Duplicate Objects detected for Instance of Type

[Alexander Dolin]

Hi,

I'm getting the following exception from structure map -  "Duplicate Objects detected for Instance d54e25dc-d19c-4d70-99d1-56bd2502d203 of Type ..."

The stack trace is:

at StructureMap.InstanceCache.Set(Type pluginType, Instance Instance, Object result) in c:\code\structuremap\Source\StructureMap\InstanceCache.cs:line 60
at StructureMap.BuildSession.CreateInstance(Type pluginType, Instance instance) in c:\code\structuremap\Source\StructureMap\BuildSession.cs:line 159
at StructureMap.BuildSession.<>c_DisplayClass3.<.ctor>b_1() in c:\code\structuremap\Source\StructureMap\BuildSession.cs:line 34
at StructureMap.BuildSession.CreateInstance(Type pluginType) in c:\code\structuremap\Source\StructureMap\BuildSession.cs:line 192
at StructureMap.BuildSession.GetInstance[T]() in c:\code\structuremap\Source\StructureMap\BuildSession.cs:line 78

This exception happens only from time to time and is very difficult to reproduce.

What I've found out so far:

Calling ObjectFactory.Container.GetInstance(type) will create a new BuildSession with a new non-static cache.

The call will reach BuildSession.CreateInstance(Type pluginType, Instance instance) and no instance is in the cache yet. (https://github.com/structuremap/structuremap/blob/master/Source/StructureMap/BuildSession.cs 147)

Now we'll go on to _builder.Resolve(pluginType, instance, this);

Somewhere during Resolve() the object will get into the cache and later in CreateInstance we're saving it into the cache once again, receiving the exception.

That object is configured with Singleton lifecycle. The application is WCF service hosted in IIS.

I still cannot understand why sometimes that object gets into the cache twice.

I'd like to ask for all the possible ways how this can happen in SM.

Thank you.