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IWMDeviceManager2::EnumDevices2

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The EnumDevices2 method retrieves an enumeration interface that is used to enumerate portable devices connected to the computer.

Microsoft strongly recommends that applications use the EnumDevices2 method instead of IWMDeviceManager::EnumDevices.

Syntax

HRESULT EnumDevices2(IWMDMEnumDevice**ppEnumDevice);

Parameters

ppEnumDevice

[out]  Pointer to a pointer to an IWMDMEnumDevice interface. The caller is responsible for calling Release on the retrieved interface.

Return Values

The method returns an HRESULT. All the interface methods in Windows Media Device Manager can return any of the following classes of error codes:

  • Standard COM error codes
  • Windows error codes converted to HRESULT values
  • Windows Media Device Manager error codes

For an extenstive list of possible error codes, see Error Codes.

Possible values include, but are not limited to, those in the following table.

Return code Description
S_OK The method succeeded.
E_INVALIDARG The ppEnumDevice parameter is an invalid or NULL pointer.
E_FAIL An unspecified error occurred.

Remarks

This method returns an enumerator that takes advantage of the Plug and Play (PnP) system for a faster enumeration and lower memory use. For PnP-complaint service providers, it loads in memory only those service providers that have a device currently connected to the computer, and requests only those service providers to create device objects.

This method returns a snapshot of the devices connected when the underlying object was first created. To ensure that the device list is up to date, call Reinitialize before calling this method.

Example Code

The following C++ code loops through all the devices and retrieves the display name of each.

// Enumerate through the devices using the faster EnumDevices2 Plug-and-Play method.
// IWMDevMgr2 is a global IWMDeviceManager2 pointer.
CComPtr<IWMDMEnumDevice> pEnumDevice;
hr = pIWMDevMgr2->EnumDevices2(&pEnumDevice);
if (hr == S_OK)
{
    // Length of all the strings we'll send in. 
    const UINT MAX_CHARS = 100;
    WCHAR name[MAX_CHARS];

    // Enumerate through devices using a dummy loop.
    while(TRUE)
    {
        // Get a device handle.
        IWMDMDevice* pDevice;
        ULONG ulFetched = 0;
        hr = pEnumDevice->Next(1, &pDevice, &ulFetched);
        CComQIPtr<IWMDMDevice2> pDevice2(pDevice);

        if (hr != S_OK || ulFetched != 1)
        {
            break;
        }
        ZeroMemory(name, MAX_CHARS);
        hr = pDevice2->GetName(name, MAX_CHARS);
    }
}

Requirements

Header: Defined in mswmdm.h.

Library: mssachlp.lib

See Also