Example sharing on multi-threaded object creation in c#

The title of this article is about the problems I encountered when writing a blog in singleton mode, so I wrote a demo today to help me remember how to use multi-threading simply.

What I have been struggling with is how to instantiate the object multiple times in the for loop, so as to reproduce the error of multiple instance objects in the singleton mode without locking.

Let me first show you the multi-threaded instance object that I simply implemented.

Option 1:

Demo.cs

    public class Demo
    {        private static Demo _demo = null;        /// 

        /// 构造函数        /// 
        private Demo()
        {
            Console.WriteLine("构造了{0}", GetType().Name);
        }        /// 

        /// 获取该类的唯一实例        /// 
        /// 该类的唯一实例
        public static Demo GetInstance()
        {            if (_demo == null)
                _demo = new Demo();            return _demo;
        }
    }

Program.cs, client code

                Demo d1 = null;
                Demo d2 = null;                //多线程创建对象实例
                var t1 = new Thread(() => { d1 = Demo.GetInstance(); });                
                var t2 = new Thread(() => { d2 = Demo.GetInstance(); });

                t1.Start();
                t2.Start();
                Thread.Sleep(1000);//主线程等待子线程执行完成，为d1和d2变量赋值
                Console.WriteLine("d1 == d2 {0}", object.ReferenceEquals(d1, d2));
                Console.Read();

Output:

Outputting two objects with different references achieves what I want.

But in my mind, there has always been a way for the for loop to create instances in multiple threads, but I just can’t remember it. I accidentally saw this when I was checking information today. I will write down the method immediately, and then work overtime at night to write it out, so that I can have an impression in my mind.

Option 2:

Program.cs

                for (int i = 0; i < 2; i++)
                {                    
                new Action(() => { Demo.GetInstance(); }).BeginInvoke(null, null);
                }
                Console.Read();

Output:

In this way, when debugging singleton mode, you can reproduce the unadded The lock was wrong, and it also solved my doubts. I found a way to solve the problem of multi-threaded instance creation in a for loop.

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