WebClient Class

.NET Framework (current version)

Note
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Provides common methods for sending data to and receiving data from a resource identified by a URI.

Namespace: System.Net
Assembly: System (in System.dll)

Inheritance Hierarchy

System.Object
System.MarshalByRefObject
System.ComponentModel.Component
System.Net.WebClient

Syntax

C++

[ComVisibleAttribute(true)]
public class WebClient : Component

Constructors

	Name	Description
	WebClient()	Initializes a new instance of the WebClient class.

Properties

	Name	Description
	AllowReadStreamBuffering	Obsolete. Gets or sets a value that indicates whether to buffer the data read from the Internet resource for a WebClient instance.
	AllowWriteStreamBuffering	Obsolete. Gets or sets a value that indicates whether to buffer the data written to the Internet resource for a WebClient instance.
	BaseAddress	Gets or sets the base URI for requests made by a WebClient.
	CachePolicy	Gets or sets the application's cache policy for any resources obtained by this WebClient instance using WebRequest objects.
	CanRaiseEvents	Gets a value indicating whether the component can raise an event.(Inherited from Component.)
	Container	Gets the IContainer that contains the Component.(Inherited from Component.)
	Credentials	Gets or sets the network credentials that are sent to the host and used to authenticate the request.
	DesignMode	Gets a value that indicates whether the Component is currently in design mode.(Inherited from Component.)
	Encoding	Gets and sets the Encoding used to upload and download strings.
	Events	Gets the list of event handlers that are attached to this Component.(Inherited from Component.)
	Headers	Gets or sets a collection of header name/value pairs associated with the request.
	IsBusy	Gets whether a Web request is in progress.
	Proxy	Gets or sets the proxy used by this WebClient object.
	QueryString	Gets or sets a collection of query name/value pairs associated with the request.
	ResponseHeaders	Gets a collection of header name/value pairs associated with the response.
	Site	Gets or sets the ISite of the Component.(Inherited from Component.)
	UseDefaultCredentials	Gets or sets a Boolean value that controls whether the DefaultCredentials are sent with requests.

