CreateInstance throws cannot load type

Question

So we have a over 33 VB6 COM+ component which we are migrating to C#. Within these VB6 components we are capturing the dll name, classname, and parameters into a csv file.

I've written a unit test to read this csv file and to dynamically load the VB6 dll via CreateComInstanceFrom.

All of these COM+ components implement 1 of 2 interfaces, either an IQuery or IUpdate. I call IsAssignableFrom to determine which interface it is using and then call the appropriate method.

This works fine. Now comes the C# side.

The migrated C# COM+ component does not want to load dynamically.

I've got the following code             

                    System.Reflection.Assembly _assembly; 
                    _assembly = System.Reflection.Assembly.LoadFrom(assembly.CSharpAssemblyName);
                    CSharptype = _assembly.GetType(vb6Class.CSharpClassName);

                    CSharpcsimClass = _assembly.CreateInstance(CSharptype.FullName, true);
                    //CSharpcsimClass = Activator.CreateInstance(CSharptype);

So my assembly.CSharpAssemblyName is the following - C:\\Projects\\bin\\MDRX.PM.Server.RegQrySvr.dll

It generates the _assembly object with no errors.

{MDRX.PM.Server.RegQrySvr, Version=1.0.141.0, Culture=neutral, PublicKeyToken=5429b6a38ddbad39}

Then I call GetType passing in the name of the class I want - RegQrySvr.RegQueryRegInfoByPatient

It also executes successfully

CSharptype = {Name = "RegQueryRegInfoByPatient" FullName = RegQrySvr.RegQueryRegInfoByPatient"}

But then the CreateInstance fails

Message = "Cannot load type 'RegQrySvr.RegQueryRegInfoByPatient, MDRX.PM.Server.RegQrySvr, Version=1.0.141.0, Culture=neutral, PublicKeyToken=5429b6a38ddbad39'."

If I add a reference to my project to MDRX.PM.Server.RegQrySvr.dll, this set will execute successfully, but I don’t want to add the reference since we will have 33 COM+ components once all these VB6 components are migrated

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Joe Pacelli

Answer 1

What is the type declaration for the variable, CSharpcsimClass, and how are you declaring it?  What type should it be, Object or something else?  It seems that it should be a type defined within your RegQrySrv assembly.

Rudy   =8^D

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Mark the best replies as answers. "Fooling computers since 1971."

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Answer 2

CSharpcsimClass is defined as object because it can be any one of the 33 COM+ components.

I change the output directory of this project to be the same directory this assembly reside's in and now instead of the cannot load type. I get the following error.

Message = "Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))"

Only change I did was putting this output in the same directory as my COM+ component output.

I get this message regardless of how I try to create it

                    CSharpcsimClass = _assembly.CreateInstance(CSharptype.FullName, true);
                    //CSharpcsimClass = Activator.CreateInstanceFrom(assembly.CSharpAssemblyName, vb6Class.CSharpClassName);
                    //CSharpcsimClass = Activator.CreateComInstanceFrom(assembly.CSharpAssemblyName, vb6Class.CSharpClassName).Unwrap();

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Joe Pacelli

Answer 3

That error might be a result of where the assembly is located, off of the root directory.  I think it is a security violation from the OS.

http://windows.microsoft.com/en-US/Windows7/How-do-I-open-a-file-if-I-get-an-access-denied-message  

http://blogs.msdn.com/b/astebner/archive/2005/08/16/452523.aspx  

Rudy   =8^D

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Mark the best replies as answers. "Fooling computers since 1971."

http://thesharpercoder.blogspot.com/

Answer 4

Does the RegQrySvr.RegQueryRegInfoByPatient class is public and have a public parameterless constructor ?

Answer 5

Yes it has a public parameterless constructor and the class itself is public.

At one point it ran yesterday. Now it's back to the first error message I received

Message = "Cannot load type 'RegQrySvr.RegQueryRegInfoByPatient, MDRX.PM.Server.RegQrySvr, Version=1.0.141.0, Culture=neutral, PublicKeyToken=5429b6a38ddbad39'."

I moved all the output directories to be the same, so all dll's are in the same directory now. So I'm not sure why I get this error

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Joe Pacelli

Answer 6

Make sure that the assembly version that your project is looking for matches the version of the file that is being found.

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Mark the best replies as answers. "Fooling computers since 1971."

http://thesharpercoder.blogspot.com/

Answer 7

For the access denied error, when reproducing the issue, please use process monitor tool (http://technet.microsoft.com/en-us/sysinternals/bb896645.aspx) to log file/registry activities of your app, and then you can analyze the file/registry activities log to find out which file (or registry key) your app is trying to access with insufficient permission.

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Regards,
Eric Yang
Microsoft Online Community Support