Microsoft.VisualStudio.Project.OutputGroup.InvalidateGroup C# (CSharp) Method

        public virtual void InvalidateGroup()
        {
            // Set keyOutput to null so that a refresh will be performed the next time
            // a property getter is called.
            if(null != keyOutput)
            {
                // Once the group is invalidated there is no more reason to listen for events.
                project.ProjectPropertyChanged -= new EventHandler<ProjectPropertyChangedArgs>(OnProjectPropertyChanged);
            }
            keyOutput = null;
        }