I have a header-file, the COM interface. I have created a small win32 program which works, but my main program is written in C#.
So I would like to import this COM object in my main program, but how do I do this, when the only thing I got is the header-file?
All places I've looked I need a tlb-file..?
I'm new to COM objects so just ask if you need some extra info, or have another workaround :)
[UPDATE]
First thanks for all the responses!
I've tried some different things, but haven't solved my issue yet. In my research, I've found an article describing COM Interop http://msdn.microsoft.com/en-us/library/aa645736(v=vs.71).aspx#vcwlkcominteroppart1cclienttutorialanchor2
This haven't helped me out. But I've found that I should be able to get moving if I can complete the following:
Declaring a COM coclass:
[ComImport, Guid("7C075F7F-FD71-40a2-AC63-0D0C4DB39ECA")]
class CCamera
{
// Cannot have any members here
// NOTE that the C# compiler will add a default constructor
// for you (no parameters).
}
Creating a COM class wrapper:
[Guid("AD87369B-3BBA-4f1c-81C5-B92FCEA9A1F4"),
InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
interface ICamera
{
//static HRESULT GetCameraInterface();
bool StartPreview();
bool StopPreview();
}
Using Casts Instead of QueryInterface:
try
{
CCamera cam = new CCamera();
ICamera test = (ICamera)cam;
//test.StartPreview();
}
catch (Exception e)
{
Console.WriteLine(e.StackTrace);
}
I get an invalid cast exception, so is this because I miss implementing some methods in the interface?
And how do I implement the following method from the c++ interface:
static HRESULT GetCameraInterface(void __RPC_FAR *__RPC_FAR *ppvObject);
[SOLUTION]
OK I got a solution, but I never solved to wrap the interface.
Instead I created a C++ dll project and exposed the methods I needed. Then in my C# project, could I use these methods with DllImport. If anybody need more explanation on how I archived this, send me a message.
If it is registered as a COM-Object, then you can import it via the Add Reference Dialog. Right click on the project --> Add Reference. Then select the Tab "COM" and you can select your COM Interface. Required Interop classes for .NET will be generated automatically.
you need to register the COM dll with the following line
regasm COMDll.DLL /tlb
then you can add it as a reference to your project.
I have completed some research and found that you can include a header file in an idl file in much the same way you do with C, below are the two links that show you how to include the header file in the idl and compile the idl to a tbl file which you can use in .Net:
http://msdn.microsoft.com/en-us/library/windows/desktop/aa367049(v=vs.85).aspx
http://msdn.microsoft.com/en-us/library/windows/desktop/aa367064(v=vs.85).aspx
I haven’t tried it and it looks like you may encounter some difficulty if the header file contains more than just the COM definitions, so good luck and please let me know how it went.
Related
First, I realize that there are many posts here that discuss this topic. I must have read 20+ of them, easily. But none of them give the answer that I seek.
I have written a tiny C# test COM DLL with a single method in it that prints "I am alive!" in a message box. Using VStudio as admin, I can build and register the COM object. I have successfully called the object from VBA and run the method. And I can see the name of the COM Interface in the VStudio Add Reference / COM dialog box. This all makes me think the object is properly constructed, registered, and usable.
Now I'm trying to call it from a console C# app. Like many others, I'm trying to figure out the equivalent of the VBA "CreateObject("DLLName.ClassName")" code to get hold of the object in C#.
One way is to just add a reference to the DLL to my console app project. I point to the assembly through the Projects section of the Add Reference dialog, not through the COM section of the dialog. Then I can simply say var o = new MyComImplementationClass(); and treat it like any other class. That works, but it means my console app is cheating and not using the COM object through the usual COM GAC interface.
Another way (that doesn't work, but I wish it did), is to add the reference through the COM tab on the Add Reference dialog. I can see it but VS protests that "the XXX.tlb file was exported from a .NET assembly. Add a reference to the assembly instead." Which brings me back to the solution above, which I think means that my app is cheating. (I didn't have to add references to my VBA test app, for example.)
