I recently needed to check to see if a user control was open in the SalesLogix dialog workspace when the page loads. In this scenario the same user control was being used in both the tab workspace and the dialog workspace and depending on which one was being shown I wanted to set visibility of different controls. To determine if the control is in a dialog is simple just this line of code (assuming the user control inherits from the Entity Bound Smart Part class):
if (this.IsInDialog())
{
//We are in a dialog
}
else
{
//We are not in a dialog
}