Methods

	Name	Description
	CancelAsync()	Cancels a pending asynchronous operation.
	CreateObjRef(Type)	Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object.(Inherited from MarshalByRefObject.)
	Dispose()	Releases all resources used by the Component.(Inherited from Component.)
	Dispose(Boolean)	Releases the unmanaged resources used by the Component and optionally releases the managed resources.(Inherited from Component.)
	DownloadData(String)	Downloads the resource as a Byte array from the URI specified.
	DownloadData(Uri)	Downloads the resource as a Byte array from the URI specified.
	DownloadDataAsync(Uri)	Downloads the resource as a Byte array from the URI specified as an asynchronous operation.
	DownloadDataAsync(Uri, Object)	Downloads the resource as a Byte array from the URI specified as an asynchronous operation.
	DownloadDataTaskAsync(String)	Downloads the resource as a Byte array from the URI specified as an asynchronous operation using a task object.
	DownloadDataTaskAsync(Uri)	Downloads the resource as a Byte array from the URI specified as an asynchronous operation using a task object.
	DownloadFile(String, String)	Downloads the resource with the specified URI to a local file.
	DownloadFile(Uri, String)	Downloads the resource with the specified URI to a local file.
	DownloadFileAsync(Uri, String)	Downloads, to a local file, the resource with the specified URI. This method does not block the calling thread.
	DownloadFileAsync(Uri, String, Object)	Downloads, to a local file, the resource with the specified URI. This method does not block the calling thread.
	DownloadFileTaskAsync(String, String)	Downloads the specified resource to a local file as an asynchronous operation using a task object.
	DownloadFileTaskAsync(Uri, String)	Downloads the specified resource to a local file as an asynchronous operation using a task object.
	DownloadString(String)	Downloads the requested resource as a String. The resource to download is specified as a String containing the URI.
	DownloadString(Uri)	Downloads the requested resource as a String. The resource to download is specified as a Uri.
	DownloadStringAsync(Uri)	Downloads the resource specified as a Uri. This method does not block the calling thread.
	DownloadStringAsync(Uri, Object)	Downloads the specified string to the specified resource. This method does not block the calling thread.
	DownloadStringTaskAsync(String)	Downloads the resource as a String from the URI specified as an asynchronous operation using a task object.
	DownloadStringTaskAsync(Uri)	Downloads the resource as a String from the URI specified as an asynchronous operation using a task object.
	Equals(Object)	Determines whether the specified object is equal to the current object.(Inherited from Object.)
	Finalize()	Releases unmanaged resources and performs other cleanup operations before the Component is reclaimed by garbage collection.(Inherited from Component.)
	GetHashCode()	Serves as the default hash function. (Inherited from Object.)
	GetLifetimeService()	Retrieves the current lifetime service object that controls the lifetime policy for this instance.(Inherited from MarshalByRefObject.)
	GetService(Type)	Returns an object that represents a service provided by the Component or by its Container.(Inherited from Component.)
	GetType()	Gets the Type of the current instance.(Inherited from Object.)
	GetWebRequest(Uri)	Returns a WebRequest object for the specified resource.
	GetWebResponse(WebRequest)	Returns the WebResponse for the specified WebRequest.
	GetWebResponse(WebRequest, IAsyncResult)	Returns the WebResponse for the specified WebRequest using the specified IAsyncResult.
	InitializeLifetimeService()	Obtains a lifetime service object to control the lifetime policy for this instance.(Inherited from MarshalByRefObject.)
	MemberwiseClone()	Creates a shallow copy of the current Object.(Inherited from Object.)
	MemberwiseClone(Boolean)	Creates a shallow copy of the current MarshalByRefObject object.(Inherited from MarshalByRefObject.)
	OnDownloadDataCompleted(DownloadDataCompletedEventArgs)	Raises the DownloadDataCompleted event.
	OnDownloadFileCompleted(AsyncCompletedEventArgs)	Raises the DownloadFileCompleted event.
	OnDownloadProgressChanged(DownloadProgressChangedEventArgs)	Raises the DownloadProgressChanged event.
	OnDownloadStringCompleted(DownloadStringCompletedEventArgs)	Raises the DownloadStringCompleted event.
	OnOpenReadCompleted(OpenReadCompletedEventArgs)	Raises the OpenReadCompleted event.
	OnOpenWriteCompleted(OpenWriteCompletedEventArgs)	Raises the OpenWriteCompleted event.
	OnUploadDataCompleted(UploadDataCompletedEventArgs)	Raises the UploadDataCompleted event.
	OnUploadFileCompleted(UploadFileCompletedEventArgs)	Raises the UploadFileCompleted event.
	OnUploadProgressChanged(UploadProgressChangedEventArgs)	Raises the UploadProgressChanged event.
	OnUploadStringCompleted(UploadStringCompletedEventArgs)	Raises the UploadStringCompleted event.
	OnUploadValuesCompleted(UploadValuesCompletedEventArgs)	Raises the UploadValuesCompleted event.
	OnWriteStreamClosed(WriteStreamClosedEventArgs)	Obsolete. Raises the WriteStreamClosed event.
	OpenRead(String)	Opens a readable stream for the data downloaded from a resource with the URI specified as a String.
	OpenRead(Uri)	Opens a readable stream for the data downloaded from a resource with the URI specified as a Uri
	OpenReadAsync(Uri)	Opens a readable stream containing the specified resource. This method does not block the calling thread.
	OpenReadAsync(Uri, Object)	Opens a readable stream containing the specified resource. This method does not block the calling thread.
	OpenReadTaskAsync(String)	Opens a readable stream containing the specified resource as an asynchronous operation using a task object.
	OpenReadTaskAsync(Uri)	Opens a readable stream containing the specified resource as an asynchronous operation using a task object.
	OpenWrite(String)	Opens a stream for writing data to the specified resource.
	OpenWrite(String, String)	Opens a stream for writing data to the specified resource, using the specified method.
	OpenWrite(Uri)	Opens a stream for writing data to the specified resource.
	OpenWrite(Uri, String)	Opens a stream for writing data to the specified resource, by using the specified method.
	OpenWriteAsync(Uri)	Opens a stream for writing data to the specified resource. This method does not block the calling thread.
	OpenWriteAsync(Uri, String)	Opens a stream for writing data to the specified resource. This method does not block the calling thread.
	OpenWriteAsync(Uri, String, Object)	Opens a stream for writing data to the specified resource, using the specified method. This method does not block the calling thread.
	OpenWriteTaskAsync(String)	Opens a stream for writing data to the specified resource as an asynchronous operation using a task object.
	OpenWriteTaskAsync(String, String)	Opens a stream for writing data to the specified resource as an asynchronous operation using a task object.
