<ExtensionAttribute()>
Public Shared Function FirstPageAsync(Of T)( _
   ByVal source As IPager(Of T), _
   ByVal onSuccess As Action(Of Page(Of T)), _
   ByVal onFail As Action(Of Exception) _
) As PageOperationResult(Of T)

Dim source As IPager(Of T)
Dim onSuccess As Action(Of Page(Of T))
Dim onFail As Action(Of Exception)
Dim value As PageOperationResult(Of T)
 
value = Compatibility.FirstPageAsync(Of T)(source, onSuccess, onFail)

[ExtensionAttribute()]
public static PageOperationResult<T> FirstPageAsync<T>( 
   IPager<T> source,
   Action<Page<T>> onSuccess,
   Action<Exception> onFail
)

[ExtensionAttribute()]
public:
static PageOperationResult<T^>^ FirstPageAsyncgeneric<typename T>
( 
   IPager<T^>^ source,
   Action<Page<T^>^>^ onSuccess,
   Action<Exception^>^ onFail
)