運算符與類型轉換

1.運算符

（1）分類

算術運算符、關係運算符、邏輯運算符、位運算符、賦值運算符、其他運算符

>.算術運算符:

>.關係運算符:

using System;

namespace study
{
    public class demo0_operator
    {
        static void Main(string[] args)
        {
            UserControl u1 = new UserControl("1", 2, 3);
            UserControl u2 = new UserControl("1", 4, 5);
            Console.WriteLine("hashcode of u1 is=" + u1.GetHashCode());
            Console.WriteLine("hashcode of u2 is=" + u2.GetHashCode());
            Console.WriteLine("u1==u2 is " + (u1 == u2));

            //demo string
            string s1 = "hello word";
            string s2 = "hello word";
            string s3 = "hello " + "word";
            Console.WriteLine("hashcode of s1 is=" + s1.GetHashCode());
            Console.WriteLine("hashcode of s2 is=" + s2.GetHashCode());
            Console.WriteLine("hashcode of s3 is=" + s3.GetHashCode());
            Console.WriteLine("s1==s2 is " + (s1 == s2));
            Console.WriteLine("s1==s3 is " + (s1 == s3));

            //運行結果如下:
            
            // hashcode of u1 is=1062342447
            // hashcode of u2 is=472133479
            // u1==u2 is True
            // hashcode of s1 is=-645689584
            // hashcode of s2 is=-645689584
            // hashcode of s3 is=-645689584
            // s1==s2 is True

        }
    }

    public class UserControl
    {
        public string id;
        public int width;
        public int height;

        public UserControl(string id, int width, int height)
        {
            this.id = id;
            this.width = width;
            this.height = height;
        }

        public static bool operator ==(UserControl lhs, UserControl rhs)
        {
            return lhs.id == rhs.id;
        }

        public static bool operator !=(UserControl lhs, UserControl rhs)
        {
            return !(lhs == rhs);
        }

        public override bool Equals(object obj)
        {
            if (obj is UserControl) return false;
            return this == (UserControl)obj;
        }

        public override int GetHashCode()
        {
            return this.ToString().GetHashCode();
        }

        public override string ToString()
        {
            return "控制項id:" + this.id + "寬度" + this.width + "；高度：" + this.height;
        }

    }
}

>.邏輯運算符:

>.位運算符:

位運算符作用於位，並逐位執行操作。&、 | 和 ^ 的真值表如下所示

>.賦值運算符:

 >.其他運算符:

using System;

namespace study
{
    public class demo2_reflection
    {
        private string currentType = typeof(demo2_reflection).ToString();

        private string value;

        public demo2_reflection(string value)
        {
            this.value = value;
        }

        public void showName()
        {
            Console.WriteLine("currentType is " + currentType);
            Console.WriteLine("value=" + this.value);
        }

        static void Main(string[] args)
        {
            Type t = Type.GetType("study.demo2_reflection");
            Console.WriteLine("type of t is "+t.GetType().ToString());
            Object[] constructParms = new object[] {"hello word"};  //構造器參數
            demo2_reflection obj = (demo2_reflection)Activator.CreateInstance(t, constructParms);
            obj.showName();
        }
    }


}

2.運算符優先順序

2.類型轉換

C#里的類型轉換

(1)隱式轉換

從類型A到類型B的轉換可以在所有情況下進行，執行轉換的規則非常簡單，可以讓編譯器執行轉換。

隱式轉換不需要做任何工作，也不需要另外編寫代碼。如將int型數據轉換成double型數據：

int a = 10;
double b = a;//隱式轉換

(2)顯式轉換

從類型A到類型B的轉換隻能在某些情況下進行，轉換規則比較複雜，應進行某種類型的額外處理。顯式轉換又叫強制類型轉換，顯式轉換需要用戶明確的指定轉換類型。如將double類型數據轉換成int類型數據：

double c = 10.5;
int d = (int)c;//顯示轉換

(3)通過方法進行類型轉換

using System;

namespace study
{
    public static class  typeConversion
    {
        public static string timeToString(DateTime value)
        {
            return value.ToString("yyyy-MM-dd HH:mm:ss fff");
        }

        public static string timeToStringEx(this DateTime value)
        {
            return value.ToString("yyyy-MM-dd HH:mm:ss fff");
        }

        static void Main(string[] args)
        {
            DateTime now=DateTime.Now;
            Console.WriteLine("timeToString="+typeConversion.timeToString(now));
            Console.WriteLine("timeToStringEx="+now.timeToStringEx());
        }
    }
}

using System;

namespace study
{
    public class typeConversion
    {
        static IUserControl getInstance(string controlName)
        {
            switch (controlName)
            {
                case "TextBox":
                    return new User_TextBox();
                case "Dropdown":
                    return new User_Dropdown();
                default:
                    return new User_TextBox();
            }


        }
        static void Main(string[] args)
        {
            IUserControl contorl1 = new User_TextBox();
            IUserControl contorl2 = new User_Dropdown();

            Console.WriteLine("type of contorl1" + contorl1.GetType().ToString());
            Console.WriteLine("type of contorl2" + contorl2.GetType().ToString());

            IUserControl contorl3 = (IUserControl)contorl2;
            Console.WriteLine("type of contorl3" + contorl3.GetType().ToString());

            IUserControl contorl4 = getInstance("TextBox");
            IUserControl contorl5 = getInstance("Dropdown");

            Console.WriteLine("type of contorl4" + contorl4.GetType().ToString());
            Console.WriteLine("type of contorl5" + contorl5.GetType().ToString());

        }

    }

    public interface IUserControl
    {
        void getControl();
        void checkdata();
        void resetControl();
    }

    public class User_TextBox : IUserControl
    {
        public void checkdata()
        {
            Console.WriteLine("checkdata is User_TextBox");
        }

        public void getControl()
        {
            Console.WriteLine("getControl is User_TextBox");
        }

        public void resetControl()
        {
            Console.WriteLine("resetControl is User_TextBox");
        }
    }
    public class User_Dropdown : IUserControl
    {
        public void checkdata()
        {
            Console.WriteLine("checkdata is User_Dropdown");
        }

        public void getControl()
        {
            Console.WriteLine("getControl is User_Dropdown");
        }

        public void resetControl()
        {
            Console.WriteLine("resetControl is User_Dropdown");
        }
    }

}