http://blogs.msdn.com/b/arvindsh/archive/2012/10/03/a-curious-case-clr-com-interop-leak.aspx&#160; Background A customer asked me a question last week: in CLR-COM interop case, who is responsible to free up a string returned from COM? My understanding was that the interop layer setup by .NET will automatically take care of this. However, I thoughtenTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)http://blogs.msdn.com/b/arvindsh/archive/2012/10/03/a-curious-case-clr-com-interop-leak.aspx#10400390Thu, 07 Mar 2013 18:09:33 GMT91d46819-8472-40ad-a661-2c78acb4018c:10400390Arkady<p>Method SayHello is defined as [out] in IDL. At the same time the call from C# uses ref. </p> <p>1. Is it what automatically generated in interop dll?</p> <p>2. Do you still have a leak if you use SayHello(out sout); in C#?</p> <p>3. Do you still have a leak if you set sout to null before passing to SayHello?</p> <p>string sout = null;</p> <p>SayHello(out sout);</p> <div style="clear:both;"></div><img src="http://blogs.msdn.com/aggbug.aspx?PostID=10400390" width="1" height="1">http://blogs.msdn.com/b/arvindsh/archive/2012/10/03/a-curious-case-clr-com-interop-leak.aspx#10357798Tue, 09 Oct 2012 15:01:23 GMT91d46819-8472-40ad-a661-2c78acb4018c:10357798Lucian Bargaoanu<p>The parameter is ref, so in and out. This means that the COM server should free it before using it as an out parameter. I think this is the root cause of the problem.</p> <div style="clear:both;"></div><img src="http://blogs.msdn.com/aggbug.aspx?PostID=10357798" width="1" height="1">http://blogs.msdn.com/b/arvindsh/archive/2012/10/03/a-curious-case-clr-com-interop-leak.aspx#10355826Thu, 04 Oct 2012 09:06:15 GMT91d46819-8472-40ad-a661-2c78acb4018c:10355826Arvind Shyamsundar<p>Yes, I have confirmed by 2 observations: the sample application, left unmodified, will run to a state where it exhausts all address space (~2GB in x86). Secondly, a GC.Collect makes no difference to this scenario.</p> <div style="clear:both;"></div><img src="http://blogs.msdn.com/aggbug.aspx?PostID=10355826" width="1" height="1">http://blogs.msdn.com/b/arvindsh/archive/2012/10/03/a-curious-case-clr-com-interop-leak.aspx#10355811Thu, 04 Oct 2012 07:58:10 GMT91d46819-8472-40ad-a661-2c78acb4018c:10355811Thomas Olsson<p>Are you sure that these are not cleared at the next GC?</p> <div style="clear:both;"></div><img src="http://blogs.msdn.com/aggbug.aspx?PostID=10355811" width="1" height="1">