SWbemServices.ExecMethodAsync method

Artikkeli
04/27/2021

The ExecMethodAsync method of the SWbemServices object executes a method that is exported by a method provider. The call immediately returns to the client while the inbound parameters are forwarded to the appropriate provider where the method executes. Information and status are returned to the caller through events delivered to the sink that is specified in objWbemSink. The provider, rather than Windows Management Instrumentation (WMI), implements the method.

The method is called in the asynchronous mode. For more information, see Calling a Method.

For more information and an explanation of this syntax, see Document Conventions for the Scripting API.

Syntax

SWbemServices.ExecMethodAsync( _
  ByVal objWbemSink, _
  ByVal strObjectPath, _
  ByVal strMethodName, _
  [ ByVal objWbemInParams ], _
  [ ByVal iFlags ], _
  [ ByVal objWbemNamedValueSet ], _
  [ ByVal objWbemAsyncContext ] _
)

Parameters

objWbemSink: Required. Create an SWbemSink object to receive the objects. Object sink that receives the result of the method call. The outbound parameters are sent to the SWbemSink.OnObjectReady event of the supplied object sink. The results of the call mechanism are sent to the SWbemSink.OnCompleted event of the supplied object sink. Be aware that SWbemSink.OnCompleted does not receive the return code of the WMI method. However, it receives the return code of the actual call-return mechanism, and is only useful for verifying that the call occurred or that it failed for mechanical reasons. The result code that is returned from the WMI method is returned in the outbound parameter object supplied to SWbemSink.OnObjectReady. If any error code is returned, then the supplied IWbemObjectSink object is not used. If the call is successful, then the user's IWbemObjectSink implementation is called to indicate the result of the operation.
strObjectPath: Required. A string that contains the object path of the object for which the method is executed. For more information, see Describing the Location of a WMI Object.
strMethodName: Required. The name of the method to execute.
objWbemInParams [optional]: An SWbemObject object that contains the input parameters for the method that is executed. By default, this parameter is undefined. For more information, see Constructing InParameters Objects and Parsing OutParameters Objects.
iFlags [optional]: Integer that determines the behavior of the call. This parameter can accept the following values.
wbemFlagSendStatus (128 (0x80)): Causes asynchronous calls to send status updates to the OnProgress event handler for the object sink.
wbemFlagDontSendStatus (0 (0x0)): Prevents asynchronous calls from sending status updates to the OnProgress event handler for the object sink.

objWbemNamedValueSet [optional]

Typically, this is undefined. Otherwise, this is an SWbemNamedValueSet object whose elements represent the context information that can be used by the provider that is servicing the request. A provider that supports or requires such information must document the recognized value names, data type of the value, allowed values, and semantics.

objWbemAsyncContext [optional]

A SWbemNamedValueSet object that returns to the object sink to identify the source of the original asynchronous call. Use this parameter if you are making multiple asynchronous calls using the same object sink. To use this parameter, create an SWbemNamedValueSet object and use the SWbemNamedValueSet.Add method to add a value that identifies the asynchronous call you are making. This SWbemNamedValueSet object is returned to the object sink and the source of the call can be extracted using the SWbemNamedValueSet.Item method. For more information, see Making an Asynchronous Call with VBScript.

Return value

This method does not return a value. If the call is successful, an OutParameters object, which is also an SWbemObject is supplied to the sink that is specified in objWbemSink. The returned OutParameters object contains the output parameters and return value for the method being executed. For more information, see Constructing InParameters Objects and Parsing OutParameters Objects.

Error codes

After the completion of the ExecMethodAsync method, the Err object may contain one of the error codes listed in the following list.

wbemErrFailed - 2147749889 (0x80041001): Unspecified error.
wbemErrInvalidClass - 2147749904 (0x80041010): Specified class was not valid.
wbemErrInvalidParameter - 2147749896 (0x80041008): A specified parameter is not valid.
wbemErrOutOfMemory - 2147749894 (0x80041006): Not enough memory to complete the operation.
wbemErrInvalidMethod - 2147749934 (0x8004102E): Requested method was not available.
wbemErrAccessDenied - 2147749891 (0x80041003): Current user was not authorized to execute the method.