Another way is to use Type.GetTypeFromProgId as shown by this code fragment below. But I can't get that to work either. I must be passing in the incorrect ProgID string - I get the sense it has something to do with registry info and is not the same "DLLName.ClassName" string that I feed CreateObject() in VBA.
public static dynamic ComObjectGet () {
const string progID = "ComExampleDLLName.ComImplementationClassName";
Type foo = Type.GetTypeFromProgID (progID);
dynamic COMobject = Activator.CreateInstance (foo);
return COMobject;
}
Worse yet, on this MSDN example page it says "This method is provided for COM support. Program IDs are not used in Microsoft .NET Framework because they have been superseded by the concept of namespace." So probably I should not be using the GetTypeFromProgID at all.
If it helps any, I can use VSTO in C# to call the MSOffice primary interop assemblies. But they load from the COM tab of the add reference dialogs (which is where I want my COM library to load from).
For clarity, my COM DLL name is ComExampleLibrary.dll. The default namespace is ComExampleNamespace. The interface name is IComInterface, and the implementation classname is ComImplementation. The internal method name is Run.
Could someone give me instructions or a code snippet that does the "right, approved" thing for calling COM objects (not just the ones I write) from C#? Thank you.
Thanks to the people who helped me out, here is the answer. Both GetTypeFromProgID and GetTypeFromCLSID work as shown below. My problem was that I was using "AssemblyName.ClassName" instead of "Namespace.ClassName" in the call to GetTypeFromProgID.
public static dynamic ComObjectGet () {
const string progID = "ComExampleNamespace.ComImplementation";
Type foo = Type.GetTypeFromProgID (progID);
//var bar = Guid.Parse ("99929AA7-0334-4B2D-AC74-5E282A12D06C");
//Type foo = Type.GetTypeFromCLSID (bar);
dynamic COMobject = Activator.CreateInstance (foo);
return COMobject;
}
So my original code was correct, but I was passing in the wrong argument. This snippet is the equivalent of the VBA CreateObject("Namespace.ClassName") call.
I still don't know why I cannot add a reference to the COM item in the COM tab of the Add Reference dialog like I would for any other COM object. I suppose that's a different question.
I have an unmanaged DLL which I'm currently calling from C# using a COM Class Wrapper.
[ComImport(), Guid("75E81043-CAD5-11D3-800D-00105A5E2FA0")]
public class MyObject { }
[ComImport(), Guid("75E81042-CAD5-11D3-800D-00105A5E2FA0"),
InterfaceType(ComInterfaceType.InterfaceIsDual)]
public interface MyInterface
{
string EncryptString([In, MarshalAs(UnmanagedType.BStr)] string bstrOrginal);
}
Then to call:
MyInterface obj = (MyInterface)new MyObject();
string crypt = obj.EncryptString("something");
This works, the return value is as I expect. However, it requires that the dll is registered with regsvr32.
I'm looking for a way to do this without the requirement of needing to regsvr32. Preferably, by just having a copy of the dll available. It is worth noting, I have the source for the unmanaged dll, and the ability to modify it if necessary.
A shove in the right direction would be greatly appreciated.
I have wanted to do the same thing myself. As Jim mentions it is possible to get the address of DllRegisterServer and call it, but that still modifies your registry with the various entries. If you don't want to do this (for example, you might not have the necessary privileges to write to the Registry), then there is another way.
Any DLL that houses one or more in-process COM objects must expose the DllGetClassObject function. This function is used to acquire an instance of the COM class factory that is used to create a COM object. What you need to do is:
Load the library (DLL) that houses the desired COM object
Locate the DllGetClassObject function
Call DllGetClassObject, passing it the CLSID of the desired COM object, this will return an IClassFactory instance.
Call the CreateInstance method on the class factory to get an instance of the COM object.
Cast the returned object to the interface you wish to use.
Note that there be dragons with this approach -- it is fairly low level. If you get anything wrong you will experience access violation exceptions or worse. (For instance, your interface declaration has to exactly match the COM interface).
I have included some sample code at gist which you might like to use if you want to go this way.
Using this code would look something like this:
// Load the library. You dispose this after you are finished with
// all of your COM objects.
var library = new LibraryModule();
library.Load("mylibrary.dll"); or whatever your dll is called
var clsid = new Guid("75E81043-CAD5-11D3-800D-00105A5E2FA0");
var myObject = (MyInterface)ComHelper.CreateInstance(library, clsid);
Just note that if you dispose of the LibraryModule object, then this will unload the DLL. Depending on your needs, you might just assign the value to a static field so that it exists for the lifetime of the program.
