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I have a C# com object that I'm creating which I'm testing in a VB environment. This COM object is also calling other COM objects which were written in VB.
I have a VB COM object with a method who's signature looks like this:
Public Function MyFunction(varNames() As String) As String()
I'm trying to send in a string array when calling this guy in my C# code like this:
string[] sNames = { "ProjectName" };
COMInt.ComClass oCDS = new COMInt.ComClass();<br />
<br />
sValues = oCDS.MyFunction(ref sNames);
I get type mismatch on the "ref sNames". This is just one of many combinations I've tried, but have not quite figured out the correct type match.
Here is the error I receive in VS.Net:
D:\CSS\Dev\ProjName\ProjClass.cs(255): The best overloaded method match for 'COMInt.ComClass.MyFunction(ref System.Array)' has some invalid arguments
Can anybody help me out and explain this?
P.S. Sorry for all the "MyFunction" and "ProjClass", etc.... but this is at work and I could get in trouble just for posting the names of things (they are VERY picky).
There are only 10 types of people in this world....those that understand binary, and those that do not.
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Check the signature of MyFunction. If it doesn't have a ref or out keyword before the param, don't use either ref or out to call the method. Strings in .NET (as well as most other classes) are already reference Types, so you rarely need to use ref or out (sometimes it's necessary, like for pointers to pointers, but it's typically only necessary for value types).
Microsoft MVP, Visual C#
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Yeah, I know what you're saying. The signature was the first code section/line.
I tried it first without the ref, assuming that was the correct way (most of my experience being a C programmer).
That just gave me the same error. This one shows up too:
D:\CSS\Dev\ProjName\ClassName.cs(255): Argument '1': cannot convert from 'string[]' to 'ref System.Array'.
BTW...also to note, the new C# must match the existing VB signature because that is a long time used COM object so interface can't change.
There are only 10 types of people in this world....those that understand binary, and those that do not.
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No, what was the signature in the CCW (the interop assembly) that was generated from the VB COM object? Did it use a ref? The original error message you got indicates that it does not.
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Oh...sorry..I got ya now. And no, it didn't use ref, I didn't think it did. I was only trying that after it didn't work originally without the ref thinking maybe I needed that to send it in.
This is the interop assembly (the type lib you mean I hope...this is my first taste in COM).
SAFEARRAY(BSTR) MyFunction([in, out] SAFEARRAY(BSTR)* varNames);
There are only 10 types of people in this world....those that understand binary, and those that do not.
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No, the assembly generated after running tlbimp.exe on the typelib, or using VS.NET to do the same. Judging by the method declaration, though, you should end up with something like the following:
void MyFunction(
[MarshalAs(UnmanagedType.SafeArray, SafeArraySubType=VarEnum.VT_BSTR)]
string[] varNames,
[MarshalAs(UnmanagedType.SafeArray, SafeArraySubType=VarEnum.VT_BSTR), Out]
string[] retVal);
Microsoft MVP, Visual C#
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Sorry...I'm lost. I found the command line version of the tlbimp.exe but didn't have much success. I ran it on the vb COM dll (it was created such that type library is built in I'm told), and it created an "imported" version of the dll in the program files\common files\....1033\nt directory. When I tried viewing that type library it couldn't load it.
I don't see the option to do what you are saying VS.Net.
If you (or anybody) and just mention that a bit more, I'd appreciate it. I have to run now, but I'll check again 1st thing in am.
Thanks for all your help so far. 
There are only 10 types of people in this world....those that understand binary, and those that do not.
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You can't just use a COM control from .NET - a wrapper, or Runtime Callable Wrapper (RCW), has to be created first. This wrapper is in an COM interop assembly. You use tlbimp.exe to create a COM interop assembly and reference that assembly in your project. If you don't, you have to resort to many excrutiatingly painful methods of redefining interfaces and creating instances of COM objects at runtime and you don't get any marshaling or Type safety for free. You definitley DO NOT want to do it this way, and it's recommended that you don't.
For more information on creating interop assemblies, please read Exposing COM Components to the .NET Framework[^].
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According to that link (and another article I've found), when you add the COM reference to the project in VS.Net, it automatically converts it for you so that you are "on the same page".
Anyway....I found the assembly info you were talking about....I had to use a VS.Net command line tool called ildasm (which I didn't know about before).
But anyway...here it the info it generates:
<br />
.method public hidebysig newslot virtual <br />
instance string[] <br />
marshal( safearray bstr) <br />
MyFunction([in][out] string[]& marshal( safearray bstr) varNames) runtime managed internalcall<br />
{<br />
.custom instance void [mscorlib]System.Runtime.InteropServices.DispIdAttribute::.ctor(int32) = ( 01 00 15 00 03 60 00 00 )
.override COMInterface._COMClass::MyFunction <br />
}
I'm still trying to match the C# datatype for the argument for that VB6 COM function.
