IDSF::ReadState Method

项目
09/21/2010

The ReadState method reads the stored public state of a driver.

Syntax

HRESULT ReadState(
  [in]           DSFStateType Type,
  [in]           BSTR Guid,
  [out, retval]  DSFPropertyBag **ppDSFPropertyBag
);

Parameters

Type [in]
The type of state to read.
Guid [in]
The GUID of the driver whose state is to be read.
ppDSFPropertyBag [out, retval]
The property bag to contain the state.

Return Value

ReadState returns one of the following values:

Return code	Description
S_OK	The public state was read correctly.
E_INVALIDARG	The Type parameter is not a valid DSFDefaultStateType value. This method can also return many standard COM return values.
E_POINTER	The ppDSFPropertyBag parameter is not a valid pointer.

S_OK

The public state was read correctly.

E_INVALIDARG

The Type parameter is not a valid DSFDefaultStateType value.

This method can also return many standard COM return values.

E_POINTER

The ppDSFPropertyBag parameter is not a valid pointer.

Remarks

The current release of DSF supports only DSFDefaultStateType as the state type.

Examples

The following C++ code example shows you how to read a driver's public state.

HRESULT CMyDevice::ReadSaveState(BSTR bstrGuid, IDSFPropretyBag *piDSFPropertyBag)
{
 DSFStateType Type  = DSFDefaultStateType;
      HRESULT         hr       = S_OK;

     //Read the saved state for this device
 hr = m_piDSFObject->ReadState(Type, bstrGuid, reinterpret_cast<DSFPropertyBag**>(&piDSFPropertyBag));

 return hr;
}

Requirements

Header

DSFif.h

通过