Esempio di interoperabilità COM: client .NET e server COM

Articolo
05/10/2023

Questo esempio illustra come un client .NET, compilato per accedere a un server COM, crea un'istanza di una coclasse COM e chiama membri della classe per eseguire calcoli relativi a un mutuo.

In questo esempio il client crea e chiama un'istanza della coclasse Loan, passa quattro argomenti, uno dei quali uguale a zero, all'istanza e visualizza i calcoli. Diversi frammenti di codice di questo esempio vengono presentati in vari punti della sezione.

Client .NET

Imports System  
Imports Microsoft.VisualBasic  
Imports LoanLib  
  
Public Class LoanApp  
  
    Public Shared Sub Main()  
        Dim Args As String()  
        Args = System.Environment.GetCommandLineArgs()  
  
        Dim ln As New Loan()  
  
        If Args.Length < 5 Then  
            Console.WriteLine("Usage: ConLoan Balance Rate Term Payment")  
            Console.WriteLine(" Either Balance, Rate, Term, or Payment " _  
                                & "must be 0")  
            Exit Sub  
        End If  
  
        ln.OpeningBalance = Convert.ToDouble(Args(1))  
        ln.Rate = Convert.ToDouble(Args(2)) / 100.0  
        ln.Term = Convert.ToInt16(Args(3))  
        ln.Payment = Convert.ToDouble(Args(4))  
  
        If ln.OpeningBalance = 0.0 Then  
            ln.ComputeOpeningBalance()  
        End If  
        If ln.Rate = 0.0 Then  
            ln.ComputeRate()  
        End If  
        If ln.Term = 0 Then  
            ln.ComputeTerm()  
        End If  
        If ln.Payment = 0.0 Then  
            ln.ComputePayment()  
        End If
        Console.WriteLine("Balance = {0,10:0.00}", ln.OpeningBalance)  
        Console.WriteLine("Rate    = {0,10:0.0%}", ln.Rate)  
        Console.WriteLine("Term    = {0,10:0.00}", ln.Term)  
        Console.WriteLine("Payment = {0,10:0.00}" & ControlChars.Cr, _  
                          ln.Payment)  
  
        Dim MorePmts As Boolean  
        Dim Balance As Double = 0.0  
        Dim Principal As Double = 0.0  
        Dim Interest As Double = 0.0  
  
        Console.WriteLine("{0,4}{1,10}{2,12}{3,10}{4,12}", _  
           "Nbr", "Payment", "Principal", "Interest", "Balance")  
        Console.WriteLine("{0,4}{1,10}{2,12}{3,10}{4,12}", _  
           "---", "-------", "---------", "--------", "-------")  
  
        MorePmts = ln.GetFirstPmtDistribution(ln.Payment, Balance, _  
           Principal, Interest)  
  
        Dim PmtNbr As Short  
  
        While MorePmts  
  
            Console.WriteLine("{0,4}{1,10:0.00}{2,12:0.00}{3,10:0.00}" _  
              & "{4,12:0.00}", PmtNbr, ln.Payment, Principal, Interest,  
              Balance)  
            MorePmts = ln.GetNextPmtDistribution(ln.Payment, Balance, _  
              Principal, Interest)  
            PmtNbr += CShort(1)  
        End While  
    End Sub  
End Class

using System;  
using LoanLib;  
  
public class LoanApp {  
   public static void Main(String[] Args) {  
  
      Loan ln = new Loan();  
  
      if (Args.Length < 4)
      {  
         Console.WriteLine("Usage: ConLoan Balance Rate Term Payment");  
         Console.WriteLine("    Either Balance, Rate, Term, or Payment
            must be 0");  
         return;  
      }  
  
      ln.OpeningBalance = Convert.ToDouble(Args[0]);  
      ln.Rate = Convert.ToDouble(Args[1])/100.0;  
      ln.Term = Convert.ToInt16(Args[2]);  
      ln.Payment = Convert.ToDouble(Args[3]);  
  
      if (ln.OpeningBalance == 0.00) ln.ComputeOpeningBalance();  
      if (ln.Rate == 0.00) ln.ComputeRate();  
      if (ln.Term == 0) ln.ComputeTerm();  
      if (ln.Payment == 0.00) ln.ComputePayment();  
  
      Console.WriteLine("Balance = {0,10:0.00}", ln.OpeningBalance);  
      Console.WriteLine("Rate    = {0,10:0.0%}", ln.Rate);  
      Console.WriteLine("Term    = {0,10:0.00}", ln.Term);  
      Console.WriteLine("Payment = {0,10:0.00}\n", ln.Payment);  
  
      bool MorePmts;  
      double Balance = 0.0;  
      double Principal = 0.0;  
      double Interest = 0.0;  
  
      Console.WriteLine("{0,4}{1,10}{2,12}{3,10}{4,12}", "Nbr", "Payment",  
        "Principal", "Interest", "Balance");  
      Console.WriteLine("{0,4}{1,10}{2,12}{3,10}{4,12}", "---", "-------",  
        "---------", "--------", "-------");  
  
