csharp: Use of Is and As operators in csharp

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/// <summary>     /// Geovin Du 20170622     /// </summary>     /// <param name="sender"></param>     /// <param name="e"></param>     private void button1_Click(object sender, EventArgs e)     {         Object o = new Object();         System.Boolean b1 = (o is System.Object);//b1 为true         System.Boolean b2 = (o is Employee);//b2为false           if (o is Employee)         {             Employee em = (Employee)o;             em.RealName = "geovindu";             MessageBox.Show(em.RealName);         }         else         {             MessageBox.Show("no"); //结果为显示NO         }         Object obj;         Employee employee = new Employee();         employee.RealName = "du";         employee.Birthday = DateTime.Now;         employee = o as Employee;         obj = o as Employee;                  if (employee != null)         {             //在if语句中使用e             MessageBox.Show(employee.RealName);         }         else         {             MessageBox.Show("no2");  //结果为显示NO2         }       }     /// <summary>     ///     /// </summary>     /// <param name="sender"></param>     /// <param name="e"></param>     private void button2_Click(object sender, EventArgs e)     {         var c1 = "";         var c2 = typeof(string);         object oc1 = c1;         object oc2 = c2;           var s1 = 0;         var s2 = '.';         object os1 = s1;         object os2 = s2;           bool b = false;           Stopwatch sw = Stopwatch.StartNew();         for (int i = 0; i < 10000000; i++)         {             b = c1.GetType() == typeof(string); // ~60ms             b = c1 is string; // ~60ms               b = c2.GetType() == typeof(string); // ~60ms             b = c2 is string; // ~50ms               b = oc1.GetType() == typeof(string); // ~60ms             b = oc1 is string; // ~68ms               b = oc2.GetType() == typeof(string); // ~60ms             b = oc2 is string; // ~64ms                 b = s1.GetType() == typeof(int); // ~130ms             b = s1 is int; // ~50ms               b = s2.GetType() == typeof(int); // ~140ms             b = s2 is int; // ~50ms               b = os1.GetType() == typeof(int); // ~60ms             b = os1 is int; // ~74ms               b = os2.GetType() == typeof(int); // ~60ms             b = os2 is int; // ~68ms                 b = GetType1<string, string>(c1); // ~178ms             b = GetType2<string, string>(c1); // ~94ms             b = Is<string, string>(c1); // ~70ms               b = GetType1<string, Type>(c2); // ~178ms             b = GetType2<string, Type>(c2); // ~96ms             b = Is<string, Type>(c2); // ~65ms               b = GetType1<string, object>(oc1); // ~190ms             b = Is<string, object>(oc1); // ~69ms               b = GetType1<string, object>(oc2); // ~180ms             b = Is<string, object>(oc2); // ~64ms                 b = GetType1<int, int>(s1); // ~230ms             b = GetType2<int, int>(s1); // ~75ms             b = Is<int, int>(s1); // ~136ms               b = GetType1<int, char>(s2); // ~238ms             b = GetType2<int, char>(s2); // ~69ms             b = Is<int, char>(s2); // ~142ms               b = GetType1<int, object>(os1); // ~178ms             b = Is<int, object>(os1); // ~69ms               b = GetType1<int, object>(os2); // ~178ms             b = Is<int, object>(os2); // ~69ms         }           sw.Stop();         MessageBox.Show(sw.Elapsed.TotalMilliseconds.ToString());     }     /// <summary>     ///     /// </summary>     /// <typeparam name="S"></typeparam>     /// <typeparam name="T"></typeparam>     /// <param name="t"></param>     /// <returns></returns>     static bool GetType1<S, T>(T t)     {         return t.GetType() == typeof(S);     }     /// <summary>     ///     /// </summary>     /// <typeparam name="S"></typeparam>     /// <typeparam name="T"></typeparam>     /// <param name="t"></param>     /// <returns></returns>     static bool GetType2<S, T>(T t)     {         return typeof(T) == typeof(S);     }     /// <summary>     ///     /// </summary>     /// <typeparam name="S"></typeparam>     /// <typeparam name="T"></typeparam>     /// <param name="t"></param>     /// <returns></returns>     static bool Is<S, T>(T t)     {         return t is S;     }     /// <summary>     ///     /// </summary>     /// <param name="sender"></param>     /// <param name="e"></param>     private void button3_Click(object sender, EventArgs e)     {         var cl1 = new Class1();         if (cl1 is IFormatProvider)         {             MessageBox.Show("cl1 is IFormatProvider ok");         }         else         {             MessageBox.Show("cl1 is IFormatProvider no");         }         if (cl1 is Object)         {             MessageBox.Show("cl1 is Object ok");         }         else         {             MessageBox.Show("cl1 is Object no");         }         if (cl1 is Class1)         {             MessageBox.Show("cl1 is Class1 ok");         }         else         {             MessageBox.Show("cl1 is Class1 no");         }         if (cl1 is Class2)         {             MessageBox.Show("cl1 is Class2 ok");         }         else         {             MessageBox.Show("cl1 is Class2 no");         }             var cl2 = new Class2();         if (cl2 is IFormatProvider)         {             MessageBox.Show("cl2 is IFormatProvider ok");         }         else         {             MessageBox.Show("cl2 is IFormatProvider no");         }         if (cl2 is Class2)         {             MessageBox.Show("cl2 is Class2 ok");         }         else         {             MessageBox.Show("cl2 is Class2 no");         }         if (cl2 is Class1)         {             MessageBox.Show("cl2 is Class1 ok");         }         else         {             MessageBox.Show("cl2 is Class1 no");         }              Class1 cl = cl2;         if (cl is Class1)         {             MessageBox.Show("cl is Class1 ok");         }         else         {             MessageBox.Show("cl is Class1 no");         };         if(cl is Class2)         {             MessageBox.Show("cl is Class2 ok");         }         else         {             MessageBox.Show("cl is Class2 no");         };           bool isc1 = (cl is Class1);         if (isc1)         {             MessageBox.Show("true");         }       }     /// <summary>     ///     /// </summary>     /// <param name="sender"></param>     /// <param name="e"></param>     private void button4_Click(object sender, EventArgs e)     {         Object o = new Person("Jane");         ShowValue(o);           o = new Dog("Alaskan Malamute");         ShowValue(o);           Employee em = new Employee();         em.RealName = "geovindu";         em.Birthday = DateTime.Now;         o =em;         ShowValue(o);     }     /// <summary>     ///     /// </summary>     /// <param name="o"></param>     public static void ShowValue(object o)     {         if (o is Person)         {             Person p = (Person)o;             MessageBox.Show(p.Name);         }         else if (o is Dog)         {             Dog d = (Dog)o;             MessageBox.Show(d.Breed);         }         else         {             MessageBox.Show("啥也不是");         }     }   } /// <summary> /// /// </summary> public class Class1 : IFormatProvider {     public object GetFormat(Type t)     {         if (t.Equals(this.GetType()))             return this;         return null;     } } /// <summary> /// /// </summary> public class Class2 : Class1 {     public int Value { get; set; } } /// <summary> /// 员工 /// </summary> public class Employee {         /// <summary>     /// 真名     /// </summary>     public string RealName { set; get; }           /// <summary>     /// 出生日期     /// </summary>     public DateTime Birthday { set; get; } } /// <summary> /// /// </summary> public struct Person {     public string Name { get; set; }       public Person(string name)         : this()     {         Name = name;     } } /// <summary> /// /// </summary> public struct Dog {     public string Breed { get; set; }       public Dog(string breedName)         : this()     {         Breed = breedName;     } }

