Function IsPackageInstalled ( _
    ByRef guidPackage As Guid, _
    <OutAttribute> ByRef pfInstalled As Integer _
) As Integer

Dim instance As IVsShell
Dim guidPackage As Guid
Dim pfInstalled As Integer
Dim returnValue As Integer

returnValue = instance.IsPackageInstalled(guidPackage, _
    pfInstalled)

int IsPackageInstalled(
    ref Guid guidPackage,
    out int pfInstalled
)

int IsPackageInstalled(
    [InAttribute] Guid% guidPackage, 
    [OutAttribute] int% pfInstalled
)

function IsPackageInstalled(
    guidPackage : Guid, 
    pfInstalled : int
) : int