Question
Singleton Per Call Context (Web Request) in Unity
A few days ago, I had an issue with ASP.Net threading. I wanted to have a singleton object per web request. I actually need this for my unit of work. I wanted to instantiate a unit of work per web request so that identity map is valid through out the request. This way I could use an IoC to inject my own IUnitOfWork to my repository classes transparently, and I could use the same instance to query and then update my entities.
Since I am using Unity, I mistakenly used PerThreadLifeTimeManager. I soon realised that ASP.Net threading model does not support what I want to achieve. Basically it uses a threadpool and recycles threads, and that means that I get one UnitOfWork per thread!! However, what I wanted was one unit of work per web request.
A bit of googling gave me this great post. That was exactly what I wanted; except for the unity part which was quite easy to achieve.
This is my implementation for PerCallContextLifeTimeManager for unity:
public class PerCallContextLifeTimeManager : LifetimeManager
{
private const string Key = "SingletonPerCallContext";
public override object GetValue()
{
return CallContext.GetData(Key);
}
public override void SetValue(object newValue)
{
CallContext.SetData(Key, newValue);
}
public override void RemoveValue()
{
}
}
And of course I use this to register my unit of work with a code similar to this:
unityContainer
.RegisterType<IUnitOfWork, MyDataContext>(
new PerCallContextLifeTimeManager(),
new InjectionConstructor());
Hope it saves someone a bit of time.