You
can
export
your .NET class for use with
existing
COM components, although this is an
unusual requirement. The
Regasm
tool will register the metadata
from your component in the system registry.
You invoke Regasm
with the name of the DLL. For
example:
Regasm myAssembly.dll
This will export your component’s metadata to the Registry. For example, you can create a new C# DLL project in which you re-create your four-function calculator, as shown in Example 22-8.
Example 22-8. The four-function calculator in a DLL
using System; namespace Programming_CSharp { public class Calculator { public Calculator( ) { } public Double Add (Double left, Double right) { return left + right; } public Double Subtract (Double left, Double right) { return left - right; } public Double Multiply (Double left, Double right) { return left * right; } public Double Divide (Double left, Double right) { return left / right; } } }
You save this to a file named Calculator.cs
in a
project named ProgrammingCSharpDLL
. After building
this project, you can register it with:
Regasm ProgrammingCSharpDLL.dll
A quick check of the Registry shows that a PROGID was created for the DLL, as shown in Figure 22-18.
You can now invoke the four-function calculator as a COM object using standard VBScript. For example, you can create a tiny Windows Script Host file, as shown in Example 22-9.
Example 22-9. Invoking the Calculator COM object with a Windows scripting host file
dim calc dim msg dim result set calc = CreateObject("ProgrammingCSharpDLL.Calculator") result = calc.Multiply(7,3) msg = "7 * 3 =" & result & "." Call MsgBox(msg)
When this is run, a dialog box pops up to verify that the object was created and invoked, as shown in Figure 22-19.
If
you wish
to use early binding with your .NET DLL you will need to create a
type library. You can do so with the TlbExp
(Type
Library Export) utility, by writing:
TlbExp ProgrammingCSharpDLL.dll /out:Calc.tlb
The result is a type lib that you can browse for and view in the OLE/COM object viewer within Visual Studio, as shown in Figure 22-20.
With this type library in hand, you can import the calculator class into any COM environment.
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