Http Client Http Client Http Client Http Client Class
Definition
Sends HTTP requests and receives HTTP responses from a resource identified by a URI.
In This Article
The following sample code shows how to GET content from a Web server as a string.
The HttpClient class is often used by an app to download and then parse text. It is possible that the character encoding specified in the Content-Type header by an HTTP server does not match the character encoding of the HTTP response body (the XML encoding in an XML document, for example). One way to use HttpClient with text is to call the GetStringAsync method and pass the returned string to the text parser. However, this can result in errors if the Content-Type is not a type expressible as a string. A reliable way to use HttpClient with an XML parser is to call the GetBufferAsync method and parse the buffer for the "" element. Then use the character encoding specified ("
The HttpClient class instance acts as a session to send HTTP requests and receive responses. An HttpClient instance is a collection of settings that apply to all requests executed by that instance. In addition, every HttpClient instance uses its own connection pool, isolating its requests from requests executed by other HttpClient instances.
The HttpClient also acts as a class to use with filters for more specific HTTP clients. An example would be an HttpClientFilter that provides additional methods specific to a social network service (a GetFriends method, for instance).
If an app using HttpClient and related classes in the Windows.Web.Http namespace downloads large amounts of data (50 megabytes or more), then the app should stream those downloads and not use the default buffering. If the default buffering is used the client memory usage will get very large, potentially resulting in reduced performance.
For sample code in C#/VB/C++ and XAML that shows how to use HttpClient to connect to an HTTP server, see HttpClient.
For sample code in JavaScript and HTML that shows how to use HttpClient to connect to an HTTP server, see Connecting to an HTTP server using Windows.Web.Http.
Constructors
HttpClient() HttpClient() HttpClient() HttpClient()
Initializes a new instance of the HttpClient class.
HttpClient(IHttpFilter) HttpClient(IHttpFilter) HttpClient(IHttpFilter) HttpClient(IHttpFilter)
Initializes a new instance of the HttpClient class with a specific filter for handling HTTP response messages.
The HTTP filter to use for handling response messages.
The sample code shows creating an HttpClient to use a custom filter.
If a null reference (Nothing in Visual Basic) is specified for the filter parameter, the default transport handler for receiving responses with no filter is used.
Close() Close() Close() Close()
Closes the HttpClient instance and releases allocated resources.
The Close method releases allocated resources used by the HttpClient instance. The Close method can manage the lifetime of system resources (the underlying socket and memory for the HttpClient, for example) used by a Windows Runtime object.
In the .NET Framework 4.5, this method projects as the Dispose method. In Visual C++ component extensions (C++/CX), this method projects as the destructor (delete operator).
Apps written in JavaScript, C#, or VB.NET use garbage collection to release resources. So the HttpClient object and associated resources doesn't get released until the garbage collection pass runs. The Close method allows an app to release these resources early rather than waiting for the object to be released by garbage collection.
Apps written in C++ or CX don't have a Close method since these apps can destroy the object. In C++ and CX, objects are released when they fall out of program scope or as part of the destructor (delete operator) for the object.
DeleteAsync(Uri) DeleteAsync(Uri) DeleteAsync(Uri) DeleteAsync(Uri)
Send a DELETE request to the specified Uri as an asynchronous operation.
The Uri the request is sent to.
The object representing the asynchronous operation.
This operation will not block. The returned IAsyncOperationWithProgress(HttpResponseMessage, HttpProgress) object will complete after the whole response (including content) is read.
Exception Handling
You must write code to handle exceptions when you call this method. Exceptions can result from parameter validation errors, name resolutions failures, and network errors. Exceptions from network errors (loss of connectivity, connection failures, and HTTP server failures, for example) can happen at any time. These errors result in exceptions being thrown. If not handled by your app, an exception can cause your entire app to be terminated by the runtime. For more information on how to handle exceptions, see Handling exceptions in network apps.
Below are the exceptions that this function throws.
E_INVALIDARG
The uri parameter was null reference (Nothing in Visual Basic).
Dispose() Dispose() Dispose() Dispose()
Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
GetAsync(Uri) GetAsync(Uri) GetAsync(Uri) GetAsync(Uri)
Send a GET request to the specified Uri as an asynchronous operation.
The Uri to which the request is to be sent.
The object representing the asynchronous operation.
This operation will not block. The returned IAsyncOperationWithProgress(HttpResponseMessage, HttpProgress) object will complete after the whole response (including content) is read.
For sample code in C#/VB/C++ and XAML that shows how to use HttpClient and GetAsync(Uri) to connect to an HTTP server and send a GET request, see HttpClient.
For sample code in JavaScript and HTML that shows how to use HttpClient and GetAsync(Uri) to connect to an HTTP server and send a GET request, see Connecting to an HTTP server using Windows.Web.Http.
