Hello,
I have found a significant performance issue when using lost of Shared parts. 50% of composition time is spent inside System.Composition.Hosting.Util.SmallSparseInitonlyArray.Add on string.Format calls. The error is obvious: the method has 2 calls like
```
Assumes.IsTrue(e.Index != index, string.Format("An item with the key '{0}' has already been added.", index));
```
No matter what the condition is, string.Format gets evaluated every time.
So, MEF is spending 50% time on producing garbage. Definitely not the task a high performance framework should do. :)
I have found a significant performance issue when using lost of Shared parts. 50% of composition time is spent inside System.Composition.Hosting.Util.SmallSparseInitonlyArray.Add on string.Format calls. The error is obvious: the method has 2 calls like
```
Assumes.IsTrue(e.Index != index, string.Format("An item with the key '{0}' has already been added.", index));
```
No matter what the condition is, string.Format gets evaluated every time.
So, MEF is spending 50% time on producing garbage. Definitely not the task a high performance framework should do. :)