chap17.lst

Csharp2完全参考手册源代码 详细的说明可以在书里看到 该书是08年刚出炉很新鲜

listing 1
// Demonstrate is. 
 
using System; 
 
class A {} 
class B : A {} 
 
class UseIs { 
  public static void Main() { 
    A a = new A(); 
    B b = new B(); 
 
    if(a is A) Console.WriteLine("a is an A"); 
    if(b is A)  
      Console.WriteLine("b is an A because it is derived from A"); 
    if(a is B)  
      Console.WriteLine("This won't display -- a not derived from B"); 
 
    if(b is B) Console.WriteLine("B is a B"); 
    if(a is object) Console.WriteLine("a is an object"); 
  } 
}

listing 2
// Use is to avoid an invalid cast. 
 
using System; 
 
class A {} 
class B : A {} 
 
class CheckCast { 
  public static void Main() { 
    A a = new A(); 
    B b = new B(); 
 
    // Check to see if a can be cast to B. 
    if(a is B)  // if so, do the cast 
      b = (B) a; 
    else // if not, skip the cast 
      b = null; 
 
    if(b==null)  
      Console.WriteLine("Cast b = (B) a is NOT allowed."); 
    else 
      Console.WriteLine("Cast b = (B) a is allowed"); 
  } 
}

listing 3
// Demonstrate as. 
 
using System; 
 
class A {} 
class B : A {} 
 
class CheckCast { 
  public static void Main() { 
    A a = new A(); 
    B b = new B(); 
 
    b = a as B; // cast, if possible 
 
    if(b==null)  
      Console.WriteLine("Cast b = (B) a is NOT allowed."); 
    else 
      Console.WriteLine("Cast b = (B) a is allowed"); 
  } 
}

listing 4
// Demonstrate typeof. 
 
using System; 
using System.IO; 
 
class UseTypeof { 
  public static void Main() { 
    Type t = typeof(StreamReader); 
 
    Console.WriteLine(t.FullName);     
 
    if(t.IsClass) Console.WriteLine("Is a class."); 
    if(t.IsAbstract) Console.WriteLine("Is abstract."); 
    else Console.WriteLine("Is concrete."); 
 
  } 
}

listing 5
// Analyze methods using reflection. 
 
using System; 
using System.Reflection; 
 
class MyClass { 
  int x; 
  int y; 
 
  public MyClass(int i, int j) { 
    x = i; 
    y = j; 
  } 
 
  public int sum() { 
    return x+y; 
  } 
 
  public bool isBetween(int i) { 
    if(x < i && i < y) return true; 
    else return false; 
  } 
 
  public void set(int a, int b) { 
    x = a; 
    y = b; 
  } 
 
  public void set(double a, double b) { 
    x = (int) a; 
    y = (int) b; 
  } 
 
  public void show() { 
    Console.WriteLine(" x: {0}, y: {1}", x, y); 
  } 
} 
 
class ReflectDemo { 
  public static void Main() { 
    Type t = typeof(MyClass); // get a Type object representing MyClass 
 
    Console.WriteLine("Analyzing methods in " + t.Name);     
    Console.WriteLine(); 
 
    Console.WriteLine("Methods supported: "); 
 
    MethodInfo[] mi = t.GetMethods(); 
 
    // Display methods supported by MyClass. 
    foreach(MethodInfo m in mi) { 
      // Display return type and name. 
      Console.Write("   " + m.ReturnType.Name + 
                      " " + m.Name + "("); 
 
      // Display parameters. 
      ParameterInfo[] pi = m.GetParameters(); 
 
      for(int i=0; i < pi.Length; i++) { 
        Console.Write(pi[i].ParameterType.Name + 
                      " " + pi[i].Name); 
        if(i+1 < pi.Length) Console.Write(", "); 
      } 
 
      Console.WriteLine(")"); 
     
      Console.WriteLine(); 
    } 
  } 
}

listing 6
// Invoke methods using reflection. 
 