Below are the exceptions that this function throws.
COMException
Thrown when a feature-specific HRESULT is returned from a method call.
This is the most common exception that is thrown by networking methods. An app should use the HRESULT from the exception to determine the cause of the error.
AccessDeniedException
Thrown when access is denied to a resource or feature. This exception occurs when an app doesn't have the required network capabilities set in the app manifest for the network operation requested.
InvalidArgumentException
Thrown when one of the arguments that are provided to a method is not valid.
If user-supplied input caused this exception, an app could inform the user and request new input.
ObjectDisposedException
Thrown when an operation is performed on a disposed object.
OutOfMemoryException
Thrown when insufficient memory is available to complete the operation.
GetAsync(Uri, HttpCompletionOption) GetAsync(Uri, HttpCompletionOption) GetAsync(Uri, HttpCompletionOption) GetAsync(Uri, HttpCompletionOption)
Send a GET request to the specified Uri with an HTTP completion option as an asynchronous operation.
The Uri the request is sent to.
An HTTP completion option value that indicates when the operation should be considered completed.
The object representing the asynchronous operation.
This operation will not block. The returned IAsyncOperationWithProgress(HttpResponseMessage, HttpProgress) object will complete based on the completionOption parameter after part or all of the response (including content) is read.
Below are the exceptions that this content throws.
COMException
Thrown when a feature-specific HRESULT is returned from a method call.
This is the most common exception that is thrown by networking methods. An app should use the HRESULT from the exception to determine the cause of the error.
AccessDeniedException
Thrown when access is denied to a resource or feature. This exception occurs when an app doesn't have the required network capabilities set in the app manifest for the network operation requested.
InvalidArgumentException
Thrown when one of the arguments that are provided to a method is not valid.
If user-supplied input caused this exception, an app could inform the user and request new input.
ObjectDisposedException
Thrown when an operation is performed on a disposed object.
OutOfMemoryException
Thrown when insufficient memory is available to complete the operation.
GetBufferAsync(Uri) GetBufferAsync(Uri) GetBufferAsync(Uri) GetBufferAsync(Uri)
Send a GET request to the specified Uri and return the response body as a buffer in an asynchronous operation.
The Uri the request is sent to.
The object representing the asynchronous operation.
This operation will not block. The returned IAsyncOperationWithProgress(IBuffer, HttpProgress) object will complete after the whole response body is read.
The HttpClient class is often used by an app to download and then parse text. It is possible that the character encoding specified in the Content-Type header by an HTTP server does not match the character encoding of the HTTP response body (the XML encoding in an XML document, for example). One way to use HttpClient with text is to call the GetStringAsync method and pass the returned string to the text parser. However, this can result in errors if the Content-Type is not a type expressible as a string. A reliable way to use HttpClient with an XML parser is to call the GetBufferAsync method and parse the buffer for the "" element. Then use the character encoding specified ("
Below are the exceptions that this function throws.
E_INVALIDARG
The uri parameter was a null reference (Nothing in Visual Basic).
GetInputStreamAsync(Uri) GetInputStreamAsync(Uri) GetInputStreamAsync(Uri) GetInputStreamAsync(Uri)
Send a GET request to the specified Uri and return the response body as a stream in an asynchronous operation.
The Uri the request is sent to.
The object representing the asynchronous operation.
This operation will not block. The returned IAsyncOperationWithProgress(IInputStream, HttpProgress) object will complete after the whole response body is read. This method does not buffer the stream, so this method can support long streams of arbitrary length.
Below are the exceptions that this function throws.
E_INVALIDARG
The uri parameter was a null reference (Nothing in Visual Basic).
GetStringAsync(Uri) GetStringAsync(Uri) GetStringAsync(Uri) GetStringAsync(Uri)
Send a GET request to the specified Uri and return the response body as a string in an asynchronous operation.
The Uri the request is sent to.
The object representing the asynchronous operation.
This operation will not block. The returned IAsyncOperationWithProgress(String, HttpProgress) object will complete after the whole response body is read.
The HttpClient class is often used by an app to download and then parse text. It is possible that the character encoding specified in the Content-Type header by an HTTP server does not match the character encoding of the HTTP response body (the XML encoding in an XML document, for example). One way to use HttpClient with text is to call the GetStringAsync method and pass the returned string to the text parser. However, this can result in errors if the Content-Type is not a type expressible as a string. A reliable way to use HttpClient with an XML parser is to call the GetBufferAsync method and parse the buffer for the "" element. Then use the character encoding specified ("
Below are the exceptions that this function throws.
E_INVALIDARG
The uri parameter was a null reference (Nothing in Visual Basic).
