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open method

Assigns method, destination URL, and other optional attributes of a pending request.

Syntax


HRESULT retVal = object.open(bstrMethod, bstrUrl, varAsync, varUser, varPassword);

Parameters

bstrMethod [in]

Type: BSTR

BSTR that specifies the HTTP method used to open the connection: such as GET, POST, or HEAD. This parameter is not case-sensitive.

bstrUrl [in]

Type: BSTR

BSTR that specifies either the absolute or a relative URL of the XML data or server-side Web services.

varAsync [in, optional]

Type: VARIANT

VARIANT that specifies VARIANT_TRUE for asynchronous operation (the call returns immediately), or VARIANT_FALSE for synchronous operation. If VARIANT_TRUE, assign a callback handler to the onreadystatechange property to determine when the call has completed. If not specified, the default is VARIANT_TRUE.

Performance Note:   When varAsync is set to VARIANT_FALSE, IHTMLXMLHttpRequest::send operations are synchronous. When a IHTMLXMLHttpRequest::send operation is in progress, other operations are suspended. This affects user input, display updates, and similar tasks. As a result, this setting should not be used when users expect to interact with an app while a IHTMLXMLHttpRequest::send operation is active.

varUser [in, optional]

Type: VARIANT

VARIANT that specifies the name of the user for authentication. If this parameter is NULL ("") or missing and the site requires authentication, the component displays a logon window.

varPassword [in, optional]

Type: VARIANT

VARIANT that specifies the password for authentication. This parameter is ignored if the user parameter is NULL ("") or missing.

Return value

Type: HRESULT

If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Standards information

Remarks

IHTMLXMLHttpRequest::open was introduced in Windows Internet Explorer 7.

The following HTTP verbs and World Wide Web Distributed Authoring and Versioning (WebDAV) methods are supported:

Verb / MethodDefined In HTTP (RFC-2616)Defined In WebDAV (RFC-2518)Function
GETHTTPWebDAVRequest URI
POSTHTTPWebDAVSend data to server
HEADHTTPWebDAVRequest URI without body
PUTHTTPWebDAVStore data for URI
DELETEHTTPWebDAVDelete data for URI
MOVEWebDAVMove URI to to new location
PROPFINDWebDAVRequest URI Properties
PROPPATCHWebDAVUpdate or Delete URI Properties
MKCOLWebDAVCreate collection at URI
COPYWebDAVCreate copy of URI
LOCKWebDAVCreate Lock
UNLOCKWebDAVRemove Lock
OPTIONSHTTPWebDAVRequest URI Options

 

Windows Internet Explorer caches the results of HTTP GET requests in the Temporary Internet Files (TIF) folder. In most cases, caching improves performance for data that will not change frequently. To guarantee that the results are not cached, use POST.

Security Warning:   Cross-domain, cross-port, and mixed protocol requests are not allowed. The bstrUrl parameter may only specify files in the same domain, using the same port and protocol method, as that from which the page is served.

Although this method accepts credentials passed via parameter, those credentials are not automatically sent to the server on the first request. The varUser and varPassword parameters are not transmitted unless the server challenges the client for credentials with a 401 - Access Denied response.

After calling this method, use IHTMLXMLHttpRequest::send to send the request and data, if any, to the server.

See also

Reference
IHTMLXMLHttpRequest::abort
onreadystatechange
Other Resources
Communicating XML Data over the Web with WebDAV

 

 

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