Importing COM Components
Many of the COM components that companies develop are not ActiveX Controls; they are standard COM dynamic link library (DLL ) files . To see how to use these with .NET, return to VB6 and create a COM business object that will act exactly as the component from the previous section did.
Tip
Once again, if you don't have VB6, you can download the DLL as explained earlier.
The first step is to create a new ActiveX DLL project. This is how VB6 creates standard COM DLLs. Name the class ComCalc
and name the project ComCalculator
. Save the file and project. Copy the methods from Example 7-1 (shown here for your convenience in Example 7-3) into the code window.
Example 7-3. Methods for VB6 COM DLL ComCalc
Public Function _ Add(left As Double, right As Double) _ As Double Add = left + right End Function Public Function _ Subtract(left As Double, right As Double) _ As Double Subtract = left - right End Function Public Function _ Multiply(left As Double, right As Double) _ As Double Multiply = left * right End Function Public Function _ Divide(left As Double, right As Double) _ As Double Divide = left / right End Function
Integrating the COM DLL into .NET
Create a new form called frmCOMDLL
. Add a menu choice to the Fun menu on the Welcome form that invokes that form.
Now that you have created the ComCalc
DLL, you can import it into .NET. Before you can import it, however, you must choose between early and late binding. When the client calls a method on the server, the address ...
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