What exactly does the VS project option "Register for COM interop" actually do? Because when I build my library with this option enabled I can call CreateObject on my library from VBScript. But if I build without this and then run regasm manually CreateObject fails. So I'm wondering — what does VS2010 do that I'm not doing?
Visual-studio – What does “Register for COM Interop” actually do
com-interopvisual studiovisual studio 2010
Related Solutions
C# language version history:
These are the versions of C# known about at the time of this writing:
- C# 1.0 released with .NET 1.0 and VS2002 (January 2002)
- C# 1.2 (bizarrely enough); released with .NET 1.1 and VS2003 (April 2003). First version to call
Dispose
onIEnumerator
s which implementedIDisposable
. A few other small features. - C# 2.0 released with .NET 2.0 and VS2005 (November 2005). Major new features: generics, anonymous methods, nullable types, and iterator blocks
- C# 3.0 released with .NET 3.5 and VS2008 (November 2007). Major new features: lambda expressions, extension methods, expression trees, anonymous types, implicit typing (
var
), and query expressions - C# 4.0 released with .NET 4 and VS2010 (April 2010). Major new features: late binding (
dynamic
), delegate and interface generic variance, more COM support, named arguments, tuple data type and optional parameters - C# 5.0 released with .NET 4.5 and VS2012 (August 2012). Major features: async programming, and caller info attributes. Breaking change: loop variable closure.
- C# 6.0 released with .NET 4.6 and VS2015 (July 2015). Implemented by Roslyn. Features: initializers for automatically implemented properties, using directives to import static members, exception filters, element initializers,
await
incatch
andfinally
, extensionAdd
methods in collection initializers. - C# 7.0 released with .NET 4.7 and VS2017 (March 2017). Major new features: tuples, ref locals and ref return, pattern matching (including pattern-based switch statements), inline
out
parameter declarations, local functions, binary literals, digit separators, and arbitrary async returns. - C# 7.1 released with VS2017 v15.3 (August 2017). New features: async main, tuple member name inference, default expression, and pattern matching with generics.
- C# 7.2 released with VS2017 v15.5 (November 2017). New features: private protected access modifier, Span<T>, aka interior pointer, aka stackonly struct, and everything else.
- C# 7.3 released with VS2017 v15.7 (May 2018). New features: enum, delegate and
unmanaged
generic type constraints.ref
reassignment. Unsafe improvements:stackalloc
initialization, unpinned indexedfixed
buffers, customfixed
statements. Improved overloading resolution. Expression variables in initializers and queries.==
and!=
defined for tuples. Auto-properties' backing fields can now be targeted by attributes. - C# 8.0 released with .NET Core 3.0 and VS2019 v16.3 (September 2019). Major new features: nullable reference-types, asynchronous streams, indices and ranges, readonly members, using declarations, default interface methods, static local functions, and enhancement of interpolated verbatim strings.
- C# 9.0 released with .NET 5.0 and VS2019 v16.8 (November 2020). Major new features: init-only properties, records, with-expressions, data classes, positional records, top-level programs, improved pattern matching (simple type patterns, relational patterns, logical patterns), improved target typing (target-type
new
expressions, target typed??
and?
), and covariant returns. Minor features: relax ordering ofref
andpartial
modifiers, parameter null checking, lambda discard parameters, nativeint
s, attributes on local functions, function pointers, static lambdas, extensionGetEnumerator
, module initializers, and extending partial.
In response to the OP's question:
What are the correct version numbers for C#? What came out when? Why can't I find any answers about C# 3.5?
There is no such thing as C# 3.5 - the cause of confusion here is that the C# 3.0 is present in .NET 3.5. The language and framework are versioned independently, however - as is the CLR, which is at version 2.0 for .NET 2.0 through 3.5, .NET 4 introducing CLR 4.0, service packs notwithstanding. The CLR in .NET 4.5 has various improvements, but the versioning is unclear: in some places it may be referred to as CLR 4.5 (this MSDN page used to refer to it that way, for example), but the Environment.Version
property still reports 4.0.xxx.
As of May 3, 2017, the C# Language Team created a history of C# versions and features on their GitHub repository: Features Added in C# Language Versions. There is also a page that tracks upcoming and recently implemented language features.
I created a class library project based on your code as follows:
In the project properties page, select the Signing tab. Check the 'Sign the assembly' checkbox and select <New...>
from the 'Choose a strong name key file:' drop down box.
I then added the following class (Example.cs)
:
[Guid("77699130-7D58-4d29-BE18-385871B000D1")]
[InterfaceType(ComInterfaceType.InterfaceIsDual)]
[ComVisible(true)]
public interface IExample
{
[DispId(1)]
string GetText();
[DispId(2)]
void SetText(string text);
}
[Guid("F91E5EE1-D220-43b5-90D1-A48E81C478B7")]
[ClassInterface(ClassInterfaceType.None)]
[ComVisible(true)]
public class Example : IExample
{
private string m_text = "default text";
[ComVisible(true)]
public string GetText()
{
return m_text;
}
[ComVisible(true)]
public void SetText(string text)
{
m_text = text;
}
}
I then built the project then dropped to a command line where the DLL was output from the build.
To register:
regasm.exe COMInteropTesting.dll /register /codebase /tlb
If your component needs to be accessible to multiple applications:
gacutil.exe -i COMInteropTesting.dll
This all worked fine on Windows 2003 32bit, Windows 2008 32bit and Windows 7 64 bit.
One gotcha though is that if you're testing the component with say CScript on a 64 bit system, you need to run the correct CScript interpreter. If you registered the assembly using 32bit RegAsm.exe
(at C:\Windows\Microsoft.NET\Framework\v2.0.50727
) then you need to run the 32 bit CScript interpreter at c:\Windows\SysWOW64
.
Best Answer
It does the same thing as running Regasm.exe with the /tlb and /codebase options. The /codebase option is probably the one you forgot. Regasm likes assuming you put the DLL in the GAC and generates a warning when you don't. The GAC is indeed a very good way to avoid DLL Hell, always a COM problem. But not appropriate on your dev machine, you don't want to pollute the GAC while developing and testing the code. It only matters on your user's machine, the one that's likely to be exposed to multiple versions.
Using the wrong version of Regasm.exe on a 64-bit machine is another way to get in trouble, there are usually 4 versions on your machine. Be sure to distinguish the 32-bit and 64-bit versions (c:\windows\microsoft\framework vs framework64), they write different registry keys. You want to pick the one that's compatible with the client app. Using both is okay too, .NET code can run in either mode, but pretty unusual. And distinguish between the v2.0.50727 (.NET 2.0 through 3.5SP1) and the v4.0 versions. Picking the right Visual Studio Command Prompt is half the battle.