What difference is there between the WebClient and the HttpWebRequest classes in .NET? They both do very similar things. In fact, why weren't they merged into one class (too many methods/variables etc may be one reason but there are other classes in .NET which breaks that rule).
Thanks.
WebClient is a higher-level abstraction built on top of HttpWebRequest to simplify the most common tasks. For instance, if you want to get the content out of an HttpWebResponse, you have to read from the response stream:
var http = (HttpWebRequest)WebRequest.Create("http://example.com");
var response = http.GetResponse();
var stream = response.GetResponseStream();
var sr = new StreamReader(stream);
var content = sr.ReadToEnd();
With WebClient, you just do DownloadString:
var client = new WebClient();
var content = client.DownloadString("http://example.com");
Note: I left out the using statements from both examples for brevity. You should definitely take care to dispose your web request objects properly.
In general, WebClient is good for quick and dirty simple requests and HttpWebRequest is good for when you need more control over the entire request.
Also WebClient doesn't have timeout property. And that's the problem, because dafault value is 100 seconds and that's too much to indicate if there's no Internet connection.
Workaround for that problem is here https://stackoverflow.com/a/3052637/1303422
I know its too longtime to reply but just as an information purpose for future readers:
WebRequest
System.Object
System.MarshalByRefObject
System.Net.WebRequest
The WebRequest is an abstract base class. So you actually don't use it directly. You use it through it derived classes - HttpWebRequest and FileWebRequest.
You use Create method of WebRequest to create an instance of WebRequest. GetResponseStream returns data stream.
There are also FileWebRequest and FtpWebRequest classes that inherit from WebRequest. Normally, you would use WebRequest to, well, make a request and convert the return to either HttpWebRequest, FileWebRequest or FtpWebRequest, depend on your request. Below is an example:
Example:
var _request = (HttpWebRequest)WebRequest.Create("http://stackoverflow.com");
var _response = (HttpWebResponse)_request.GetResponse();
WebClient
System.Object
System.MarshalByRefObject
System.ComponentModel.Component
System.Net.WebClient
WebClient provides common operations to sending and receiving data from a resource identified by a URI. Simply, it’s a higher-level abstraction of HttpWebRequest. This ‘common operations’ is what differentiate WebClient from HttpWebRequest, as also shown in the sample below:
Example:
var _client = new WebClient();
var _stackContent = _client.DownloadString("http://stackoverflow.com");
There are also DownloadData and DownloadFile operations under WebClient instance. These common operations also simplify code of what we would normally do with HttpWebRequest. Using HttpWebRequest, we have to get the response of our request, instantiate StreamReader to read the response and finally, convert the result to whatever type we expect. With WebClient, we just simply call DownloadData, DownloadFile or DownloadString.
However, keep in mind that WebClient.DownloadString doesn’t consider the encoding of the resource you requesting. So, you would probably end up receiving weird characters if you don’t specify an encoding.
NOTE: Basically "WebClient takes few lines of code as compared to WebRequest"
Related
I'm working on a C# console application which calls external REST APIs with RestSharp.
The issue now is that I have to access an API that only allows a custom request method like FOOBAR instead of the traditional GET or POST.
using RestSharp;
var request = new RestRequest();
request.Method = Method.POST;
Unfortunately, I haven't seen anything pertaining to custom request methods in RestSharp's docs or GitHub issues section.
Keep in mind that I only have a basic knowledge on this, so my trials might be considered silly.
I've tried assigning a string to it but it only accepts an enum.
request.Method = "FOOBAR"; // Does not accept strings
I've also tried converting a string to enum using code from this answer, but this defaults to a GET. It might be like that due to my converted string not being in their enum Method.
Enum.TryParse("FOOBAR", out Method customRequestMethod);
request.Method = customRequestMethod; // Defaults to GET
If this is not possible with RestSharp, is this feature doable with HttpClient or Flurl?
I would like to connect automatically from a client to a server with an IP address in C# and get a text file from the server.
What would be the best way to achieve this ?
WebClient
The simplest way to do so is using "WebClient". See https://msdn.microsoft.com/en-us/library/system.net.webclient(v=vs.110).aspx
This class has a function called
public string DownloadString(string address)
You can use this to download the text file to memory.
For more Methods (e.g. DownloadFile) visit the given link. Note: This Method might hang the window if executed in the UI-Thread while downloading the content. Either use a second Thread to do the stuff or use the asynchronous methods if possible.
