DLLs in C#, legacy code concerns

[Andrew S. Giles]

OK, I just want to make sure I am correct in the following statements, and
then to get some advice as to how I should proceed.

First, is it accurate to say that in order for C# to use a DLL, the classes
and members exposed must utilize a COM interface?

I tried adding a refernce to a DLL that was just created (in C++ to cross
compile between Microsoft Visual C++ 6.0 and Borland C++ Builder 5, providing
messaging functionality through ACE) to solve a communications problem
between Borland and Microsoft compilers, only to have Visual Studio .NET 2003
(version 7.1 I believe) tell me that I cannot add the DLL file because it is
neither a valid assembly, nor a COM object.

Is is possible to use this DLL in Visual Studio .NET 2003 if I write my user
interface and export routines in C++ instead of C#?

How would you suggest I gain access to the messaging functionality located
in this DLL for my application?

Thanks in advance for all the help,

Andrew S. Giles

[Nicholas Paldino [.NET/C# MVP]]

Andrew,

Basically, if you want to interop with unmanaged code, you have two
choices. The first would be to expose it through a COM object, the second
is to export functions from a DLL. You could also create a managed wrapper
in C++ if you wish, and then set your reference to that.

Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Andrew S. Giles" <An**********@discussions.microsoft.com> wrote in message
news:CE**********************************@microsof t.com...

OK, I just want to make sure I am correct in the following statements, and
then to get some advice as to how I should proceed.

First, is it accurate to say that in order for C# to use a DLL, the
classes
and members exposed must utilize a COM interface?

I tried adding a refernce to a DLL that was just created (in C++ to cross
compile between Microsoft Visual C++ 6.0 and Borland C++ Builder 5,
providing
messaging functionality through ACE) to solve a communications problem
between Borland and Microsoft compilers, only to have Visual Studio .NET
2003
(version 7.1 I believe) tell me that I cannot add the DLL file because it
is
neither a valid assembly, nor a COM object.

Is is possible to use this DLL in Visual Studio .NET 2003 if I write my
user
interface and export routines in C++ instead of C#?

How would you suggest I gain access to the messaging functionality located
in this DLL for my application?

Thanks in advance for all the help,

Andrew S. Giles

[BenW]

You can access non COM dlls lookup extern keyword and DllImport attribute.
BenW

"Andrew S. Giles" wrote:

OK, I just want to make sure I am correct in the following statements, and
then to get some advice as to how I should proceed.

First, is it accurate to say that in order for C# to use a DLL, the classes
and members exposed must utilize a COM interface?

I tried adding a refernce to a DLL that was just created (in C++ to cross
compile between Microsoft Visual C++ 6.0 and Borland C++ Builder 5, providing
messaging functionality through ACE) to solve a communications problem
between Borland and Microsoft compilers, only to have Visual Studio .NET 2003
(version 7.1 I believe) tell me that I cannot add the DLL file because it is
neither a valid assembly, nor a COM object.

Is is possible to use this DLL in Visual Studio .NET 2003 if I write my user
interface and export routines in C++ instead of C#?

How would you suggest I gain access to the messaging functionality located
in this DLL for my application?

Thanks in advance for all the help,

Andrew S. Giles

[Andrew S. Giles]

ok, I am trying to get this to work, and wonder if I have messed something up.

The DLL contains a public class that I will call Fred.

So, I write the following in C#:
[DllImport("vpcmsgmfcd.dll")]
public static extern Fred classFred;

and I get an error asking what namespace am I supposed to be using.

I know I am doing something wrong, but I just do not know what. I am sorry
to be asking these annoyingly simple questions, but any help would be greatly
appreciated.

Andrew

"BenW" wrote:

You can access non COM dlls lookup extern keyword and DllImport attribute.
BenW

"Andrew S. Giles" wrote:

OK, I just want to make sure I am correct in the following statements, and
then to get some advice as to how I should proceed.

First, is it accurate to say that in order for C# to use a DLL, the classes
and members exposed must utilize a COM interface?

