【保険商品管理システムの開発】自動車保険のコントローラーの作成

コード

Controllers/AutoInsuranceController.cs

using Microsoft.AspNetCore.Mvc;
using InsuranceProductManager.Models;
using System;
using System.Collections.Generic;
using System.Linq;

namespace InsuranceProductManager.Controllers
{
    [ApiController]
    [Route("api/[controller]")]
    public class AutoInsuranceController : ControllerBase
    {
        // 架空の料率テーブル
        private readonly List<AutoInsuranceRate> _rateTable = new()
        {
            new AutoInsuranceRate { VehicleClass = "軽自動車", AgeGroup = "全年齢", BaseRate = 0.06m, GenderFactorMale = 1.05m, GenderFactorFemale = 1.00m },
            new AutoInsuranceRate { VehicleClass = "軽自動車", AgeGroup = "21歳以上", BaseRate = 0.05m, GenderFactorMale = 1.03m, GenderFactorFemale = 1.00m },
            new AutoInsuranceRate { VehicleClass = "軽自動車", AgeGroup = "26歳以上", BaseRate = 0.04m, GenderFactorMale = 1.00m, GenderFactorFemale = 0.98m },
            new AutoInsuranceRate { VehicleClass = "普通車", AgeGroup = "全年齢", BaseRate = 0.08m, GenderFactorMale = 1.07m, GenderFactorFemale = 1.00m },
            new AutoInsuranceRate { VehicleClass = "普通車", AgeGroup = "21歳以上", BaseRate = 0.07m, GenderFactorMale = 1.05m, GenderFactorFemale = 1.00m },
            new AutoInsuranceRate { VehicleClass = "普通車", AgeGroup = "26歳以上", BaseRate = 0.06m, GenderFactorMale = 1.02m, GenderFactorFemale = 0.98m }
        };

        [HttpPost("calculate")]
        public ActionResult<AutoInsuranceCalculationResult> Calculate(AutoInsuranceCalculationRequest request)
        {
            // 該当する料率を取得
            var rate = _rateTable.FirstOrDefault(r =>
                r.VehicleClass == request.VehicleClass &&
                r.AgeGroup == request.AgeGroup
            );

            if (rate == null)
            {
                return BadRequest("該当する料率が見つかりません。");
            }

            // 性別補正
            decimal genderFactor = request.Gender == "男性" ? rate.GenderFactorMale : rate.GenderFactorFemale;

            // 等級割引・割増（20等級で-60%、1等級で+60%という例）
            decimal gradeFactor = request.Grade switch
            {
                >= 20 => 0.40m,
                >= 15 => 0.60m,
                >= 10 => 0.80m,
                >= 6 => 1.00m,
                _ => 1.60m
            };

            // 走行距離補正
            decimal mileageFactor = request.AnnualMileage switch
            {
                <= 5000 => 0.95m,
                <= 10000 => 1.00m,
                <= 15000 => 1.05m,
                _ => 1.10m
            };

            // オプション補正
            decimal optionFactor = 1.00m;
            if (request.IncludeVehicleDamage) optionFactor += 0.25m;
            if (request.IncludePersonalInjury) optionFactor += 0.15m;
            if (request.IncludeLawyerService) optionFactor += 0.05m;

            // 年間保険料計算（仮の計算式）
            decimal annualPremium = 300000 * rate.BaseRate * genderFactor * gradeFactor * mileageFactor * optionFactor;

            // 総保険料
            decimal totalPremium = annualPremium * request.Years;

            // 詳細内訳
            string details = $"車種: {request.VehicleClass}, 年齢条件: {request.AgeGroup}, 性別: {request.Gender}, " +
                             $"基本料率: {rate.BaseRate:P}, 等級補正: {gradeFactor}, 走行距離補正: {mileageFactor}, オプション補正: {optionFactor}";

            return new AutoInsuranceCalculationResult
            {
                AnnualPremium = Math.Round(annualPremium, 0),
                TotalPremium = Math.Round(totalPremium, 0),
                Details = details
            };
        }
    }
}

解説

Controllers/AutoInsuranceController.cs

            // 該当する料率を取得
            var rate = _rateTable.FirstOrDefault(r =>
                r.VehicleClass == request.VehicleClass &&
                r.AgeGroup == request.AgeGroup
            );

上記で_rateTableから基本料率、男性補正と女性補正を取得。

Controllers/AutoInsuranceController.cs

   // 性別補正
            decimal genderFactor = request.Gender == "男性" ? rate.GenderFactorMale : rate.GenderFactorFemale;

request.Genderが男性か女性で、genderFactorに性別補正を代入。

Controllers/AutoInsuranceController.cs

            // 等級割引・割増（20等級で-60%、1等級で+60%という例）
            decimal gradeFactor = request.Grade switch
            {
                >= 20 => 0.40m,
                >= 15 => 0.60m,
                >= 10 => 0.80m,
                >= 6 => 1.00m,
                _ => 1.60m
            };

request.Gradeの等級によって、割引・割増(0.40m等)を行う。

Controllers/AutoInsuranceController.cs

            decimal mileageFactor = request.AnnualMileage switch
            {
                <= 5000 => 0.95m,
                <= 10000 => 1.00m,
                <= 15000 => 1.05m,
                _ => 1.10m
            };

request.AnnualMileageの数値によって、割引・割増(0.95m等)を行う。

Controllers/AutoInsuranceController.cs

            // オプション補正
            decimal optionFactor = 1.00m;
            if (request.IncludeVehicleDamage) optionFactor += 0.25m;
            if (request.IncludePersonalInjury) optionFactor += 0.15m;
            if (request.IncludeLawyerService) optionFactor += 0.05m;

requestの各変数がtrueであれば、オプション係数を+0.25します。

Controllers/AutoInsuranceController.cs

            // 年間保険料計算（仮の計算式）
            decimal annualPremium = 300000 * rate.BaseRate * genderFactor * gradeFactor * mileageFactor * optionFactor;

            // 総保険料
            decimal totalPremium = annualPremium * request.Years;

掛け算をしてannualPremium、totalPremiumに代入しています。

Controllers/AutoInsuranceController.cs

            // 詳細内訳
            string details = $"車種: {request.VehicleClass}, 年齢条件: {request.AgeGroup}, 性別: {request.Gender}, " +
                             $"基本料率: {rate.BaseRate:P}, 等級補正: {gradeFactor}, 走行距離補正: {mileageFactor}, オプション補正: {optionFactor}";

各計算結果に各文字列(車種:)を合わせた内容をdetailsに代入しています。

Controllers/AutoInsuranceController.cs

            return new AutoInsuranceCalculationResult
            {
                AnnualPremium = Math.Round(annualPremium, 0),
                TotalPremium = Math.Round(totalPremium, 0),
                Details = details
            };

上記のReturn文の内容が画面で取得できます。