T ReadIfExistsById<T>(
	IdQuery<T> idQuery,
	ITransaction tx,
	long timeout,
	ReadModifiers modifiers
)

Function ReadIfExistsById(Of T) ( _
	idQuery As IdQuery(Of T), _
	tx As ITransaction, _
	timeout As Long, _
	modifiers As ReadModifiers _
) As T

generic<typename T>
T ReadIfExistsById(
	IdQuery<T>^ idQuery, 
	ITransaction^ tx, 
	long long timeout, 
	ReadModifiers modifiers
)

J# supports the use of generic APIs, but not the declaration of new ones.