Using COM Components

Launch Visual Basic 6. Create a new ActiveX DLL project.

Select the Project1 node in the Project Explorer window and rename it MyCustomer.

Select the Class1 node in the Project Explorer window and rename it Balances.

Add this code to the Balances class:

Option Explicit



Private mintCustomerCount As Integer

Private macurBalances(1 To 10) As Currency



' Create a read-only CustomerCount property

Public Property Get CustomerCount() As Integer

    CustomerCount = mintCustomerCount

End Property



' Create a GetBalance method

Public Function GetBalance( _

   CustomerNumber As Integer) As Currency

    GetBalance = macurBalances(CustomerNumber)

End Function



' Initialize the data

Private Sub Class_Initialize()

    Dim intI As Integer

    mintCustomerCount = 10



    For intI = 1 To 10

        macurBalances(intI) = _

          Int(Rnd(1) * 100000) / 100

    Next intI

End Sub

Save the Visual Basic project.

Select File, Make MyCustomer.dll to create the COM component.

Launch a .NET command prompt by selecting Start, Programs, Microsoft Visual Studio .NET, Visual Studio .NET Tools, Visual Studio .NET Command Prompt.

Inside the command prompt window, navigate to the folder that contains the MyCustomer.dll COM library.

Enter this command line to run the Type Library Importer tool:

tlbimp MyCustomer.dll /out:NETMyCustomer.dll

Launch Visual Studio .NET. Create an ASP.NET Web service application named 320C08.

Right-click the References node in Solution Explorer and select Add Reference.

Click the Browse button in the Add Reference dialog box. Browse to the NETMyCustomer.dll file that you created in step 3. Click OK to add the reference to the project.

Right-click the Service1.asmx file in Solution Explorer and rename it StepByStep8_2.asmx.

Click the hyperlink on the StepByStep8_2.asmx design view to switch to the code view. Change all the occurrences of Service1 to refer to StepByStep8_2. Add the following WebService attribute before the StepByStep8_2 class definition:

 [WebService(Namespace="http://NetExam.org/Balance")]

public class StepByStep8_2 :

    System.Web.Services.WebService

Add the following Web method definition to the Web service:

[WebMethod]

public decimal RetrieveBalance(short custNumber)

{

    NETMyCustomer.Balances b =

        new NETMyCustomer.Balances();

    return b.GetBalance(ref custNumber);

}

Set the Web service as the start page for the project.

Run the project. You should see that a browser is launched showing the test page. Click on the RetrieveBalance method link. Enter a number between 1 and 10 for the custNumber parameter and click the Invoke button. A second browser window opens with that customer's balance.

Add a Web service page named StepByStep8_3.asmx to the project.

Right-click the References node in Solution Explorer and select Add Reference.

Select the COM tab in the Add Reference dialog box. Scroll down the list of COM components until you come to the MyCustomer library. Select the MyCustomer library, click Select, and then click OK.

Add the following Web method definition to the Web service:

[WebMethod]

public decimal RetrieveBalance(short custNumber)

{

    MyCustomer.Balances b =

        new MyCustomer.Balances();

    return b.GetBalance(ref custNumber);

}

Set the Web service as the start page for the project.

Run the project. You should see that a browser is launched showing the test page. Click on the RetrieveBalance method link. Enter a number between 1 and 10 for the custNumber parameter and click the Invoke button. A second browser window opens with that customer's balance.

Launch Visual Basic 6. Create a new ActiveX DLL project.

Select the Project1 node in the Project Explorer window and rename it Numeric.

Select the Class1 node in the Project Explorer window and rename it Primes.

Add this code to the Primes class:

Option Explicit



Public Function HighPrime(Max As Long) As Long

        Dim a() As Byte

        Dim lngI As Long

        Dim lngJ As Long



        ReDim a(Max)



        ' In the array, 1 indicates a prime,

        ' 0 indicates nonprime.