using System; 
using System.Reflection; 
 
class MyClass { 
  int x; 
  int y; 
 
  public MyClass(int i, int j) { 
    x = i; 
    y = j; 
  } 
 
  public int sum() { 
    return x+y; 
  } 
 
  public bool isBetween(int i) { 
    if((x < i) && (i < y)) return true; 
    else return false; 
  } 
 
  public void set(int a, int b) { 
    Console.Write("Inside set(int, int). "); 
    x = a; 
    y = b; 
    show(); 
  } 
 
  // Overload set. 
  public void set(double a, double b) { 
    Console.Write("Inside set(double, double). "); 
    x = (int) a; 
    y = (int) b; 
    show(); 
  } 
 
  public void show() { 
    Console.WriteLine("Values are x: {0}, y: {1}", x, y); 
  } 
} 
 
class InvokeMethDemo { 
  public static void Main() { 
    Type t = typeof(MyClass);   
    MyClass reflectOb = new MyClass(10, 20); 
    int val; 
 
    Console.WriteLine("Invoking methods in " + t.Name);     
    Console.WriteLine(); 
    MethodInfo[] mi = t.GetMethods(); 
 
    // Invoke each method. 
    foreach(MethodInfo m in mi) { 
      // Get the parameters. 
      ParameterInfo[] pi = m.GetParameters(); 
 
      if(m.Name.CompareTo("set")==0 && 
         pi[0].ParameterType == typeof(int)) { 
        object[] args = new object[2]; 
        args[0] = 9; 
        args[1] = 18; 
        m.Invoke(reflectOb, args); 
      } 
      else if(m.Name.CompareTo("set")==0 && 
         pi[0].ParameterType == typeof(double)) { 
        object[] args = new object[2]; 
        args[0] = 1.12; 
        args[1] = 23.4; 
        m.Invoke(reflectOb, args); 
      } 
      else if(m.Name.CompareTo("sum")==0) { 
        val = (int) m.Invoke(reflectOb, null); 
        Console.WriteLine("sum is " + val); 
      } 
      else if(m.Name.CompareTo("isBetween")==0) { 
        object[] args = new object[1]; 
        args[0] = 14; 
        if((bool) m.Invoke(reflectOb, args)) 
          Console.WriteLine("14 is between x and y"); 
      } 
      else if(m.Name.CompareTo("show")==0) { 
        m.Invoke(reflectOb, null); 
      } 
    } 
  } 
}

listing 7
// Create an object using reflection. 
 
using System; 
using System.Reflection; 
 
class MyClass { 
  int x; 
  int y; 
 
  public MyClass(int i) { 
    Console.WriteLine("Constructing MyClass(int, int). "); 
    x = y = i;  
  } 
 
  public MyClass(int i, int j) { 
    Console.WriteLine("Constructing MyClass(int, int). "); 
    x = i; 
    y = j; 
    show(); 
  } 
 
  public int sum() { 
    return x+y; 
  } 
 
  public bool isBetween(int i) { 
    if((x < i) && (i < y)) return true; 
    else return false; 
  } 
 
  public void set(int a, int b) { 
    Console.Write("Inside set(int, int). "); 
    x = a; 
    y = b; 
    show(); 
  } 
 
  // Overload set. 
  public void set(double a, double b) { 
    Console.Write("Inside set(double, double). "); 
    x = (int) a; 
    y = (int) b; 
    show(); 
  } 
 
  public void show() { 
    Console.WriteLine("Values are x: {0}, y: {1}", x, y); 
  } 
 
} 
 
class InvokeConsDemo { 
  public static void Main() { 
    Type t = typeof(MyClass); 
    int val; 
 
    // Get constructor info. 
    ConstructorInfo[] ci = t.GetConstructors(); 
 
    Console.WriteLine("Available constructors: "); 
    foreach(ConstructorInfo c in ci) { 
      // Display return type and name. 
      Console.Write("   " + t.Name + "("); 
 