Exception Handling
You must write code to handle exceptions when you call this method. Exceptions can result from parameter validation errors, name resolutions failures, and network errors. Exceptions from network errors (loss of connectivity, connection failures, and HTTP server failures, for example) can happen at any time. These errors result in exceptions being thrown. If not handled by your app, an exception can cause your entire app to be terminated by the runtime. For more information on how to handle exceptions, see Handling exceptions in network apps.
PostAsync(Uri, IHttpContent) PostAsync(Uri, IHttpContent) PostAsync(Uri, IHttpContent) PostAsync(Uri, IHttpContent)
Send a POST request to the specified Uri as an asynchronous operation.
The Uri the request is sent to.
The HTTP request content to send to the server.
The object representing the asynchronous operation.
This operation will not block. The returned IAsyncOperationWithProgress(HttpResponseMessage, HttpProgress) object will complete after the whole response (including content) is read.
The PostAsync and PutAsync methods only allow setting a limited number of HTTP content headers. In contrast, the SendRequestAsync method allows setting headers on the request message as well as on the HTTP content to be sent.
Below are the exceptions that this function throws.
E_INVALIDARG
The uri parameter was a null reference (Nothing in Visual Basic).
Exception Handling
You must write code to handle exceptions when you call this method. Exceptions can result from parameter validation errors, name resolutions failures, and network errors. Exceptions from network errors (loss of connectivity, connection failures, and HTTP server failures, for example) can happen at any time. These errors result in exceptions being thrown. If not handled by your app, an exception can cause your entire app to be terminated by the runtime. For more information on how to handle exceptions, see Handling exceptions in network apps.
PutAsync(Uri, IHttpContent) PutAsync(Uri, IHttpContent) PutAsync(Uri, IHttpContent) PutAsync(Uri, IHttpContent)
Send a PUT request to the specified Uri as an asynchronous operation.
The Uri the request is sent to.
The HTTP request content to send to the server.
The object representing the asynchronous operation.
This operation will not block. The returned IAsyncOperationWithProgress(HttpResponseMessage, HttpProgress) object will complete after the whole response (including content) is read.
The PutAsync and PostAsync methods only allow setting a limited number of HTTP content headers. In contrast, the SendRequestAsync method allows setting headers on the request message as well as on the HTTP content to be sent.
Below are the exceptions that this function throws.
E_INVALIDARG
The uri parameter was a null reference (Nothing in Visual Basic).
SendRequestAsync(HttpRequestMessage) SendRequestAsync(HttpRequestMessage) SendRequestAsync(HttpRequestMessage) SendRequestAsync(HttpRequestMessage)
Send an HTTP request as an asynchronous operation.
The HTTP request message to send.
The object representing the asynchronous operation.
This operation will not block. The returned IAsyncOperationWithProgress(HttpResponseMessage, HttpProgress) object will complete after the whole response (including content) is read.
The HttpRequestMessage passed in the request parameter allows the SendRequestAsync method to set headers on the request message as well as on the HTTP content to be sent. In contrast, the PostAsync and PutAsync methods only allow setting a more limited set of HTTP content headers.
Below are the exceptions that this function throws.
E_INVALIDARG
The request parameter was a null reference (Nothing in Visual Basic).
E_ILLEGAL_METHOD_CALL
The request message was already sent by the HttpClient instance.
SendRequestAsync(HttpRequestMessage, HttpCompletionOption) SendRequestAsync(HttpRequestMessage, HttpCompletionOption) SendRequestAsync(HttpRequestMessage, HttpCompletionOption) SendRequestAsync(HttpRequestMessage, HttpCompletionOption)
Send an HTTP request with an HTTP completion option as an asynchronous operation.
The HTTP request message to send.
A value that indicates whether the HttpClient operation is considered completed when all of the response is read, or when just the headers are read.
The object representing the asynchronous operation.
This operation will not block. The returned IAsyncOperationWithProgress(HttpResponseMessage, HttpProgress) object will complete depending on the value of the completionOption parameter.
The HttpRequestMessage passed in the request parameter allows the SendRequestAsync method to set headers on the request message as well as on the HTTP content to be sent. In contrast, the PostAsync and PutAsync methods only allow setting a more limited set of HTTP content headers.
Below are the exceptions that this function throws.
E_INVALIDARG
The request parameter was a null reference (Nothing in Visual Basic).
E_ILLEGAL_METHOD_CALL
The request message was already sent by the HttpClient instance.
Exception Handling
You must write code to handle exceptions when you call this method. Exceptions can result from parameter validation errors, name resolutions failures, and network errors. Exceptions from network errors (loss of connectivity, connection failures, and HTTP server failures, for example) can happen at any time. These errors result in exceptions being thrown. If not handled by your app, an exception can cause your entire app to be terminated by the runtime. For more information on how to handle exceptions, see Handling exceptions in network apps.
ToString() ToString() ToString() ToString()
Returns a string that represents the current HttpClient object.
A string that represents the current object.
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