        ' Start by marking multiples

        ' of 2 as nonprime

        For lngI = 0 To Max

            If lngI Mod 2 = 0 And lngI <> 2 Then

                a(lngI) = 0

            Else

                a(lngI) = 1

            End If

        Next lngI

      ' Now execute the usual sieve

      ' of erasthones algorithm

        For lngI = 3 To Sqr(Max) Step 2

            If a(lngI) = 1 Then

              ' This is a prime,

              ' so eliminate its multiples

                For lngJ = lngI + lngI To Max _

                    Step lngI

                    a(lngJ) = 0

                Next lngJ

            End If

        Next lngI

        ' Find the largest prime by working backwards

        For lngI = Max To 1 Step -1

            If a(lngI) = 1 Then

                HighPrime = lngI

                Exit For

            End If

        Next lngI

End Function

Save the Visual Basic project.

Select File, Build Numeric.dll to create the COM component.

In your Visual C# .NET project, right-click the References node of Solution Explorer and select Add Reference.

Select the COM tab in the Add Reference dialog box. Scroll down the list of COM components until you come to the Numeric library. Select the Numeric library, click Select, and then click OK.

Add a new class to your Visual C# .NET project. Name the class Primes.cs.

Add this code to the Primes.cs class:

using System;

public class Primes

{

    public int HighPrime(int max)

    {

        Byte[] a = new Byte[max];

        Int32 intI;

        Int32 intJ;



        // In the array, 1 indicates a prime,

        // 0 indicates nonprime. Start by marking

        // multiples of 2 as nonprime

        for(intI = 0;intI < max; intI++)

        {

            if((intI % 2 == 0) && (intI != 2))

                a[intI] = 0;

            else

                a[intI] = 1;

        }



        // Now execute the usual sieve

        // of erasthones algorithm

        for(intI = 3; intI <= System.Math.Sqrt(max);

            intI=intI+2)

        {

            if (a[intI] == 1)

            {

                // This is a prime,

                // so eliminate its multiples

                for(intJ = intI + intI; intJ < max;

                    intJ=intJ+intI)

                    a[intJ] = 0;

            }

        }

        // Find the largest prime by working backward

        for(intI = max-1; intI > 0; intI--)

        {

            if (a[intI] == 1)

            {

                break;

            }

        }

        return intI;

    }

}

Add a new Web service named GuidedPracticeExercise8_1.asmx to your Visual C# .NET project.

Switch to code view and add the following Web method definitions to the Web service definition:

[WebMethod]

public string CalculateCOMHighPrime(int maxNumber)

{

    Numeric.Primes COM_Primes = new Numeric.Primes();

    DateTime dt = DateTime.Now;

    Int32 intHighPrime =

        COM_Primes.HighPrime(ref maxNumber);

    TimeSpan ts = DateTime.Now.Subtract(dt);

    string COMResults = "High prime = " +

        intHighPrime.ToString() + " took " +

        ts.Ticks.ToString() + " ticks";

    return COMResults;

}



[WebMethod]

public string CalculateNETHighPrime(int maxNumber)

{

    Primes NET_Primes = new Primes();

    DateTime dt = DateTime.Now;

    Int32 intHighPrime =

        NET_Primes.HighPrime(maxNumber);

    TimeSpan ts = DateTime.Now.Subtract(dt);

    string NETResults = "High prime = " +

        intHighPrime.ToString() + " took " +

        ts.Ticks.ToString() + " ticks";



    return NETResults;

}

Set the Web service as the start page for the project.

Run the project. You should see that a browser is launched showing the test page. Click on the CalculateCOMHighPrime method link. Enter a fairly large number in the maxNumber parameter and click the Invoke button. The code finds the largest prime number that is smaller than the number you entered by using the COM library, and it displays the results as shown in Figure.

Click the Back button in the main page and then click on the CalculateNETHighPrime method link. Enter the same large number that you previously entered for the COM implementation in the maxNumber parameter and click the Invoke button. The code finds the largest prime number that is smaller than the number you entered using the native .NET class and displays the results as shown in Figure.