No Source Code Available for Current Location

I've been getting this message when stepping into a WebService method from my application. I've confirmed that all my project references are current and get build when i compile the webservice.

I've pinpointed this down to a specific piece of code but cannot figure out what specifically is causing this...

I have a LIB that contains a class named Extensions.cs. This class is going to contain extension methods. I have 1 extension method and it is defined as such

Code:

---

public static TDerived CreateFromEnumerable<TDerived, T>(this IEnumerable<T> list) where TDerived : List<T>, new()
    {
      TDerived outList = new TDerived();
      outList.AddRange(list);
      return outList;
    }

---

In my WebService i have the "using" statement defined and I have that LIB as a project reference.

Here is how that extension method is used...

Code:

---

micrRecords = micrRecords.Where(tmp => tmp.CheckSystemSequence == request.ImageKey)
              .CreateFromEnumerable<List<MicrRecord>, MicrRecord>();

---

When this line of code is commented out, i never see the "No Source code Available" message, but when enabled, i get it "When trying to ONLY step into the method". Even though i get the message, I can still step into the webservice and even step into that Extension Method.

So, I'm trying get this message to quit displaying because I'm trying to prevent junior developers for being stumped on this message for when there is no necessary need for it.