Programmatically Activating Features just after Deployment

There are a variety of scenarios where features need to be programmatically activated just after a solution has been deployed.  I have found that even when the SPSolution object says it has been deployed, it really isn’t finished deploying.  Sometimes my SPFeatureDefinitions are either non existents or not installed even when the deployment is “done”.  They eventually do show up. Until they do, feature activation fails when the feature is added to the SPFeatureCollection of the SPFarm, SPWebApplication, SPSite, or SPWeb.  I ended up coding a small bit of code to work around this problem.  This example shows activation of a web application scope feature, but the algorithm can be applied to a feature of any scope.

private void ActivateWebApplicationFeature(Uri webApplicaitonUri, Guid featureId, int timeoutSeconds)
{
    const int sleepTime = 1000;
    for (int i = 0; i < timeoutSeconds; i++)
    {
        try
        {
            SPFeatureDefinition definition = SPFarm.Local.FeatureDefinitions[featureId];
            if (definition.Status == SPObjectStatus.Online)
            {
                break;
            }
            Thread.Sleep(sleepTime);
        }
        catch
        {
            Thread.Sleep(sleepTime);
        }
    }
    SPWebApplication application = SPWebApplication.Lookup(webApplicaitonUri);
    if (application.Features[featureId] == null)
    {
        AddWebApplicationFeature(webApplicaitonUri, featureId);
    }
}

private void AddWebApplicationFeature(string webApplicaitonUri, Guid featureId)
{
    int count = 0;
    while (true)
    {
        try
        {
            SPWebApplication application = SPWebApplication.Lookup(webApplicaitonUri);
            application.Features.Add(featureId);
            application.Update();
            break;
        }
        catch (SPDeletedConcurrencyException)
        {
            // Done. This object is gone so we are finished.
            // Optional logging of condition
            break;
        }
        catch (SPUpdatedConcurrencyException)
        {
            count++;
            if (count > 10)
            {
                throw;
            }
        }
    }
}

The algorithm is to first wait for the feature definition to appear.   When looking up the SPFeatureDefinition in the SPFeatureDefinitionCollection an exception will be thrown until the definition has been added.  The code waits a second between checks.  It continues waiting for the SPFeatureDefinition to install.  Finally it activates the feature if the feature needs activation (in certain upgrade scenarios the feature may already be active).  You will notice that the second method uses my technique to control SPDeletedConcurrencyException and SPUpdatedConcurrencyException.