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Requests a synchronous or asynchronous file download from a specific URL. Assigns method, destination URL, and other optional attributes of a pending request.

Syntax

 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.

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 / Method Defined In HTTP (RFC-2616) Defined In WebDAV (RFC-2518) Function
GET HTTP WebDAV Request URI
POST HTTP WebDAV Send data to server
HEAD HTTP WebDAV Request URI without body
PUT HTTP WebDAV Store data for URI
DELETE HTTP WebDAV Delete data for URI
MOVE WebDAV Move URI to to new location
PROPFIND WebDAV Request URI Properties
PROPPATCH WebDAV Update or Delete URI Properties
MKCOL WebDAV Create collection at URI
COPY WebDAV Create copy of URI
LOCK WebDAV Create Lock
UNLOCK WebDAV Remove Lock
OPTIONS HTTP WebDAV Request 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