You need to set up your unmanaged DLL for registration-free COM. There's a pretty complete walkthrough here, with plenty of examples. Among other things, it involves using manifests to point to the file, side-by-side assemblies, and some interop.
An important note in the walkthrough is that registration is required for the initial setup of the client, but not later.
If your DLL has to be a COM object, then it must be registered. This registration does not need to be performed by regsvr32. All regsvr32 does is load the DLL, get the address of DllRegisterServer and call it it. DllRegisterServer adds the necessary entries to the registry for an application to use the object.
If your DLL does not need to be a COM object, you can modify it to simply export the function(s) you need and p-invoke it(them).
I have declared a COM visible class in C#. The code is as follows:
[ComVisible(true)]
public class AComVisibleClass : TheParentClass
{
public bool SomeFunc(string id)
{
return true;
}
}
This class is instantiated by a factory class, also COM accessible.
But if I try to access in a VB script file, a DISP_E_UNKNOWNNAME exception is thrown.
This is a new class on a pre-existent library we have here at work. All other classes are accessible through COM. The whole library is compiled into a single assembly file. I have registered the new assembly using regasm, but I still get this exception.
I've tried to debug the COM call using VS2008. The factory class seems to be able to instantiate the AComVisibleClass. The aforementioned exception is thrown only when the factory tries to execute SomeFunc.
I know this may sound a little(?) bit vague, but I cannot expose the real code here. If someone need more information, please ask me.
I can think of three possible reasons for this problem:
Reason 1: Wrong name used in CreateObject:
I suppose that your VBScript code calls
something like
this:
Set obj = CreateObject("MyLibrary.AComVisibleClass")
If this is correct, then please open the registry editor and check whether the HKEY_CLASSES_ROOT key contains a subkey called MyLibrary.AComVisibleClass.
If it does not, then your library name possibly is different than you expected. Search the registry for AComVisibleClass to find the correct library name.
Reason 2: 64-bit issues:
If the problem happens on a 64-bit operating system, the reason could be that your VBScript runs as a 32-bit process and the C# COM DLL is 64-bit or vice versa.
Reason 3: Wrong function name:
You might be using the wrong function name in the script, e.g. obj.SomeFnc(1) instead of obj.SomeFunc(1), or the function name you have chosen is a reserved keyword in VBScript or it contains unusual characters.
Sounds like you need to support IDispatch.
Check out Does C# .NET support IDispatch late binding?
edit
This answer is likely wrong, and I may yet wind up deleting it. For now, it seems to add value, so I'll let it stay.
I need to use a COM component (a dll) developed in Delphi ages ago. The problem is: the dll does not contain a type library... and every interop feature (eg. TlbImp) in .NET seem to rely on TLBs. The component has been used in Delphi programs here for many years without problems because "It's not much of a problem using COM objects from Delphi, because we know the interfaces" (quote Delphi developer).
Is there any way I can use this DLL from c# without a TLB? I've tried using the DLL as unmanaged, but the only method it exports are DllUnregisterServer, DllRegisterServer, DllCanUnloadNow and DllGetClassObject. I know the names of the classes and functions I'm going to use, if that can be of any help.
UPDATE:
I've tried implementing Jeff's suggestion, but I'm getting this error:
"Unable to cast COM object of type 'ComTest.ResSrvDll' to interface type 'ComTest.IResSrvDll'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{75400500-939F-11D4-9E44-0050040CE72C}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE))."
This is what I've done:
I got this interface definition from one of the Delphi-guys:
unit ResSrvDllIf;
interface
type
IResSrvDll = interface
['{75400500-939F-11D4-9E44-0050040CE72C}']
procedure clearAll;
function ResObjOpen(const aClientID: WideString; const aClientSubID: WideString;
const aResFileName: WideString; aResShared: Integer): Integer; {safecall;}
...
end;
implementation
end.
From this I've made this interface
using System.Runtime.InteropServices;
namespace ComTest
{
[ComImport]
[Guid("75400500-939F-11D4-9E44-0050040CE72C")]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IResSrvDll
{
int ResObjOpen(string aClientID, string aClientSubID, string aResFileName, int aResShared);
}
}
And this coclass (got the guid from the delphi-guys)
using System.Runtime.InteropServices;
namespace ComTest
{
[ComImport]
[Guid("75400503-939F-11D4-9E44-0050040CE72C")]
public class ResSrvDll
{
}
}
UPDATE
The solution from Jeff is the way to do it. It is worth noticing, though, that the interface definition must match the COM-components exactly! ie. same order, same names, etc.
