"AccessViolationException" when calling to "Marshal.PtrToStringAuto"

i used external methods resolve mx records of several domains,
but, i'm getting "system.accessviolationexception" not caught try catch block!

i'm working code last couple of years, possible update caused error.

strange 1 server out of 12 throws error.

here code:

  private static list<string> _getmxrecords(string domain)      {        if (environment.osversion.platform != platformid.win32nt)          return null;          list<string> results = new list<string>();          intptr ptr1 = intptr.zero;        intptr ptr2 = intptr.zero;        int errorcode = dnsquery(ref domain, querytypes.dns_type_mx, queryoptions.dns_query_bypass_cache, 0, ref ptr1, 0);        if (errorcode != 0) return null;          mxrecord recmx;        for (ptr2 = ptr1; !ptr2.equals(intptr.zero); ptr2 = recmx.pnext)        {          recmx = (mxrecord)marshal.ptrtostructure(ptr2, typeof(mxrecord));            string record = marshal.ptrtostringauto(recmx.pnameexchange); //////////////////// <-- exception occurs here //////////////////////////          if (record.length > 3) results.add(record);        }        dnsrecordlistfree(ptr1, 0);          if (results.count == 0) return null;          return results;      }  

      [dllimport("dnsapi", entrypoint = "dnsquery_w", charset = charset.unicode, setlasterror = true, exactspelling = true)]      private static extern int dnsquery([marshalas(unmanagedtype.vbbyrefstr)]ref string pszname, querytypes wtype, queryoptions options, int aipservers,        ref intptr ppqueryresults, int preserved);            [dllimport("dnsapi", charset = charset.auto, setlasterror = true)]      private static extern void dnsrecordlistfree(intptr precordlist, int freetype);        private enum queryoptions      {        dns_query_bypass_cache = 8      }        private enum querytypes      {        dns_type_mx = 15      }        [structlayout(layoutkind.sequential)]      private struct mxrecord      {        public intptr pnext;        public string pname;        public short wtype;        public short wdatalength;        public int flags;        public int dwttl;        public int dwreserved;        public intptr pnameexchange;        public short wpreference;        public short pad;      }  

the "eventviewer" shows error eventid: 1026

framework version: v4.0.30319  description: process terminated due unhandled exception.  exception info: system.accessviolationexception  stack:    @ microsoft.win32.win32native.copymemoryuni(system.text.stringbuilder, intptr, intptr)    @ system.runtime.interopservices.marshal.ptrtostringuni(intptr)  

and "application error" this:

faulting application xxxxxx.exe, version x.0.0.0, faulting module ntdll.dll, version 5.2.3790.4789, fault address 0x0001bdb2.  

i tried (after searching google side down):

1. uncheck "suppress jit optimization on module load"

2. change "platform target" "x86"

3. add "try catch" block @ main application , register "appdomain.currentdomain.unhandledexception" event (which doesn't raise!!)

4. check "p/invoke" signatures 

5. frustrated :)

 

i'm using windows 2003 web edition (32 bit).

 

thank you!!

i solved it, want update gets here same problem..

 

you need add attribute called "handleprocesscorruptedstateexceptionsattribute" @ declaration of method calls external method in order redirect exception application, like:

[handleprocesscorruptedstateexceptionsattribute()]   private static list<string> _getmxrecords(string domain)   {     ...   }

good luck!

evyatar

.NET Framework  >  Common Language Runtime Internals and Architecture