How do I detect if XenApp Client is installed on user machine?

We are upgrading from Citrix Metaframe to XenApp, and I need to know if there's a way to programmatically detect if the XenApp Web Plugin v11.0 is already installed on a client machine when it contacts our webserver for login -- this was previously done for the Metaframe Web Client by attempting to instantiate the ICA client in an ASP script, which used the result开发者_如何学Pythons to determine whether to offer the client as a download/install.

The current code for this detection is:

Set icaObj = CreateObject("Citrix.ICAClient")

The above code does not find the XenApp plugin.

I continued my research after posting this question and I finally found the answer. Only 3 views on this question since I posted it, but despite the disinterest I believe I should answer my question, "Just in Case" someone else has this problem.

I was mistaken in my statement in question that the code I posted didn't find the XenApp plugin. In fact, it does. It returns a valid object in the presence of both Metaframe and XenAppWeb. I posted this question on Citrix's own forums, and no answers there either.

What I did to find the answer was to create a VS2008 project to which I added a COM reference to the Citrix ICA library -- both of them, installed separately one at a time. I found that both had a COM library named WFICALib, and searched through both of them to see if there was something that might distinguish them. What I found was a property, ClientVersion, which was 9.0.xxx for Metaframe, and 11.0.xxxx for XenAppWeb.

BINGO!

From this I cut the following code to return the version as a function in VBScript:

Function GetVer()
    Dim icaObj, Ver
    On Error Resume Next
    Set icaObj = CreateObject("Citrix.ICAClient")
    if err.number = 0 then
        if IsObject(icaObj) then
           GetVer = icaObj.ClientVersion
        else
           GetVer = 0
        end if
        set icaObj = nothing
    else
        GetVer = 0
    end if
End Function

ADDENDUM:

Since posting this answer, I have discovered that this script in the newer versions of Internet Explorer (e.g. IE9) is not reliably detecting the plugin -- sometimes it worked, and other times not! What I did to fix the problem was to switch the script to JScript instead of JavaScript, and the new version looks like this:

<script type="text/jscript">
    function GetCitrixVersion() {
        try {
            var icaObj = new ActiveXObject("Citrix.ICAClient");
            return icaObj.ClientVersion;
        }
        catch (e) {
            return 0;
        }
    }
</script>

Note the script type is text/jscript, not text/javascript.