You just need the CLS_ID and interface id. I wrote about this specific issue on my blog:
"Using Obscure Windows COM APIs in .NET"
Write a wrapper in VB.Net. VB.Net supports true late binding (no messy reflection). All you need is the progId. You should also implement IDisposable to explicitely manage the component lifecycle.
It is quite frequent that you will encounter an interface implementation that is not backed by a type library (Delphi or otherwise). Shell extensions are one example.
You basically need to make a Windows API call to create the instance through the proper COM function calls. The API will take care of managing the DLL via the exported functions you mentioned earlier.
You will need to recreate the interface definition in C# code but after that you simply create the object, cast it to the interface, and it is no different than anything else. The only real caveat here is, depending on your usage, you may have some threading issues to deal with so check the "threading model" that was used for the DLL and consider your usage based on that.
Here is a link to a tutorial on consuming the interfaces that are not TLB based.
Tutorial
If you've managed to create an instance of the object, you're over the first major hurdle!
Now try this:
myObject.GetType().InvokeMember(
"ResObjOpen", // method name goes here
BindingFlags.InvokeMethod,
null,
myObject,
new object[] {
someClientID, // arguments go here
someSubId,
somFileName,
someInt} );
The reason I think you may need to do this is if the Delphi COM object is not a "dual" object. It may only support late binding, i.e. the kind of invocation you see above.
(In C# 4.0 they're making this easier with the dynamic keyword.)
EDIT: Just noticed something very suspicious. The IID for the interface and the CLSID for the object itself appear to be the same. That's not right.
Given that you've succeeded in creating the object, it would appear to be the CLSID of the object. So it's not the right IID. You need to go back to your Delphi folks and ask them to tell you what the IID of the interface IResSrvDll is.
Edit again: You could try changing the enum member you specify from ComInterfaceType. There should be ones for IDispatch and "dual" - although as your object doesn't support IDispatch, neither of those should be the right choice. The IUnknown setting (which appears in your sample code) should work - suggesting that the IID is wrong.
Yes and no.
All C# (and any CLR language) needs in order communicate with a COM object is a compatible interface signature. Typically specifying the methods, GUID and apartment style of the interface. If you can add this definition into your code base then the TLB is not necessary.
There is a small caveat that comes with that statement. I believe you will get into trouble if you try and use a COM object across apartment boundaries and don't have a suitable TLB registered. I can't 100% remember on this point though.
You can also do late binding and then invoke methods through reflection (myObject.InvokeMember("NameOfTheMethod", options, params, etc.)).
A wrapper should, however, offer better performance and faster marshalling.
I suspect that the dynamic keyword (C# 4.0) will accomplish this. If it does, it will give results which are largely equivalent to invoking the methods, i.e. how Groo suggests.
I've been told to write a dialog in C# which must be instantiated from an unmanaged c++ dll. We do this in other places in our code by simply adding a managed c++ class to the C++ project, then calling the C# dll from the managed c++ class. However I'm finding that doesn't work for me from where I have to do it. I think because the c++ dll is an MFCActiveX project. As soon as i set the clr on any file in this project, it will no longer register correctly. When i attempt to register it, i get three errors, then a message that it registered. However when i try to use it i get a 0x80040111 "ClassFactory cannot supply requested class" error.
If anyone has any idea what the problem is here i would greatly appreciate it. I either need to be able to accomplish this (preferred) or prove that it's not possible.
Thanks
I can't see how a MFCActiveX project would prevent you from creating the C# class in this way. Unless it simply does not allow for a managed class to be added.
If you can't get the managed C++ class trick to work, another option is to use COM. It's possible to register a factory of sorts in the C# project as a COM object. Say give it the following interface
[ComVisible(true)]
[Guid("babe87fc-1467-4913-a1d3-47eeedf1afb5")]
public interface IDialogFactory {
void Create();
}
You'd also have to create a backing class as well. But then you could register the managed assembly and use COM to access it.
You must now register it with "regasm" instead of "regsvr32".