	OpenWriteTaskAsync(Uri)	Opens a stream for writing data to the specified resource as an asynchronous operation using a task object.
	OpenWriteTaskAsync(Uri, String)	Opens a stream for writing data to the specified resource as an asynchronous operation using a task object.
	ToString()	Returns a String containing the name of the Component, if any. This method should not be overridden.(Inherited from Component.)
	UploadData(String, Byte[])	Uploads a data buffer to a resource identified by a URI.
	UploadData(String, String, Byte[])	Uploads a data buffer to the specified resource, using the specified method.
	UploadData(Uri, Byte[])	Uploads a data buffer to a resource identified by a URI.
	UploadData(Uri, String, Byte[])	Uploads a data buffer to the specified resource, using the specified method.
	UploadDataAsync(Uri, Byte[])	Uploads a data buffer to a resource identified by a URI, using the POST method. This method does not block the calling thread.
	UploadDataAsync(Uri, String, Byte[])	Uploads a data buffer to a resource identified by a URI, using the specified method. This method does not block the calling thread.
	UploadDataAsync(Uri, String, Byte[], Object)	Uploads a data buffer to a resource identified by a URI, using the specified method and identifying token.
	UploadDataTaskAsync(String, Byte[])	Uploads a data buffer that contains a Byte array to the URI specified as an asynchronous operation using a task object.
	UploadDataTaskAsync(String, String, Byte[])	Uploads a data buffer that contains a Byte array to the URI specified as an asynchronous operation using a task object.
	UploadDataTaskAsync(Uri, Byte[])	Uploads a data buffer that contains a Byte array to the URI specified as an asynchronous operation using a task object.
	UploadDataTaskAsync(Uri, String, Byte[])	Uploads a data buffer that contains a Byte array to the URI specified as an asynchronous operation using a task object.
	UploadFile(String, String)	Uploads the specified local file to a resource with the specified URI.
	UploadFile(String, String, String)	Uploads the specified local file to the specified resource, using the specified method.
	UploadFile(Uri, String)	Uploads the specified local file to a resource with the specified URI.
	UploadFile(Uri, String, String)	Uploads the specified local file to the specified resource, using the specified method.
	UploadFileAsync(Uri, String)	Uploads the specified local file to the specified resource, using the POST method. This method does not block the calling thread.
	UploadFileAsync(Uri, String, String)	Uploads the specified local file to the specified resource, using the POST method. This method does not block the calling thread.
	UploadFileAsync(Uri, String, String, Object)	Uploads the specified local file to the specified resource, using the POST method. This method does not block the calling thread.
	UploadFileTaskAsync(String, String)	Uploads the specified local file to a resource as an asynchronous operation using a task object.
	UploadFileTaskAsync(String, String, String)	Uploads the specified local file to a resource as an asynchronous operation using a task object.
	UploadFileTaskAsync(Uri, String)	Uploads the specified local file to a resource as an asynchronous operation using a task object.
	UploadFileTaskAsync(Uri, String, String)	Uploads the specified local file to a resource as an asynchronous operation using a task object.
	UploadString(String, String)	Uploads the specified string to the specified resource, using the POST method.
	UploadString(String, String, String)	Uploads the specified string to the specified resource, using the specified method.
	UploadString(Uri, String)	Uploads the specified string to the specified resource, using the POST method.
	UploadString(Uri, String, String)	Uploads the specified string to the specified resource, using the specified method.
	UploadStringAsync(Uri, String)	Uploads the specified string to the specified resource. This method does not block the calling thread.
	UploadStringAsync(Uri, String, String)	Uploads the specified string to the specified resource. This method does not block the calling thread.
	UploadStringAsync(Uri, String, String, Object)	Uploads the specified string to the specified resource. This method does not block the calling thread.
	UploadStringTaskAsync(String, String)	Uploads the specified string to the specified resource as an asynchronous operation using a task object.
	UploadStringTaskAsync(String, String, String)	Uploads the specified string to the specified resource as an asynchronous operation using a task object.
	UploadStringTaskAsync(Uri, String)	Uploads the specified string to the specified resource as an asynchronous operation using a task object.
	UploadStringTaskAsync(Uri, String, String)	Uploads the specified string to the specified resource as an asynchronous operation using a task object.
	UploadValues(String, NameValueCollection)	Uploads the specified name/value collection to the resource identified by the specified URI.
	UploadValues(String, String, NameValueCollection)	Uploads the specified name/value collection to the resource identified by the specified URI, using the specified method.
	UploadValues(Uri, NameValueCollection)	Uploads the specified name/value collection to the resource identified by the specified URI.
	UploadValues(Uri, String, NameValueCollection)	Uploads the specified name/value collection to the resource identified by the specified URI, using the specified method.
	UploadValuesAsync(Uri, NameValueCollection)	Uploads the data in the specified name/value collection to the resource identified by the specified URI. This method does not block the calling thread.
	UploadValuesAsync(Uri, String, NameValueCollection)	Uploads the data in the specified name/value collection to the resource identified by the specified URI, using the specified method. This method does not block the calling thread.
	UploadValuesAsync(Uri, String, NameValueCollection, Object)	Uploads the data in the specified name/value collection to the resource identified by the specified URI, using the specified method. This method does not block the calling thread, and allows the caller to pass an object to the method that is invoked when the operation completes.
	UploadValuesTaskAsync(String, NameValueCollection)	Uploads the specified name/value collection to the resource identified by the specified URI as an asynchronous operation using a task object.
	UploadValuesTaskAsync(String, String, NameValueCollection)	Uploads the specified name/value collection to the resource identified by the specified URI as an asynchronous operation using a task object.
	UploadValuesTaskAsync(Uri, NameValueCollection)	Uploads the specified name/value collection to the resource identified by the specified URI as an asynchronous operation using a task object.
	UploadValuesTaskAsync(Uri, String, NameValueCollection)	Uploads the specified name/value collection to the resource identified by the specified URI as an asynchronous operation using a task object.

