"No valid exports were found that match the constraint" in Release, but not Debug

Hello all. I am using VS2010 with .NET 4

I have some code that looks in a directory for any dlls and then finds the one that contains the correct exports and reads it in.

The code is below:

Code:

---


var catalog = new AggregateCatalog();
_container = new CompositionContainer(catalog);
string exePath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
string roofcalcPath = Path.Combine(exePath, "roofcalc");
if (Directory.Exists(roofcalcPath))
{
        try
        {
        // where to find the calculator DLL
                    try
                    {
                        catalog.Catalogs.Add(new DirectoryCatalog(roofcalcPath));
                    }
                    catch (ReflectionTypeLoadException rtle)
                    {
                        Type[] err = rtle.Types;

                    }
        // Load calculator DLL, create and store reference to object instances
        // that are marked Import in this class.
        _container.ComposeParts(this);
}
catch (System.ComponentModel.Composition.ChangeRejectedException)
{
        // expected exception of calculator DLL is not present in the directory
                                        Calculator = null;
}
}

---

The dll that I'm trying to load implements the proper interface

Code:

---

    [Export(typeof(IRoofCalc))]
    public class GPiStructHelper : IRoofCalc
    {
        /// <summary>
        /// Call this from iStruct to pass in the structural data and
        /// return a list of reaction loads to be further processed by iStruct
        /// </summary>
        /// <param name="structureData"></param>
        /// <returns></returns>
        ResultData IRoofCalc.CalculateReactions(StructureData structureData)
        {
            //convert iStruct data to GP data
            GPHelperClass.ImportData(structureData);

            //Design each member
            List<GPRoofMember> rfMembers = new List<GPRoofMember>();
            List<GPColumnBracing> cols = new List<GPColumnBracing>();
            List<GPStrongback> strgbks = new List<GPStrongback>();

            foreach (KeyValuePair<long, GPObject> gpObject in StaticGPiStructHelper.StructuralItems)
            {
                if (gpObject.Value is GPRoofMember)
                {
                    GPRoofMember target = gpObject.Value as GPRoofMember;
                    rfMembers.Add(target);
                }
                if (gpObject.Value is GPStrongback)
                {
                    GPStrongback stbk = gpObject.Value as GPStrongback;
                    if (!stbk.IsWall)
                        strgbks.Add(stbk);
                }
                if (gpObject.Value is GPColumnBracing)
                {
                    GPColumnBracing col = gpObject.Value as GPColumnBracing;
                    if (col.GetOwner() == 0)
                        cols.Add(col);
                }
            }
            foreach(GPRoofMember target in rfMembers)
                if (!target.IsDesigned)
                    target.Design();
 
            //Transfer loads for strongbacks and bracing
            foreach (GPStrongback stbk in strgbks)
            {
                stbk.TransferLoads();
            }
            foreach(GPColumnBracing col in cols)
            {
                col.TransferLoads();
            }
       

            //convert data from GP to iStruct
            return GPHelperClass.ExportData();
        }

        Sample IRoofCalc.CalcWithData(Sample samp)
        {
            return null;
        }
 
        string IRoofCalc.Hello()
        {
            string msg = "Not implemented";
            return msg;
        }

    }

---

It works perfectly and is able to read the dll and perform the functions when I use the DEBUG version of the dll, however when I use the RELEASE version I get the following error message

The composition remains unchanged. The changes were rejected because of the following error(s): The composition produced a single composition error. The root cause is provided below. Review the CompositionException.Errors property for more detailed information.

1) No valid exports were found that match the constraint '((exportDefinition.ContractName == "StructuredDesign.RoofCalcInterface.IRoofCalc") AndAlso (exportDefinition.Metadata.ContainsKey("ExportTypeIdentity") AndAlso "StructuredDesign.RoofCalcInterface.IRoofCalc".Equals(exportDefinition.Metadata.get_Item("ExportTypeIdentity"))))', invalid exports may have been rejected.

Resulting in: Cannot set import 'GPAddonTestHarness.Host.Calculator (ContractName="StructuredDesign.RoofCalcInterface.IRoofCalc")' on part 'GPAddonTestHarness.Host'.
Element: GPAddonTestHarness.Host.Calculator (ContractName="StructuredDesign.RoofCalcInterface.IRoofCalc") --> GPAddonTestHarness.Host


Please help me figure out what the heck is going on.