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COM Interop 範例:.NET 用戶端與 COM 伺服器

更新:2007 年 11 月

這個範例展示建置用來存取 COM 伺服器的 .NET 用戶端如何建立 COM Coclass 執行個體,以及呼叫類別成員以執行抵押貸款計算。

在這個範例中,用戶端會建立並呼叫 Loan Coclass 的執行個體、傳遞四個引數 (其中一個等於零) 給執行個體,並且顯示這項運算。這個範例的程式碼片段會出現在這個章節的各個地方。

.NET 用戶端

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); 
      }
    }
}

COM 伺服器

// 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;
}

請參閱

概念

將 COM 元件公開給 .NET Framework