I tried adding a refernce to a DLL that was just created (in C++ to cross
compile between Microsoft Visual C++ 6.0 and Borland C++ Builder 5, providing
messaging functionality through ACE) to solve a communications problem
between Borland and Microsoft compilers, only to have Visual Studio .NET 2003
(version 7.1 I believe) tell me that I cannot add the DLL file because it is
neither a valid assembly, nor a COM object.

Is is possible to use this DLL in Visual Studio .NET 2003 if I write my user
interface and export routines in C++ instead of C#?

How would you suggest I gain access to the messaging functionality located
in this DLL for my application?

Thanks in advance for all the help,

Andrew S. Giles

[Nicholas Paldino [.NET/C# MVP]]

Andrew,

If you want to export a class, then you have to wrap it in a manged
wrapper in C++, or you have to use COM interop. Using the DllImport
attribute works only for functions exported from the dll, not for classes.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Andrew S. Giles" <An**********@discussions.microsoft.com> wrote in message
news:D1**********************************@microsof t.com...

ok, I am trying to get this to work, and wonder if I have messed something
up.

The DLL contains a public class that I will call Fred.

So, I write the following in C#:
[DllImport("vpcmsgmfcd.dll")]
public static extern Fred classFred;

and I get an error asking what namespace am I supposed to be using.

I know I am doing something wrong, but I just do not know what. I am
sorry
to be asking these annoyingly simple questions, but any help would be
greatly
appreciated.

Andrew

"BenW" wrote:

You can access non COM dlls lookup extern keyword and DllImport
attribute.
BenW

"Andrew S. Giles" wrote:

> OK, I just want to make sure I am correct in the following statements,
> and
> then to get some advice as to how I should proceed.
>
> First, is it accurate to say that in order for C# to use a DLL, the
> classes
> and members exposed must utilize a COM interface?
>
> I tried adding a refernce to a DLL that was just created (in C++ to
> cross
> compile between Microsoft Visual C++ 6.0 and Borland C++ Builder 5,
> providing
> messaging functionality through ACE) to solve a communications problem
> between Borland and Microsoft compilers, only to have Visual Studio
> .NET 2003
> (version 7.1 I believe) tell me that I cannot add the DLL file because
> it is
> neither a valid assembly, nor a COM object.
>
> Is is possible to use this DLL in Visual Studio .NET 2003 if I write my
> user
> interface and export routines in C++ instead of C#?
>
> How would you suggest I gain access to the messaging functionality
> located
> in this DLL for my application?
>
> Thanks in advance for all the help,
>
> Andrew S. Giles

[Andrew S. Giles]

I can only export functions, but not classes, is this correct?

Andrew

"Nicholas Paldino [.NET/C# MVP]" wrote:

Andrew,

Basically, if you want to interop with unmanaged code, you have two
choices. The first would be to expose it through a COM object, the second
is to export functions from a DLL. You could also create a managed wrapper
in C++ if you wish, and then set your reference to that.

Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Andrew S. Giles" <An**********@discussions.microsoft.com> wrote in message
news:CE**********************************@microsof t.com...

OK, I just want to make sure I am correct in the following statements, and
then to get some advice as to how I should proceed.

First, is it accurate to say that in order for C# to use a DLL, the
classes
and members exposed must utilize a COM interface?

I tried adding a refernce to a DLL that was just created (in C++ to cross
compile between Microsoft Visual C++ 6.0 and Borland C++ Builder 5,
providing
messaging functionality through ACE) to solve a communications problem
between Borland and Microsoft compilers, only to have Visual Studio .NET
2003
(version 7.1 I believe) tell me that I cannot add the DLL file because it
is
neither a valid assembly, nor a COM object.

Is is possible to use this DLL in Visual Studio .NET 2003 if I write my
user
interface and export routines in C++ instead of C#?

How would you suggest I gain access to the messaging functionality located
in this DLL for my application?

Thanks in advance for all the help,

Andrew S. Giles

[jeff_louie]

Andrew... Also, if you write it in ATL COM, all you do is add a reference to the dll and Visual Studio
creates the managed wrapper class for you.

http://www.geocities.com/jeff_louie/...op/atl_com.htm

How would you suggest I gain access to the messaging functionality located

in this DLL for my application?<

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