委托-C#

1.Action委托:无返回值，但可以有参数。注：不用显示定义委托，参考https://msdn.microsoft.com/zh-cn/library/dd269635(v=vs.110).aspx

 1 using System;
 2 using System.IO;
 3 
 4 delegate void ConcatStrings(string string1, string string2);
 5 
 6 public class TestDelegate
 7 {
 8    public static void Main()
 9    {
10       string message1 = "The first line of a message.";
11       string message2 = "The second line of a message.";
12       ConcatStrings concat;
13 
14       if (Environment.GetCommandLineArgs().Length > 1)
15          concat = WriteToFile;
16       else
17          concat = WriteToConsole;
18 
19       concat(message1, message2);
20    }
21 
22    private static void WriteToConsole(string string1, string string2)
23    {
24       Console.WriteLine("{0}\n{1}", string1, string2);            
25    }
26 
27    private static void WriteToFile(string string1, string string2)
28    {
29       StreamWriter writer = null;  
30       try
31       {
32          writer = new StreamWriter(Environment.GetCommandLineArgs()[1], false);
33          writer.WriteLine("{0}\n{1}", string1, string2);
34       }
35       catch
36       {
37          Console.WriteLine("File write operation failed...");
38       }
39       finally
40       {
41          if (writer != null) writer.Close();
42       }      
43    }
44 }

delegate

 1 using System;
 2 using System.IO;
 3 
 4 public class TestAction2
 5 {
 6    public static void Main()
 7    {
 8       string message1 = "The first line of a message.";
 9       string message2 = "The second line of a message.";
10       Action<string, string> concat;
11 
12       if (Environment.GetCommandLineArgs().Length > 1)
13          concat = WriteToFile;
14       else
15          concat = WriteToConsole;
16 
17       concat(message1, message2);
18    }
19 
20    private static void WriteToConsole(string string1, string string2)
21    {
22       Console.WriteLine("{0}\n{1}", string1, string2);            
23    }
24 
25    private static void WriteToFile(string string1, string string2)
26    {
27       StreamWriter writer = null;  
28       try
29       {
30          writer = new StreamWriter(Environment.GetCommandLineArgs()[1], false);
31          writer.WriteLine("{0}\n{1}", string1, string2);
32       }
33       catch
34       {
35          Console.WriteLine("File write operation failed...");
36       }
37       finally
38       {
39          if (writer != null) writer.Close();
40       }      
41    }
42 }

Action

 1 using System;
 2 using System.IO;
 3 
 4 public class TestAnonymousMethod
 5 {
 6    public static void Main()
 7    {
 8       string message1 = "The first line of a message.";
 9       string message2 = "The second line of a message.";
10       Action<string, string> concat;
11 
12       if (Environment.GetCommandLineArgs().Length > 1)
13          concat = delegate(string s1, string s2) { WriteToFile(s1, s2); };
14       else
15          concat = delegate(string s1, string s2) { WriteToConsole(s1, s2);} ;
16 
17       concat(message1, message2);
18    }
19 
20    private static void WriteToConsole(string string1, string string2)
21    {
22       Console.WriteLine("{0}\n{1}", string1, string2);            
23    }
24 
25    private static void WriteToFile(string string1, string string2)
26    {
27       StreamWriter writer = null;  
28       try
29       {
30          writer = new StreamWriter(Environment.GetCommandLineArgs()[1], false);
31          writer.WriteLine("{0}\n{1}", string1, string2);
32       }
33       catch
34       {
35          Console.WriteLine("File write operation failed...");
36       }
37       finally
38       {
39          if (writer != null) writer.Close();
40       }      
41    }
42 }