　　

TypeInfo，PropertyInfo，MethodInfo，FieldInfo

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/// <summary> /// Geovin Du 涂聚文 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void button5_Click(object sender, EventArgs e) {     Int32 indent = 0;     // Display information about each assembly loading into this AppDomain.     foreach (Assembly b in AppDomain.CurrentDomain.GetAssemblies())     {         Display(indent, "Assembly: {0}", b);           // Display information about each module of this assembly.         foreach (Module m in b.GetModules(true))         {             Display(indent + 1, "Module: {0}", m.Name);         }           // Display information about each type exported from this assembly.           indent += 1;         foreach (Type t in b.GetExportedTypes())         {             Display(0, "");             Display(indent, "Type: {0}", t);               // For each type, show its members & their custom attributes.               indent += 1;             foreach (MemberInfo mi in t.GetMembers())             {                 Display(indent, "Member: {0}", mi.Name);                 DisplayAttributes(indent, mi);                   // If the member is a method, display information about its parameters.                   if (mi.MemberType == MemberTypes.Method)                 {                     foreach (ParameterInfo pi in ((MethodInfo)mi).GetParameters())                     {                         Display(indent + 1, "Parameter: Type={0}, Name={1}", pi.ParameterType, pi.Name);                     }                 }                   // If the member is a property, display information about the property's accessor methods.                 if (mi.MemberType == MemberTypes.Property)                 {                     foreach (MethodInfo am in ((PropertyInfo)mi).GetAccessors())                     {                         Display(indent + 1, "Accessor method: {0}", am);                     }                 }             }             indent -= 1;         }         indent -= 1;     } }     /// <summary> /// Displays the custom attributes applied to the specified member. /// </summary> /// <param name="indent"></param> /// <param name="mi"></param> public static void DisplayAttributes(Int32 indent, MemberInfo mi) {     // Get the set of custom attributes; if none exist, just return.     object[] attrs = mi.GetCustomAttributes(false);     if (attrs.Length == 0) { return; }       // Display the custom attributes applied to this member.     Display(indent + 1, "Attributes:");     foreach (object o in attrs)     {         Display(indent + 2, "{0}", o.ToString());     } } /// <summary> /// Display a formatted string indented by the specified amount. /// </summary> /// <param name="indent"></param> /// <param name="format"></param> /// <param name="param"></param> public static void Display(Int32 indent, string format, params object[] param) {     string st = new string(' ', indent * 2);     MessageBox.Show(st);     string s=string.Format("format:{0},param:{1}.",format, param);     MessageBox.Show(s); } /// <summary> /// /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void button6_Click(object sender, EventArgs e) {   // System.Reflection.MemberTypes     //4.6,4.5 .net     //TypeInfo t = typeof(Calendar).GetTypeInfo();     //4.6,4.5     // IEnumerable<PropertyInfo> pList = t.DeclaredProperties;     //4.5,4.6     //IEnumerable<MethodInfo> mList = t.DeclaredMethods;               //4.0     IEnumerable<PropertyInfo> pList = typeof(Calendar).GetProperties();     IEnumerable<MethodInfo> mList = typeof(Calendar).GetMethods();     IEnumerable<FieldInfo> fList = typeof(Calendar).GetFields();       StringBuilder sb = new StringBuilder();     sb.Append("Properties:");     foreach (PropertyInfo p in pList)     {           sb.Append("\n" + p.DeclaringType.Name + ": " + p.Name);     }     sb.Append("\nMethods:");     foreach (MethodInfo m in mList)     {         sb.Append("\n" + m.DeclaringType.Name + ": " + m.Name);     }     MessageBox.Show(sb.ToString()); }