[C#]Tuple Class

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字數統計: 559 | 閱讀時長 ≈ 2

function想要回傳多個值的好用類別

舊方法和缺點

  • 自訂class或struct，將想回傳的值包在裡面
    • 有時不是強烈內聚關係，只是單純放在一起，其實並不妥當
    • 有時只會被這個方法使用，無法重用
  • 透過物件的成員，經過方法後的狀態轉變，再取用
    • 若為static方法，可能有thread-safe問題
    • 回傳值的生命週期應該只在這個方法內
  • 使用 out 或 ref，在呼叫時先傳進來
    • 方法外面要先宣告，方法裡面要重新給值
    • 當回傳多個值會相當礙眼

Tuple Class(.NET Framework 4.0)

Tuple Class連結

簡單範例

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namespace App.Domain.Model
{
    using System;

    public class MemberInfo
    {
        public int MemberID { get; set; }

        public string NickName { get; set; }

        public string Email { get; set; }
    }
}

namespace App.Domain.Repository
{
    public interface IMemberInfoRepository
    {
        Tuple<Exception, MemberInfo> FindMemberInfo(int memberID);
    }
}

namespace App.Persistent.SQL
{
    public class MemberInfoRepository : IMemberInfoRepository
    {
        private string connectionString;

        public MemberInfoRepository(string connectionString)
        {
            this.connectionString = connectionString;
        }

        public Tuple<Exception, MemberInfo> FindMemberInfo(int memberID)
        {
            try
            {
                using (var conn = new SqlConnection(this.connectionString))
                {
                    var result = conn.QueryFirstOrDefault<MemberInfo>(
                        "SPName",
                        new
                        {
                            MemberID = memberID
                        },
                        commandType: CommandType.StoredProcedure);

                    return Tuple.Create<Exception, MemberInfo>(null, result);
                }
            }
            catch (Exception ex)
            {
                return Tuple.Create<Exception, MemberInfo>(ex, null);
            }
        }
    }
}

namespace App.Persistent.Tests
{
    [TestClass]
    public class MemberInfoRepositoryTests
    {
        private IMemberInfoRepository memberInfoRepo;

        [TestInitialize]
        public void Initialize()
        {
            this.memberInfoRepo = new MemberInfoRepository(ConfigHelper.SQLConnectionString);
        }

        [TestMethod]
        public void FindMemberInfo_Success_Test()
        {
            // Arrange
            int memberID = 100000;

            // Act
            var result = this.memberInfoRepo.FindMemberInfo(memberID);

            // Assert
            Assert.IsNull(result.Item1);
            Assert.IsNotNull(result.Item2);
            Assert.AreEqual(memberID, result.Item2.MemberID);
        }
    }
}

規範建議

  • 可讀性不佳(C# 7.0可自訂名稱): Tuple的Item不超過3個
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namespace App.Persistent.SQL
{
    public class MemberInfoRepository : IMemberInfoRepository
    {
        private string connectionString;

        public MemberInfoRepository(string connectionString)
        {
            this.connectionString = connectionString;
        }

        public (Exception ex, MemberInfo memberInfo) FindMemberInfo(int memberID)
        {
            try
            {
                using (var conn = new SqlConnection(this.connectionString))
                {
                    var result = conn.QueryFirstOrDefault<MemberInfo>(
                        "SPName",
                        new
                        {
                            MemberID = memberID
                        },
                        commandType: CommandType.StoredProcedure);

                    return (null, result);
                }
            }
            catch (Exception ex)
            {
                return (ex, null);
            }
        }
    }
}

namespace App.Persistent.Tests
{
    [TestClass]
    public class MemberInfoRepositoryTests
    {
        private IMemberInfoRepository memberInfoRepo;

        [TestInitialize]
        public void Initialize()
        {
            this.memberInfoRepo = new MemberInfoRepository(ConfigHelper.SQLConnectionString);
        }

        [TestMethod]
        public void FindMemberInfo_Success_Test()
        {
            // Arrange
            int memberID = 100000;

            // Act
            var result = this.memberInfoRepo.FindMemberInfo(memberID);

            // Assert
            Assert.IsNull(result.ex);
            Assert.IsNotNull(result.memberInfo);
            Assert.AreEqual(memberID, result.memberInfo.MemberID);
        }
    }
}
  • Summary註解中要說明各個Item代表的意義
  • 在Persistent中，Item1為Exception，Item2以後為回傳值
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