In this case you would rather use this:
public Task<string> DownloadStringTaskAsync(string address)
More Information about Async: https://msdn.microsoft.com/en-us/library/dd537609(v=vs.110).aspx
It is easy to achieve using a WebRequest as follows.
// Create a request for the URL.
WebRequest request = WebRequest.Create("http://yourdomain.com/textfile");
// Get the response.
WebResponse response = request.GetResponse();
// Get the stream containing content returned by the server.
Stream dataStream = response.GetResponseStream();
// Open the stream using a StreamReader for easy access.
StreamReader reader = new StreamReader(dataStream);
// Read the content.
string responseFromServer = reader.ReadToEnd();
I'm writing this short module where I have to modify an addressed resource with a PUT method. I'm using the WebRequest class to make this URI request and the GetRequestStream() to get the stream to write to.
However, it seems that after a couple of successful method calls (and using the PUT to modify resources) via this method below, my application hangs and then throws a WebException: The request timed out. error. Here's what the code looks like:
public void SendOffMessageToResource(int res_ID){
var httpWebRequest = WebRequest.Create ("http://192.168.x.x/api/sample_user/resources/1/state");
httpWebRequest.ContentType = "application/json";
httpWebRequest.Method = "PUT";
using (var streamWriter = new StreamWriter(httpWebRequest.GetRequestStream())) //here's where the VS seems to take a long long time to step over to the next line when the error happens.
{
string json = "{\"on\":false}";
streamWriter.Write(json);
streamWriter.Close();
}
}
I am already disposing the StreamWriter. I'm not even using the GetResponse() method, because all I need to do on this URI is actually modify the addressed resource with PUT method. I am not sure why it still throws an error and hangs the application. The search of previous threads only revealed that people should be using using statements to dispose resources, but I'm already doing that I think or perhaps I'm missing something? Do I always need to use GetResponse() to complete the request and dispose that always in addition to this?
Do I always need to use GetResponse() to complete the request and dispose that always in addition to this?
Yes, just that.
I am using WebClient to retrieve a website. I decided to set If-Modified-Since because if the website hasn't changed, I don't want to get it again:
var c = new WebClient();
c.Headers[HttpRequestHeader.IfModifiedSince] = Last_refreshed.ToUniversalTime().ToString("r");
Where Last_refreshed is a variable in which I store the time I've last seen the website.
But when I run this, I get a WebException with the text:
The 'If-Modified-Since' header must be modified using the appropriate property or method.
Parameter name: name
Turns out the API docs mention this:
In addition, some other headers are also restricted when using a WebClient object. These restricted headers include, but are not limited to the following:
Accept
Connection
Content-Length
Expect (when the value is set to "100-continue")
If-Modified-Since
Range
Transfer-Encoding
The HttpWebRequest class has properties for setting some of the above headers. If it is important for an application to set these headers, then the HttpWebRequest class should be used instead of the WebRequest class.
So does this mean there's no way to set them from WebClient? Why not? What's wrong with specifying If-Modified-Since in a normal HTTP GET?
I know I can just use HttpWebRequest, but I don't want to because it's too much work (have to do a bunch of casting, can't just get the content as a string).
Also, I know Cannot set some HTTP headers when using System.Net.WebRequest is related, but it doesn't actually answer my question.
As unwieldy as it may be, I have opted to subclass WebClient in order to add the functionality in a way that mimics the way WebClient typically works (in which headers are consumed by / reset after each use):
public class ApiWebClient : WebClient {
public DateTime? IfModifiedSince { get; set; }
protected override WebRequest GetWebRequest(Uri address) {
var webRequest = base.GetWebRequest(address);
var httpWebRequest = webRequest as HttpWebRequest;
if (httpWebRequest != null) {
if (IfModifiedSince != null) {
httpWebRequest.IfModifiedSince = IfModifiedSince.Value;
IfModifiedSince = null;
}
// Handle other headers or properties here
}
return webRequest;
}
}
This has the advantage of not having to write boilerplate for the standard operations that WebClient provides, while still offering some of the flexibility of using WebRequest.
I am new to C#, I need to send HTTP GET request and read answer. I am familiar with Java and easy can do it URLConnection class but I don't know in c#. Can anybody help ?
The simplest way is to use WebClient:
WebClient client = new WebClient();
string text = client.DownloadString(url);
(That's the synchronous form; it also supports asynchronous requests.)
For more control you might want to use HttpWebRequest.