Remarks

If the method executed has input parameters, the InParameters object in the objWbemInParam parameter must be the same as the description in the Constructing InParameters Objects and Parsing OutParameters Objects topics.

Use SWbemServices.ExecMethodAsync as an alternative to direct access for executing a provider method when it is not possible to execute a method directly. For example, use it with a scripting language that does not support output parameters, that is, if your method has OUT parameters. Otherwise, it is recommended that you use direct access to invoke a method. For more information, see Manipulating Class and Instance Information.

The SWbemServices.ExecMethodAsync method requires an object path. If the script already contains an SWbemObject object, you can call SWbemObject.ExecMethodAsync.

This call returns immediately. The status information is returned to the caller through call-backs delivered to the sink that is specified in objWbemSink. To continue processing when the call is completed, implement a subroutine for the objWbemSink.OnCompleted event.

An asynchronous callback allows a non-authenticated user to provide data to the sink. This poses security risks to your scripts and applications. For more information about how to eliminate the risks, see Setting Security on an Asynchronous Call.

Use the objWbemAsyncContext parameter to verify the source of a call.

Examples

The following code example shows the ExecMethodAsync method. The script creates a Win32_Process object that represents a process that is running Notepad. It shows the setting up of an InParameters object and how to obtain results from an OutParameters object. For a script that shows the same operations performed synchronously, see SWbemServices.ExecMethod. For an example of using direct access, see Create Method in Class Win32_Process. For an example of the same operation using SWbemObject, see SWbemObject.ExecMethodAsync.

' Connect to WMI.
set Services = getobject("winmgmts:root\cimv2")

' Obtain the class definition object
' of a Win32_Process object.
Set oProcess = Services.Get("Win32_Process")

' Create the SWbemMethod.InParameters object
' to hold the input parameter required
' for the Win32_Process.Create method call.
' The oProcess.Methods_("Create") call
' obtains a class object that defines
' the correct input parameters
' for the Win32_Process.Create call.
' The InParameters object is an 
' SWbemObject object, so SWbemObject.SpawnInstance_ 
' can be called to create it.

Set oInParams = oProcess.Methods_("Create"). _
    InParameters.SpawnInstance_
oInParams.CommandLine = "Notepad.exe"

' Create sink to receive event resulting
' from the ExecMethodAsync call.
set Sink = wscript.CreateObject( _
    "WbemScripting.SWbemSink","Sink_")

' Call SWbemServices.ExecMethodAsync
' with the WMI path Win32_Process.

bDone = false
Services.ExecMethodAsync Sink, _
     "Win32_Process", "Create", oInParams

' Call the Win32_Process.Create method asynchronously.
' Set up a wait so the results of the method
' execution can be returned to 
' the sink subroutines.

while not bDone    
    wscript.sleep 1000  
wend

' Sink subroutines
sub Sink_OnObjectReady(oOutParams, oContext)
    wscript.echo "Sink_OnObjectReady subroutine " _ 
        &VBCR & "ReturnValue = " _
        & oOutParams.ReturnValue &VBCR & _
        "ProcessId = " & oOutParams.ProcessId
end sub

sub Sink_OnCompleted(HResult, LastErrorObj, oContext)
    wscript.echo "Sink_OnCompleted subroutine, hresult = " _
        & hex(HResult)
    bdone = true
end sub

Requirements

Requirement	Value
Minimum supported client	Windows Vista
Minimum supported server	Windows Server 2008
Header	Wbemdisp.h
Type library	Wbemdisp.tlb
DLL	Wbemdisp.dll
CLSID	CLSID_SWbemServices
IID	IID_ISWbemServices

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