Microsoft.VisualStudio.Project.ProjectContainerNode.CloseChildren C# (CSharp) Method

        public virtual int CloseChildren()
        {
            int returnValue = VSConstants.S_OK; // be optimistic.

            IVsSolution solution = this.GetService(typeof(IVsSolution)) as IVsSolution;
            Debug.Assert(solution != null, "Could not retrieve the solution from the services provided by this project");

            if(solution == null)
            {
                return VSConstants.E_FAIL;
            }

            IntPtr iUnKnownForSolution = IntPtr.Zero;

            try
            {
                iUnKnownForSolution = Marshal.GetIUnknownForObject(solution);

                // notify SolutionEvents listeners that we are about to close children
                IVsFireSolutionEvents fireSolutionEvents = Marshal.GetTypedObjectForIUnknown(iUnKnownForSolution, typeof(IVsFireSolutionEvents)) as IVsFireSolutionEvents;
                ErrorHandler.ThrowOnFailure(fireSolutionEvents.FireOnBeforeClosingChildren(this));

                // If the removal crashes we never fire the close children event. IS that a problem?
                this.RemoveNestedProjectNodes();

                ErrorHandler.ThrowOnFailure(fireSolutionEvents.FireOnAfterClosingChildren(this));
            }
            finally
            {
                if(iUnKnownForSolution != IntPtr.Zero)
                {
                    Marshal.Release(iUnKnownForSolution);
                }
            }

            return returnValue;
        }