There are only 10 types of people in this world....those that understand binary, and those that do not.
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Yes, VS.NET does create the interop assembly but you never said you added such a COM reference and I've learned to assume nothing in this forum. After all, you did give the VB6 method signature and said you were trying to call it.
The data type (not C#, but .NET) is a String[] array, as well as is the return value, just as I mentioned previously. The param indeed takes a ref as designated by the address operator, &. More easily, however, would've been to look at the signature that IntelliSense returned, which would've shows the method signature as it is declared. It should look something like this:
string[] MyFunction(ref string[] varNames); When you call it, you must pass an initialized array:
string[] varNames = new string[] {"One", "Two" };
string[] retNames = obj.MyFunction(ref varNames);
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Heath Stewart wrote:
Yes, VS.NET does create the interop assembly but you never said you added such a COM reference and I've learned to assume nothing in this forum. After all, you did give the VB6 method signature and said you were trying to call it.
The data type (not C#, but .NET) is a String[] array, as well as is the return value, just as I mentioned previously. The param indeed takes a ref as designated by the address operator, &. More easily, however, would've been to look at the signature that IntelliSense returned, which would've shows the method signature as it is declared. It should look something like this:
Yes...you are right...sorry ".Net", not C#. 
Sorry I didn't mention the reference...this is my 1st time playing with COM and that is the only way I knew how to do it. So I just assumed that was assumed. If that makes sense.
Thanks for your answer, but if you go back to my original post, you'll see from my code examples that was exactly where I started. So...full circle?
There are only 10 types of people in this world....those that understand binary, and those that do not.
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I suppose we have. Is there any possibility you can send me the VB COM library? I don't need the source. If you have configured CodeProject to send email when someone replies to you, my email address will be above.
Microsoft MVP, Visual C#
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Thanks for the offer. It is sent.
There are only 10 types of people in this world....those that understand binary, and those that do not.
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Ok...I got it (what a pain)! I want to post the answer here for posterity in case somebody else has a similar problem in the future. For the record, I found the answer in a book a co-worker lent me (COM and .NET Interoperability by Andrew Troelsen).
The VB function signature:
<code>Public Function MyFunction(varNames() As String) As String() showed up as this in the assembly like this:
.method public hidebysig newslot virtual
instance string[]
marshal( safearray bstr)
MyFunction([in][out] string[]& marshal( safearray bstr) varNames) runtime managed internalcall
{
.custom instance void [mscorlib]System.Runtime.InteropServices.DispIdAttribute::.ctor(int32) = ( 01 00 15 00 03 60 00 00 )
.override COMInterface._COMClass::MyFunction
}
The problem was this assembly (and intellisense) was telling it it had to be a safearray and apparently it just wouldn't take a string[]! Not even if it was instantiated on initializaation like:
string[] varNames = new string[] {"One", "Two" };
The intellisense was telling me it had to be a "System.Array", not a string[]!
What needs to be done is not a "cast", but intantiating a System.Array and set it equal to the string array that was initialized and then pass in the ref to that array.
This was the way to get it working was:
COMInterface.COMObj oCOMObject = new COMInterface.COMObj();
string[] sNames = new string[] { "ProjectName" };
System.Array oTemp = sNames;
string[] sValues = new string[1];
System.Array oTempVals = sValues;
oTempVals = oCOMObject.TheCOMFunction( ref oTemp );
It wasn't intuitive....but now, in retrospect, it makes sense. Apparently you have to use the "System.Array" type for the "safearray" that it expects in the assembly, and since it doens't like you to cast it from string[] to System.Array, you have to just create an instance and set it equal.
There are only 10 types of people in this world....those that understand binary, and those that do not.
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Hi guys,
I have one user control implemented in .net (c#) and im trying to call it from a form in visual basic. the big problem is i cant add that control to vb designer, i just can add it as reference, so when the vb form comes up i cant see my control. i've done all the steps in this link (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dndotnet/html/callnetfrcom.asp).
does anybody any hint, thanx in advance.
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Make sure you have registered it correctly with regasm.exe /codebase, or set the project option in VS.NET to do so automatically. Also make sure that you DO NOT use AutoDispatch or AutoDual for your ClassInterfaceAttribute - ALWAYS declare your own class interface (implement as first interface) despite what Microsoft says in their docs. In fact, if you read more information about CCWs in other Microsoft documentation, they state as much, warning about using auto-generated interfaces. Always use a GuidAttribute as well, otherwise your VB project won't reference the right typelib next time you build your C# project.
