C# basic knowledge compilation: C# classes and structures (2)

　1. What is a constructor? What constructors are there? What are the definitions, implementation methods and precautions of each constructor?
The so-called constructor is a method that can initialize the object. That is, after running this function, the memory will always open up a space for objects of this class. There are three types: normal constructor, that is, instantiation constructor; private constructor; static constructor.
Instantiation constructor:

    public class Example
    {
        private string property1 = string.Empty;

        private string property2 = @"hello";

        private int property3 = 0;

        public Example()//成员都是声明时的初始值，这种默认的构造器，也可以不写。
        {

        }

        public Example(string p1, string p2, int p3)//传入的值初始化
        {
            this.property1 = p1;

            this.property2 = p2;

            this.property3 = p3;
        }
    }

Private constructor:
Private constructor is not accessible from the outside, so how to instantiate it? See the singleton mode. The private constructor is used here. ：

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Static constructor:
Look at the example first:

 public class StaticConstruct
    {
        static StaticConstruct()
        {
            Console.WriteLine(@"静态构造函数");
        }

        public StaticConstruct()
        {
            Console.WriteLine(@"实例化构造函数");
        }

        public StaticConstruct(string flage)
        {
            Console.WriteLine(@"带参构造函数");
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            StaticConstruct strc = new StaticConstruct();

            StaticConstruct strcValue = new StaticConstruct(string.Empty);

            Console.ReadLine();
        }
    }

Result:

Features of static constructors: Access modifiers are not allowed in static constructors; when instantiating, the static constructor is automatically called first, which means that calling the static constructor is uncontrollable; the static constructor has no parameters, and There is only one in a class; cannot be inherited.
　　2. What are the uses of This keyword and Base keyword? Implement code?
(1), this keyword:
This, as the name suggests, refers to the meaning in this class and refers to the members of the current class. Of course, if the program is running, it can be accurately said that this refers to the member of the object of the current class, and its function is to distinguish the object. Because a class can have N objects. However, the this keyword cannot be used in the static class. The reason is simply that static cannot instantiate multiple objects. It only has one, so there is no need to use this to distinguish objects. Generally used are as follows:
a. Variables with the same name in methods or constructors.

     public class MyTestA
    {
        private string testA = string.Empty;

        public MyTestA(string testA)
        {
            this.testA = testA;
        }

        public void Handler(string testA)
        {
            this.testA = testA;
        }
    }

b, get, set method

    public class MyTestB
    {
        private string testB = string.Empty;

        public string TestB
        {
            get 
            { 
                return this.testB;
            }
            set 
            { 
                this.testB = value;
            }
        }
    }

c, pass the instance
For example, in the event

    public class MyTestC
    {
        public event EventHandler OnTestCEvent = null;

        private void Send_OntestEvent(object sender,EventArgs e)
        {
            if (OnTestCEvent != null)
            {
                OnTestCEvent(sender, e);
            }
        }

        private void TestEvent()
        {
            Send_OntestEvent(this, null);
        }
    }

    public class MyTestD
    {
        MyTestC testC = new MyTestC();

        public event EventHandler OnTestDEvent = null;

        private void Send_OnTestDEvent(object sender, EventArgs e)
        {
            if (OnTestDEvent != null)
            {
                OnTestDEvent(sender, e);
            }
        }

        public MyTestD()
        {
            testC.OnTestCEvent += new EventHandler(testC_OnTestEvent);
        }

        void testC_OnTestEvent(object sender, EventArgs e)
        {
            Send_OnTestDEvent(sender, e);
        }
    }

    public class MyTestE
    {
        MyTestD testD = new MyTestD();

        public MyTestE()
        {
            this.testD.OnTestDEvent += new EventHandler(testD_OnTestDEvent);
        }

        void testD_OnTestDEvent(object sender, EventArgs e)
        {
            MyTestC testC = sender as MyTestC;//通过MytestD将对象转了过来

            if (testC != null)
            {
                //代码
            }
        }
    }

(2) base keyword:
General Used by subclasses to access parent classes.
One is when overriding the parent class method,

    public class ParentClass
    {
        public virtual void MethodA()
        {
            Console.WriteLine(@"基类的方法");
        }
    }

    public class ChildClass : ParentClass
    {
        public override void MethodA()
        {
            base.MethodA();

            Console.WriteLine("派生类方法");
        }
    }

The other is when the subclass calls the parent class constructor,

    public class ParentClass
    {
        public ParentClass(string flage)
        {
            Console.WriteLine(@"基类构造函数");
        }

        public virtual void MethodA()
        {
            Console.WriteLine(@"基类的方法");
        }
    }

    public class ChildClass : ParentClass
    {
        public ChildClass(string flage)

            : base(flage)
        {

        }

        public override void MethodA()
        {
            base.MethodA();

            Console.WriteLine("派生类方法");
        }
    }

　 3. What is reflection? How to implement reflection? What are the advantages and disadvantages of reflection? When to use reflection?
http://blog.csdn.net/yysyangyangyangshan/article/details/7028589

The above is the basic knowledge of C#: C# class and structure (2). For more related content, please pay attention to the PHP Chinese website (m.sbmmt.com)!