## IGraphVersion Interface

The IGraphVersion interface is provided by the filter graph manager to let other objects, especially plug-in distributors and the Graphedt.exe tool, know when the graph has changed.

When to Implement

This interface is implemented by the filter graph manager.

When to Use

Use this interface if your application or plug-in distributor must know when filters have been added, deleted, or reconnected.

Methods in Vtable Order

IUnknown methods | Description
QueryInterface | Returns pointers to supported interfaces.
AddRef | Increments the reference count.
Release | Decrements the reference count.

IGraphVersion methods | Description
QueryVersion | Returns the current graph version number.

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IGraphVersion::QueryVersion

IGraphVersion Interface

Returns the current graph version number.

HRESULT QueryVersion(
LONG* pVersion
);

##### Parameters

pVersion
  Current graph version.

##### Return Values

Returns an HRESULT value that depends on the implementation. HRESULT can be one of the following standard constants, or other values not listed:

Value | Meaning
E_FAIL | Failure.
E_POINTER | Null pointer argument.
E_INVALIDARG | Invalid argument.
E_NOTIMPL | Method isn't supported.
S_OK or NOERROR | Success.

##### Remarks

The version number is incremented every time there is a change in the set of filters in the graph or in their connections. If the version number has changed since the last enumeration, the graph must be re-enumerated.

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