      // Display parameters. 
      ParameterInfo[] pi = c.GetParameters(); 
 
      for(int i=0; i < pi.Length; i++) { 
        Console.Write(pi[i].ParameterType.Name + 
                      " " + pi[i].Name); 
        if(i+1 < pi.Length) Console.Write(", "); 
      } 
 
      Console.WriteLine(")"); 
    } 
    Console.WriteLine(); 
 
    // Find matching constructor. 
    int x; 
 
    for(x=0; x < ci.Length; x++) { 
      ParameterInfo[] pi =  ci[x].GetParameters(); 
      if(pi.Length == 2) break; 
    } 
 
    if(x == ci.Length) { 
      Console.WriteLine("No matching constructor found."); 
      return; 
    } 
    else 
      Console.WriteLine("Two-parameter constructor found.\n"); 
 
    // Construct the object.   
    object[] consargs = new object[2]; 
    consargs[0] = 10; 
    consargs[1] = 20; 
    object reflectOb = ci[x].Invoke(consargs); 
 
    Console.WriteLine("\nInvoking methods on reflectOb."); 
    Console.WriteLine(); 
    MethodInfo[] mi = t.GetMethods(); 
 
    // Invoke each method. 
    foreach(MethodInfo m in mi) { 
      // Get the parameters. 
      ParameterInfo[] pi = m.GetParameters(); 
 
      if(m.Name.CompareTo("set")==0 && 
         pi[0].ParameterType == typeof(int)) { 
        // This is set(int, int). 
        object[] args = new object[2]; 
        args[0] = 9; 
        args[1] = 18; 
        m.Invoke(reflectOb, args); 
      } 
      else if(m.Name.CompareTo("set")==0 && 
              pi[0].ParameterType == typeof(double)) { 
        // This is set(double, double). 
        object[] args = new object[2]; 
        args[0] = 1.12; 
        args[1] = 23.4; 
        m.Invoke(reflectOb, args); 
      } 
      else if(m.Name.CompareTo("sum")==0) { 
        val = (int) m.Invoke(reflectOb, null); 
        Console.WriteLine("sum is " + val); 
      } 
      else if(m.Name.CompareTo("isBetween")==0) { 
        object[] args = new object[1]; 
        args[0] = 14; 
        if((bool) m.Invoke(reflectOb, args)) 
          Console.WriteLine("14 is between x and y"); 
      } 
      else if(m.Name.CompareTo("show")==0) { 
        m.Invoke(reflectOb, null); 
      } 
    } 
  } 
}

listing 8
// A file that contains three classes.  Call this file MyClasses.cs. 
 
using System; 
 
class MyClass { 
  int x; 
  int y; 
 
  public MyClass(int i) { 
    Console.WriteLine("Constructing MyClass(int). "); 
    x = y = i;  
    show(); 
  } 
 
  public MyClass(int i, int j) { 
    Console.WriteLine("Constructing MyClass(int, int). "); 
    x = i; 
    y = j; 
    show(); 
  } 
 
  public int sum() { 
    return x+y; 
  } 
 
  public bool isBetween(int i) { 
    if((x < i) && (i < y)) return true; 
    else return false; 
  } 
 
  public void set(int a, int b) { 
    Console.Write("Inside set(int, int). "); 
    x = a; 
    y = b; 
    show(); 
  } 
 
  // Overload set. 
  public void set(double a, double b) { 
    Console.Write("Inside set(double, double). "); 
    x = (int) a; 
    y = (int) b; 
    show(); 
  } 
 
  public void show() { 
    Console.WriteLine("Values are x: {0}, y: {1}", x, y); 
  } 
} 
 
class AnotherClass { 
  string remark; 
 
  public AnotherClass(string str) { 
    remark = str; 
  } 
 
  public void show() { 
    Console.WriteLine(remark); 
  } 
} 
 
class Demo { 
  public static void Main() { 
    Console.WriteLine("This is a placeholder."); 
  } 
}

listing 9
/* Locate an assembly, determine types, and create