How to programmatically find if a smart part is present on a page (for example, if the behavior of one smart part depends on whether another smart part is loaded… in my case I wanted to show a button on my smart part ONLY if some other custom smart part had been added to the page):

• If the smart part you need to find is on any workspace but DialogWorkspace, you can use FindControl (or FindControlRecursive – google for the code). Remember the smart part will only show up if it is displayed in the particular mode (for example if it is a Detail mode smart part it won’t be anywhere in List mode)
• If the smart part is on the DialogWorkspace it is a bit trickier. If it is not currently displayed, it won’t be there as a control, but instead it will be in the private variable _mySmartParts of the DialogWorkspace.

So here is my FindSmartPart function:

/// <summary>
/// Find a smart part under the specified work item.
/// If the smart part is not on the page, return null.
/// </summary>
/// <param name="parent"></param>
/// <param name="smartPartId"></param>
/// <returns></returns>
private Control FindSmartPart(UIWorkItem parent, String smartPartId)
{
    foreach (var ws in parent.Workspaces)
    {
        if (ws.Value is DialogWorkspace)
        {
            // in this case peek in _mySmartParts
            FieldInfo field = typeof(DialogWorkspace).GetField("_mySmartParts", BindingFlags.Instance | BindingFlags.NonPublic);
            if (field == null)
                throw new InvalidOperationException("Field _mySmartParts not found in DialogWorkspace");
            Dictionary<object, ISmartPartInfo> smartParts = (Dictionary<object, ISmartPartInfo>)field.GetValue(ws.Value);
            if (smartParts != null)
            {
                foreach (object smartPart in smartParts.Keys)
                {
                    Control c = smartPart as Control;
                    if (c != null && c.ID == smartPartId)
                        return c;
                }
            }
        }

        foreach (var smartPart in ws.Value.SmartParts)
        {
            Control c = (Control)smartPart;
            if (c.ID == smartPartId)
                return c;
        }
    }
    return null;
}

Well, nobody said it would be pretty – but, it gets the job done.