems.Add(TextParam08.Text.Trim(), TextValue08.Text.Trim());
post.PostItems.Add(TextParam09.Text.Trim(), TextValue09.Text.Trim());
post.PostItems.Add(TextParam10.Text.Trim(), TextValue10.Text.Trim());
post.PostItems.Add(TextParam11.Text.Trim(), TextValue11.Text.Trim());
post.PostItems.Add(TextParam12.Text.Trim(), TextValue12.Text.Trim());
post.Type = PostTypeEnum.Post;
return await post.Post();
}
The behaviour is not quite as expected. The line TextResponse.Text += Task.Factory.StartNew(() => PostSomeData().Wait()); whiz-by and I get no exceptions and here is the resulting string:
Begining…
System.Threading.Tasks.Task
Function Done!
Function Ended!
Now, if I’m using a POST, I get an exception after the above. Digging into the exception reveals a 500 Internal Server Error
However, if i’m using GET, nothing happens. No exception and just the same final result.
Am I doing something wrong in the PostSubmitter Class?
Here is the UI shot with the paramaeters:
Regards.
Update #1
I have modified the click event on the UI as well. However
- It only works if the PostType is GET. POST is not working.
- The UI hangs while the operation lasts
The modifications:
private async void ButtonSubmit_Click(object sender, EventArgs e) {
ButtonReset.Enabled = false;
TextResponse.Text = String.Empty;
TextResponse.Text += "Begining..." + Environment.NewLine;
try {
TextResponse.Text += await PostSomeData();
TextResponse.Text += Environment.NewLine;
TextResponse.Text += "Function Done!" + Environment.NewLine;
}
catch (Exception ex) {
TextResponse.Text += "Exception!" + Environment.NewLine + "Message: " + ex.Message + Environment.NewLine;
}
finally {
ButtonReset.Enabled = true;
TextResponse.Text += "Function Ended!";
}
}
Your code is only partially asynchronous; take a good look at
PostData.In particular,
ReadToEndneeds to be asynchronous:This is in addition to making your event handler asynchronous, as others have mentioned.