If we deal with non thread safe managed code at concurrent environment, we can create
AppDomain that loads the non thread safe assembly and call the code. CLR isolates
code between AppDomain(s). This means CLR will keep seperate instances of the code
for each AppDomain. (If you have 10 AppDomain using the code, CLR will load 10 instance
of the code).

However, I have unmanaged/non thread safe dll. I need to konw how to use it inside
.Net code with concurrent enviornment. I can not find any article dealing with this situation.

Any advice is appreciated.