System.Threading.ExecutionContextSwitcher.UndoNoThrow C# (CSharp) Method

        internal bool UndoNoThrow()
        {
            try
            {
                Undo();
            }
            catch
            {
                return false;
            }
            return true;
        }
        

        internal static ExecutionContextSwitcher SetExecutionContext(ExecutionContext executionContext)
        {
            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;

            BCLDebug.Assert(executionContext != null, "ExecutionContext cannot be null here.");


            // Set up the switcher object to return;
            ExecutionContextSwitcher ecsw = new ExecutionContextSwitcher();

            ecsw.thread = Thread.CurrentThread;
            ecsw.prevEC = Thread.CurrentThread.GetExecutionContextNoCreate(); // prev
            ecsw.currEC = executionContext;                                   //current

            // Update the EC on thread
            Thread.CurrentThread.SetExecutionContext(executionContext);

            RuntimeHelpers.PrepareConstrainedRegions();
            try
            {
                if (executionContext != null)
                {
                    //set the security context
                    SecurityContext sc = executionContext.SecurityContext;
                    if (sc != null)
                    {
                        // non-null SC: needs to be set
                        SecurityContext prevSeC = (ecsw.prevEC != null) ? ecsw.prevEC.SecurityContext : null;
                        ecsw.scsw = SecurityContext.SetSecurityContext(sc, prevSeC, ref stackMark);
                    }
                    else if (!SecurityContext.CurrentlyInDefaultFTSecurityContext(ecsw.prevEC))
                    {
                        // null incoming SC, but we're currently not in FT: use static FTSC to set
                        SecurityContext prevSeC = (ecsw.prevEC != null) ? ecsw.prevEC.SecurityContext : null;
                        ecsw.scsw = SecurityContext.SetSecurityContext(SecurityContext.FullTrustSecurityContext, prevSeC, ref stackMark);
                    }

                    // set the sync context
                    SynchronizationContext syncContext = executionContext.SynchronizationContext;
                    if (syncContext != null)
                    {
                        SynchronizationContext prevSyC = (ecsw.prevEC != null) ? ecsw.prevEC.SynchronizationContext : null;
                        ecsw.sysw = SynchronizationContext.SetSynchronizationContext(syncContext, prevSyC);
                    }

                    // set the Host Context
                    HostExecutionContext hostContext = executionContext.HostExecutionContext;
                    if (hostContext != null)
                    {
                        ecsw.hecsw = HostExecutionContextManager.SetHostExecutionContextInternal(hostContext);
                    }
                }
            }
            catch
            {
                ecsw.UndoNoThrow();
                throw;
            }
            return(ecsw);
        }