      MorePmts = ln.GetFirstPmtDistribution(ln.Payment, out Balance,
        out Principal, out Interest);  
  
      for (short PmtNbr = 1; MorePmts; PmtNbr++) {  
         Console.WriteLine("{0,4}{1,10:0.00}{2,12:0.00}{3,10:0.00}  
           {4,12:0.00}", PmtNbr, ln.Payment, Principal, Interest,  
            Balance);  
         MorePmts = ln.GetNextPmtDistribution(ln.Payment, ref Balance,
           out Principal, out Interest);
      }  
    }  
}

Server COM

// Loan.cpp : Implementation of CLoan  
#include "stdafx.h"  
#include "math.h"  
#include "LoanLib.h"  
#include "Loan.h"  
  
static double Round(double value, short digits);
  
STDMETHODIMP CLoan::get_OpeningBalance(double *pVal)  
{  
    *pVal = OpeningBalance;  
    return S_OK;  
}  
  
STDMETHODIMP CLoan::put_OpeningBalance(double newVal)  
{  
    OpeningBalance = newVal;  
    return S_OK;  
}  
  
STDMETHODIMP CLoan::get_Rate(double *pVal)  
{  
    *pVal = Rate;  
    return S_OK;  
}  
  
STDMETHODIMP CLoan::put_Rate(double newVal)  
{  
    Rate = newVal;  
    return S_OK;  
}  
  
STDMETHODIMP CLoan::get_Payment(double *pVal)  
{  
    *pVal = Payment;  
    return S_OK;  
}  
  
STDMETHODIMP CLoan::put_Payment(double newVal)  
{  
    Payment = newVal;  
    return S_OK;  
}  
  
STDMETHODIMP CLoan::get_Term(short *pVal)  
{  
    *pVal = Term;  
    return S_OK;  
}  
  
STDMETHODIMP CLoan::put_Term(short newVal)  
{  
    Term = newVal;  
    return S_OK;  
}  
  
STDMETHODIMP CLoan::ComputePayment(double *pVal)  
{  
    Payment = Round(OpeningBalance * (Rate /
        (1 - pow((1 + Rate), -Term))),2);  
    *pVal = Payment;  
    return S_OK;  
}  
  
STDMETHODIMP CLoan::ComputeOpeningBalance(double *pVal)  
{  
    OpeningBalance = Round(Payment / (Rate /
        (1 - pow((1 + Rate), -Term))),2);  
    *pVal = OpeningBalance ;  
    return S_OK;  
}  
  
STDMETHODIMP CLoan::ComputeRate(double *pVal)  
{  
    double DesiredPayment = Payment;  
  
    for (Rate = 0.001; Rate < 28.0; Rate += 0.001)  
    {  
        Payment = Round(OpeningBalance * (Rate /
         (1 - pow((1 + Rate), -Term))),2);  
  
        if (Payment >= DesiredPayment)  
            break;  
    }  
  
    *pVal = Rate;
    return S_OK;  
}  
  
STDMETHODIMP CLoan::ComputeTerm(short *pVal)  
{  
    double DesiredPayment = Payment;  
    for (Term = 1; Term < 480 ; Term ++)  
    {  
        Payment = Round(OpeningBalance * (Rate /
         (1 - pow((1 + Rate), -Term))),2);  
        if (Payment <= DesiredPayment)  
            break;  
    }  
    *pVal = Term;
    return S_OK;  
}  
  
STDMETHODIMP CLoan::GetFirstPmtDistribution(double PmtAmt, double *Balance, double *PrinPortion, double *IntPortion, VARIANT_BOOL *pVal)  
{  
    *Balance = OpeningBalance;  
    GetNextPmtDistribution(PmtAmt, Balance, PrinPortion, IntPortion,
      pVal);  
    return S_OK;  
}  
  
STDMETHODIMP CLoan::GetNextPmtDistribution(double PmtAmt, double *Balance, double *PrinPortion, double *IntPortion, VARIANT_BOOL *pVal)  
{  
    *IntPortion = Round(*Balance * Rate, 2);  
    *PrinPortion = Round(PmtAmt - *IntPortion, 2);  
    *Balance = Round(*Balance - *PrinPortion, 2);  
  
    if (*Balance <= 0.0)  
        *pVal = FALSE;  
    else  
        *pVal = TRUE;  
    return S_OK;  
}  
  
STDMETHODIMP CLoan::get_RiskRating(BSTR *pVal)  
{  
    *pVal = (BSTR)RiskRating;  
    return S_OK;  
}  
  
STDMETHODIMP CLoan::put_RiskRating(BSTR newVal)  
{  
    RiskRating = newVal;  
    return S_OK;  
}  
static double Round(double value, short digits)
{  
    double factor = pow(10, digits);  
    return floor(value * factor + 0.5)/factor;  
}

Vedi anche

Esposizione di componenti COM a .NET Framework

Condividi tramite

Esempio di interoperabilità COM: client .NET e server COM

Client .NET

Server COM

Vedi anche

Risorse aggiuntive