Events

	Name	Description
	Disposed	Occurs when the component is disposed by a call to the Dispose method. (Inherited from Component.)
	DownloadDataCompleted	Occurs when an asynchronous data download operation completes.
	DownloadFileCompleted	Occurs when an asynchronous file download operation completes.
	DownloadProgressChanged	Occurs when an asynchronous download operation successfully transfers some or all of the data.
	DownloadStringCompleted	Occurs when an asynchronous resource-download operation completes.
	OpenReadCompleted	Occurs when an asynchronous operation to open a stream containing a resource completes.
	OpenWriteCompleted	Occurs when an asynchronous operation to open a stream to write data to a resource completes.
	UploadDataCompleted	Occurs when an asynchronous data-upload operation completes.
	UploadFileCompleted	Occurs when an asynchronous file-upload operation completes.
	UploadProgressChanged	Occurs when an asynchronous upload operation successfully transfers some or all of the data.
	UploadStringCompleted	Occurs when an asynchronous string-upload operation completes.
	UploadValuesCompleted	Occurs when an asynchronous upload of a name/value collection completes.
	WriteStreamClosed	Obsolete. Occurs when an asynchronous operation to write data to a resource using a write stream is closed.

Remarks

The WebClient class provides common methods for sending data to or receiving data from any local, intranet, or Internet resource identified by a URI.

The WebClient class uses the WebRequest class to provide access to resources. WebClient instances can access data with any WebRequest descendant registered with the WebRequest.RegisterPrefix method.

Note
By default, the .NET Framework supports URIs that begin with http:, https:, ftp:, and file: scheme identifiers.

The following table describes WebClient methods for uploading data to a resource.

Method	Description
OpenWrite	Retrieves a Stream used to send data to the resource.
OpenWriteAsync	Retrieves a Stream used to send data to the resource, without blocking the calling thread.
UploadData	Sends a byte array to the resource and returns a Byte array containing any response.
UploadDataAsync	Sends a Byte array to the resource, without blocking the calling thread.
UploadFile	Sends a local file to the resource and returns a Byte array containing any response.
UploadFileAsync	Sends a local file to the resource, without blocking the calling thread.
UploadValues	Sends a NameValueCollection to the resource and returns a Byte array containing any response.
UploadValuesAsync	Sends a NameValueCollection to the resource and returns a Byte array containing any response, without blocking the calling thread.
UploadString	Sends a String to the resource, without blocking the calling thread.
UploadStringAsync	Sends a String to the resource, without blocking the calling thread.

The following table describes WebClient methods for downloading data from a resource.

Method	Description
OpenRead	Returns the data from a resource as a Stream.
OpenReadAsync	Returns the data from a resource, without blocking the calling thread.
DownloadData	Downloads data from a resource and returns a Byte array.
DownloadDataAsync	Downloads data from a resource and returns a Byte array, without blocking the calling thread.
DownloadFile	Downloads data from a resource to a local file.
DownloadFileAsync	Downloads data from a resource to a local file, without blocking the calling thread.
DownloadString	Downloads a String from a resource and returns a String.
DownloadStringAsync	Downloads a String from a resource, without blocking the calling thread.

You can use the CancelAsync method to cancel asynchronous operations that have not completed.

A WebClient instance does not send optional HTTP headers by default. If your request requires an optional header, you must add the header to the Headers collection. For example, to retain queries in the response, you must add a user-agent header. Also, servers may return 500 (Internal Server Error) if the user agent header is missing.

AllowAutoRedirect is set to true in WebClient instances.

Notes to Inheritors:

Derived classes should call the base class implementation of WebClient to ensure the derived class works as expected.

Examples

The following code example takes the URI of a resource, retrieves it, and displays the response.

C++

using System;
using System.Net;
using System.IO;

public class Test
{
    public static void Main (string[] args)
    {
        if (args == null || args.Length == 0)
        {
            throw new ApplicationException ("Specify the URI of the resource to retrieve.");
        }
        WebClient client = new WebClient ();

        // Add a user agent header in case the 
        // requested URI contains a query.

        client.Headers.Add ("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)");

        Stream data = client.OpenRead (args[0]);
        StreamReader reader = new StreamReader (data);
        string s = reader.ReadToEnd ();
        Console.WriteLine (s);
        data.Close ();
        reader.Close ();
    }
}