Finally, I have noticed problems before when trying to add controls to VB6 with other work and articles I've done. First trying loading your control in the ActiveX Control Test Container (tstcon32.exe), which should be available from your VS.NET Tools menu if you installed the Platform SDK tools (installed by default). If it doesn't work in there, then you've done something wrong. Re-read the articles you linked or read Nick's at http://www.codeproject.com/dotnet/nettocom.asp[^]. Reply here if you're having problems.
If it does work, make sure you customize VB6's toolbox and add the .NET Control as an ActiveX control, not just a project reference.
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You wrote:
If it does work, make sure you customize VB6's toolbox and add the .NET Control as an ActiveX control, not just a project reference.
could u plz tell me how can i do this in vb?
(customize VB6's toolbox and add the .NET Control as an ActiveX control)
thanx alot
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Just right-click on in the toolbox and click "Components...". Find the assembly name (the value you put in the AssemblyTitleAttribute in AssemblyInfo.cs, or the assembly filename if you didn't put one), check it and click okay. If you don't see it, make sure you registered your assembly with regasm.exe /codebase "path/to/file.dll". This will register any COM-visible types, but you should declare your classes, interfaces, methods, properties, and enums appropriately. See Creating a CCW for COM enabled non .NET applications[^] for more information.
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hi guys, thanx for your great helps, but im still having problem.
I dont know why but i can insert my control in activex control test container in .net but i have to click implemented categories button then just select .net category.
but in visual basic or even in .net i just can see it as com reference not come component, i cann't add it to tool box!!!
i test this link but this one is the same too, it just shows in references not activex section.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cssample/html/vcsamCOMInteropPart2Sample.asp
any help really appreciated.
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COM registration - like almost everything else - is in the system registry. Even the categories are nothing more than GUIDs, so you can actually implement a catagory just by adding a GUID to your control's registration. Unfortunately, you can't do this through any attributes. All you could do is add a registration and unregistration method and use the ComRegisterFunctionAttribute and ComUnregisterFunctionAttribute on those methods.
If you just need this for your own development, there are two other things you can do. You can open the VBP project in a vanilla text editor like notepad.exe and add a new component (see the existing lines for examples), save it, then reload your VB project, or you can use regedit.exe to add the catagory like I mentioned above (this shouldn't become a common practice, though, since by implementing some catagories you imply that you support certain interfaces):- Click Start->Run
- Type "regedit" (without quotes) and click "OK"
- Expand HKEY_CLASS_ROOT\CLSID and find the GUID for your component (the class, not the interface, which you should'be attributed with the
GuidAttribute).
- Expand the GUID
- Expand "Implemented Catagories"
- Right-click on "Implemented Catagories" and select "New->Key"
- Type "{40FC6ED4-2438-11CF-A3DB-080036F12502}" (without quotes) and hit return.
- Restart VB and you should now see it.
Microsoft MVP, Visual C#
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guys I really appreciate your knowledge,
Im almost done with my component and i can test it in activex container test program and it works great, but i cant add this component to my vb project, i added this {40FC6ED4-2438-11CF-A3DB-080036F12502} for my class component guid in the registry as u told, but i cant still see it in there as com activex control, can u tell me what this {40FC6ED4-2438-11CF-A3DB-080036F12502} exactly does.
thanx alot
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That's the CATID (catagory ID) for the Controls (as in ActiveX controls) catagory. Use oleview.exe to view these different catagories. This tool is also available by default from the VS.NET Tools menu as the "OLE/COM Object Viewer".
Since I can't really see your machine to know if everything is setup correctly, you could always try what I mentioned before: open the .vbp project file in notepad.exe (or some other vanilla text editor) and add the line manually, so it would look something like this:
Object={YOUR CLASS GUID}#MajorVersion.MinorVersion#0; Filename.dllIt should then appear in the toolbox.
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it wroks and thanx very alot.
I was wondering if you say me what can do to make this control visible for all of component client container, sometimes i need to use this control in vb, vc,delphi,... , what i have to do to make it like the other activex control which commin up when you open the component reference form in the vb or anyother language.
and another isues is one i've created one tlb file from that component, but now i cant remove it, i closed every thing, do i need to unregister it,,how !!!
thanx very much
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As I mentioned a while back, you can implement static methods that are attributed with ComRegisterFunctionAttribute and ComUnregisterFunctionAttribute that use the Microsoft.Win32.RegistryKey to do this manually. These functions are called in addition to normal registration of the class.
If you can't release the typelib (.tlb file), you need to remove ALL references to objects defined by the typelib in your project and remove the control from the toolbox.
If you have questions about how COM objects in the VB6 IDE, please jump over to the VB forum.
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I just went through this last week (here at work).
Here is the MSDN article that gave me the proper example I needed.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/csref/html/vcwlkcominteroppart2cservertutorial.asp
You must generate the GUIDs with regasm like Heath mentioned. From VS go to Tools menu and select "Create GUID".
There are only 10 types of people in this world....those that understand binary, and those that do not.
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