. NET Framework-Detailed introduction to WinForm Mortgage Analyzer (GRAPHIC)

Problem

Buy a house loan, choose the equal interest or an equal amount of capital? How much interest do you pay for each?
How much did you pay for the principal and how much did you pay interest on the monthly loan?
If the loan 30, can calculate the 360 months, the monthly repayment details?
Do you know there are several ways to repay a large sum? How much money can you save after a large repayment?

Background

There are 2 ways to borrow from a bank: equal principal, equal and principal interest. equal to the principal, the monthly repayment amount of the principal is fixed, such as loan 300,000, 30 pay off, the first month about 2100 yuan, of which the principal 800 yuan, the interest of more than 1200 yuan, the principal of each month is these, this method, the resulting interest rate less than the equal. equal principal and interest, the monthly repayment of the principal and interest is fixed, the same loan 300,000, 30 to pay off, take this way, every month to repay nearly 1600 yuan, although monthly than the equivalent principal repayment less, but the repayment period, the interest rate is more than the equivalent of the principal.

Mortgage Analyzer

Software source Open source, GitHub download Address: Despositor Source: Visual Studio C#.net, Welcome to download.

Support Features

1) Support the configuration of loan information; 2) support two types of loan, repayment situation and monthly details: principal, principal, interest, interest rate; 3) Large repayment, currently only support a large repayment method: Shorten the repayment cycle mode, the latest repayment situation and details; 4) provide paging browse display function.

Software architecture

Public 4-tier structure: The LIB layer, provides the XML loan configuration Local preservation service, the business model layer, the business logic layer, the interface layer. The main objects include:
Model layer:Imroot: Model root interface;mdebt: Loan model Base Object;mequalcaptial: equal principal model object;mequalinterest: The matching principal and interest model object.
Business layer:debtanalysis: Provide business logic of loan correlation analysis;BasebigrepayLarge repayment business analysis of the base class, the reason for the separation of this object, because there are many methods of large repayment;Shortmonthsbigrepay: Shorten the period of large repayment base class;ibigrepaydebtLarge repayment interface;ShortMonthsBigRepayS1: The loan method is equal to the principal;ShortMonthsBigRepayS2: The loan method is equal and principal.
Interface layer:Basedlg: The master page of the page, the root class of all pages;Basesettingdlg: Loan Allocation Base dialog box;Debtsettingdlg: Loan Configuration dialog box;Debtanalysisdlg: Loan Analysis dialog box;Detaildebtdlg: Loan Details dialog box;MainForm: The main interface of the software.
The UML diagram of the software structure is as follows:
　　

　　
　　

Test

Assuming the loan amount is 300,000, the loan duration 30, the loan method is: the equal principal, the loan annual interest rate is 4.9%, assumes the loan starting date is October 2015.
Open the software, the interface as shown, click on the "Loan settings", in this interface, enter the loan information, set up, click Save, configuration information to save to local.

Next, start the repayment situation analysis, click on the loan analysis , the loan analysis interface as shown below. Analysis results show that the amount has also been displayed, has also the principal and principal: 32,500, has also the capital: 13,300, has also interest: 19,100, we can see how the bank to make money?!

In this interface, click on the "Details" button to get the amount of a detailed chart :

Never the column can be seen, the amount of unpaid interest: 488,600, the Principal: 286,700, Interests: 201,900. The details of the unpaid amount are shown below:

Large repayment

As you can see, the interest rate at the beginning of repayment is still very high ah, about 60%. So, a little money on hand, or appropriate more loans Ah! Click on the "Early Repayment" button, enter a large repayment time: "2017-02", enter the large amount of repayment 100,000, click "Calculate".
　　

Get not also principal, principal, interest, save interest, we can see can be less than 110,000 more! From the bar chart can also be seen, save a lot of money AH!!! Click "Details", you can page through the large repayment after the monthly repayment situation:

Comparison of large repayment before and after:

Rate

Repayment	Time	principal	principal	Interest	Interest
Before a large repayment	2019-3	1922	833	1089	57%
After large repayment	2019-3	1514	833	681	45%

　　
From the figure, you pay less interest after a large repayment, and the interest rate is reduced by 12 points.