USD: Remove individual hosted control parameters from memory

In our Unified Service Desk implementation (by the way, we’re live and everyone’s happy–YAY!), we are using a particular technique for showing the same entity type on multiple tabs. The nitty-gritty on how to do that is in this article I wrote a while ago.

The TL;DR on this is that we create more than one hosted control for a particular entity. When the entity record is requested, there’s a set of navigation rules that start looking at the URL parameter of the hosted controls, one by one. So if the first hosted control URL is empty, it loads that one, opening a new tab. Let’s say you call another record of the same entity type. It goes again through the navigation rules, checks the URL of the first hosted control, finds that it’s not blank or null, and then the next rule is fired, checking the URL for the second hosted control. If it finds it empty, then it loads that control in a new tab.

So much for a brief description.

When you close a tab, the hosted control parameters are kept in memory. One of the issues we found is that once you used a hosted control, if you close it, the control cannot be reused because the code looks for an empty or non-existing URL parameter to load up the different hosted controls. This would cause us to sometimes hit our control limit for that particular entity.

So we needed to clear the URL parameter. How?

The solution implemented is based on our USD custom panel, so it’s not handled via configuration. However, let me add before explaining that there’s a way to clear all parameters from a hosted control. You can do this by using the ClearDataParameter action, passing the parameter “name=topLevelTreeName“, where topLevelTreeName would be the hosted control or entity you want to clear. As it implies, it’ll clear all parameters for that entity; something you might want to do.

In our case, however, we only wanted to clear the URL parameter, and this is how we did it:

First, we set an event handler for the RequestApplicationClose event on the AppHost object:

 protected override void SessionCreatedEvent(Session session)
     session.AppHost.RequestApplicationClose += AppHost_RequestApplicationClose;

This event handler is wired up when a new session is created by overriding the SessionCreatedEvent method, since you have an AppHost object for every session. Now we need to access the current parameters from the customer record. We do this with the following method:

private Dictionary<string, CRMApplicationData> GetApplicationParameters(string applicationName = "")
    var customerRecord =
            ((AgentDesktopSession) localSessionManager.ActiveSession).Customer.DesktopCustomer;
    if (customerRecord == null) return null;
    if (applicationName != "")
        return customerRecord.CapturedReplacementVariables[applicationName];
    var completeParameterList = new Dictionary<string, CRMApplicationData>();
    foreach (var appName in customerRecord.CapturedReplacementVariables.Keys)
        var appParameterList = customerRecord.CapturedReplacementVariables[appName];
        foreach (var entry in appParameterList)
            completeParameterList.Add(entry.Key, entry.Value);
    return completeParameterList;

This method returns all the existing parameters for the current customer record. We kept it generic so that we can reuse it for any future mad ideas we might have. Now we code in the new event handler for RequestApplicationClose:

private void AppHost_RequestApplicationClose(IHostedApplication app)
    var applicationParameters = GetApplicationParameters(app.ApplicationName);
    if (applicationParameters.ContainsKey("url"))


Now we just look for the parameter, and kill it with fire. That’s it! This executes pretty fast with no noticeable performance hits; remember that this is set to run when the tab is closed, so the user is not left waiting for a process to run. This is a very easy way to remove parameters with pinpoint precision.

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One thought on “USD: Remove individual hosted control parameters from memory

  1. Mike says:

    Hi Jose!
    You mentioned the ClearDataParameter action. Could you tell which hosted control should this action be created on, i couldn’t find anything about it in the sdk. Your approach looks good, but i’m just curious if it can be implemented with just configuration. Will it clear all data parameters just for that “instance” of control? I mean will it not affect the same control in other sessions context?


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