C# Singleton Mechanism 實作練習

CS_Singleton_ex1.cs

/// <summary>
/// Single mechanism
/// 使用 static 靜態宣告實作
/// 此案例為：設定取用系統組態
/// </summary>
internal class MyCfg2
{
    private MyCfg2() { }

    //# configuration properties
    public static string SourceDir
    {
        get;
        set;
    }

    public static string TargetDir
    {
        get;
        set;
    }

    public static AnalysisCfg Analysis
    {
        get;
        set;
    }

    /// 模擬第二層的組態設定
    internal class AnalysisCfg
    {
        //private AnalysisCfg() {} // sealed this constructor.

        public AnalysisCfg(string mode, string start_pos)
        {
            this.Mode = mode;
            this.StartPos = start_pos;
        }

        public string Mode { get; protected set; }
        public string StartPos { get; protected set; }
    }

}

//## 應用 =========================================================
//# get value 
MyCfg2.SourceDir = "the source dir";
MyCfg2.TargetDir = "the target dir";
MyCfg2.Analysis = new MyCfg2.AnalysisCfg("my mode", "begin");

//# get value
string source_dir = MyCfg2.SourceDir;
string target_dir = MyCfg2.TargetDir;
MyCfg2.AnalysisCfg analysis2 = MyCfg2.Analysis;

CS_Singleton_ex2.cs

/// <summary>
/// Single mechanism & Fluent interface
/// 加入fluent interface 讓coding時有親和力一些。
/// 此案例為：設定取用系統組態
/// </summary>
internal class MyCfg
{
    #region Singleton Mechanism

    static MyCfg _instance = new MyCfg();
    
    private MyCfg() { }

    public static MyCfg Define { 
        get { return _instance; } 
    }

    #endregion

    #region configuration preperties
    
    private string _sourceDir;
    private string _targetDir;
    private AnalysisCfg _analysis;

    /// <summary>
    /// 模擬第二層的組態設定
    /// </summary>
    internal class AnalysisCfg
    {
        //private AnalysisCfg() {} // sealed this constructor.

        public AnalysisCfg(string mode, string start_pos)
        {
            this.Mode = mode;
            this.StartPos = start_pos;
        }

        public string Mode { get; protected set; }
        public string StartPos { get; protected set; }
    }

    #endregion

    #region handling - get cfg
    
    public static string SourceDir
    {
        get { return _instance._sourceDir; }
    }

    public static string TargetDir
    {
        get { return _instance._targetDir; }
    }

    public static AnalysisCfg Analysis
    {
        get { return _instance._analysis; }
    }
    
    #endregion

    #region handling - set cfg

    public MyCfg SetSourceDir(string source_dir)
    {
        _instance._sourceDir = source_dir;
        return this;
    }

    public MyCfg SetTargetDir(string target_dir)
    {
        _instance._targetDir = target_dir;
        return this;
    }

    public MyCfg SetAnalysis(AnalysisCfg analysis_cfg)
    {
        _instance._analysis = analysis_cfg;
        return this;
    }

    #endregion
}

//## 應用 =========================================================
//# set value
MyCfg.Define
    .SetSourceDir("the source dir")
    .SetTargetDir("the target dir")
    .SetAnalysis(new MyCfg.AnalysisCfg("my mode", "begin"));

//# get value
string source_dir = MyCfg.SourceDir;
string target_dir = MyCfg.TargetDir;
MyCfg.AnalysisCfg analysis = MyCfg.Analysis;

cs_Singleton_lazy.cs

/// <summary>
/// singleton lazy 建構版
/// </summary>
public class FooSingleton
{
    #region Singleton
    private readonly static Lazy<FooSingleton> _instance = new Lazy<FooSingleton>(
        () => new FooSingleton());
        
    public static FooSingleton Instance
    {
        get
        {
            return _instance.Value;
        }
    }
    #endregion
    
    ...
}

Singleton_logging.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Web;

namespace MPB.MTNET.IM.Web.Helpers
{
    public class Common2
    {
        #region Singleton Mechanism

        private static Common2 _singleton = new Common2();

        private Common2() { }

        public static Common2 Singleton
        {
            get { return _singleton; }
        }

        #endregion

        //## properties
        private string _defaultClassName = "System";

        /// <summary>
        /// 指定預設的 logging 類別名稱(功能大分類)。
        /// </summary>
        public static string DefaultClassName {
            get {
                return _singleton._defaultClassName;
            }
            set {
                _singleton._defaultClassName = value;
            }
        }


        /// <summary>
        /// helper function : logging
        /// </summary>
        /// <param name="message">訊息</param>
        /// <param name="desc">進一步資訊，如：stack trace 等利於除錯的資訊</param>
        /// <param name="methodName">CallerMemberName</param>
        public static void LogMessage(string message, string desc = null, [CallerMemberName] string methodName = "")
        {
            LogMessage(message, desc, methodName, _singleton._defaultClassName);
        }
        
        /// <summary>
        /// helper function : logging
        /// </summary>
        /// <param name="className">類別名稱、功能大分類</param>
        /// <param name="methodName">成員函式名稱、功能次分類</param>
        /// <param name="message">訊息</param>
        /// <param name="desc">進一步資訊，如：stack trace 等利於除錯的資訊</param>
        public static void LogMessage(string message, string desc, string methodName, string className)
        {
            try
            {
#if DEBUG
                Debug.WriteLine(string.Format("LogMessage >> {0}.{1} {2} {3}", className, methodName, message, desc));
#endif

                // write system log data table
                using (YourDBEntities ctx = new YourDBEntities())
                {
                    DateTime now = DateTime.Now;
                    string sql = @"INSERT INTO [dbo].[your_system_log]
                                    ([class_name]
                                    ,[method_name]
                                    ,[error_message]
                                    ,[error_desc]
                                    ,[log_date]
                                    ,[log_time])
                                    VALUES
                                    (@p0,@p1,@p2,@p3,@p4,@p5)";

                    // 只是INSERT，直接跑SQL比較快。
                    ctx.Database.ExecuteSqlCommand(sql, className, methodName, message, desc, now.ToString("yyyyMMdd"), now.ToString("HHmmss"));
                }
            }
            catch
            {
                // log 就算失敗系統也要能續續運轉。
            }
        }
    }

}