Action和匿名方法

 1 using System;
 2 using System.IO;
 3 
 4 public class TestLambdaExpression
 5 {
 6    public static void Main()
 7    {
 8       string message1 = "The first line of a message.";
 9       string message2 = "The second line of a message.";
10       Action<string, string> concat;
11 
12       if (Environment.GetCommandLineArgs().Length > 1)
13          concat = (s1, s2) => WriteToFile(s1, s2);
14       else
15          concat = (s1, s2) => WriteToConsole(s1, s2);
16 
17       concat(message1, message2);
18    }
19 
20    private static void WriteToConsole(string string1, string string2)
21    {
22       Console.WriteLine("{0}\n{1}", string1, string2);            
23    }
24 
25    private static void WriteToFile(string string1, string string2)
26    {
27       StreamWriter writer = null;  
28       try
29       {
30          writer = new StreamWriter(Environment.GetCommandLineArgs()[1], false);
31          writer.WriteLine("{0}\n{1}", string1, string2);
32       }
33       catch
34       {
35          Console.WriteLine("File write operation failed...");
36       }
37       finally
38       {
39          if (writer != null) writer.Close();
40       }      
41    }
42 }

Action和Lambda表达式

2.Func：必有返回值，可以一个或者多个参数，注不用显示定义委托，来源于https://msdn.microsoft.com/zh-cn/library/bb534647(v=vs.110).aspx

 1 using System;
 2 
 3 delegate string[] ExtractMethod(string stringToManipulate, int maximum);
 4 
 5 public class DelegateExample
 6 {
 7    public static void Main()
 8    {
 9       // Instantiate delegate to reference ExtractWords method
10       ExtractMethod extractMeth = ExtractWords;
11       string title = "The Scarlet Letter";
12       // Use delegate instance to call ExtractWords method and display result
13       foreach (string word in extractMeth(title, 5))
14          Console.WriteLine(word);
15    }
16 
17    private static string[] ExtractWords(string phrase, int limit)
18    {
19       char[] delimiters = new char[] {' '};
20       if (limit > 0)
21          return phrase.Split(delimiters, limit);
22       else
23          return phrase.Split(delimiters);
24    }
25 }

delegate-Func

 1 using System;
 2 
 3 public class GenericFunc
 4 {
 5    public static void Main()
 6    {
 7       // Instantiate delegate to reference ExtractWords method
 8       Func<string, int, string[]> extractMethod = ExtractWords;
 9       string title = "The Scarlet Letter";
10       // Use delegate instance to call ExtractWords method and display result
11       foreach (string word in extractMethod(title, 5))
12          Console.WriteLine(word);
13    }
14 
15    private static string[] ExtractWords(string phrase, int limit)
16    {
17       char[] delimiters = new char[] {' '};
18       if (limit > 0)
19          return phrase.Split(delimiters, limit);
20       else
21          return phrase.Split(delimiters);
22    }
23 }

Func

 1 using System;
 2 
 3 public class LambdaExpression
 4 {
 5    public static void Main()
 6    {
 7       char[] separators = new char[] {' '};
 8       Func<string, int, string[]> extract = (s, i) => 
 9            i > 0 ? s.Split(separators, i) : s.Split(separators) ;
10 
11       string title = "The Scarlet Letter";
12       // Use Func instance to call ExtractWords method and display result
13       foreach (string word in extract(title, 5))
14          Console.WriteLine(word);
15    }
16 }
17 
18 
19 using System;
20 using System.Collections.Generic;
21 using System.Linq;
22 
23 public class Func3Example
24 {
25    public static void Main()
26    {
27       Func<String, int, bool> predicate = (str, index) => str.Length == index;
28 
29       String[] words = { "orange", "apple", "Article", "elephant", "star", "and" };
30       IEnumerable<String> aWords = words.Where(predicate).Select(str => str);
31 
32       foreach (String word in aWords)
33          Console.WriteLine(word);
34    }
35 }

Func和Lambda表达式

3.Delegate: 可以有参数，也可以有返回值。表示委托，委托是一种数据结构，它引用静态方法或引用类实例及该类的实例方法。来源于https://msdn.microsoft.com/zh-cn/library/system.delegate(v=vs.110).aspx

 1 using System;
 2 public class SamplesDelegate  {
 3 
 4    // Declares a delegate for a method that takes in an int and returns a String.
 5    public delegate String myMethodDelegate( int myInt );
 6 
 7    // Defines some methods to which the delegate can point.
 8    public class mySampleClass  {
 9 
10       // Defines an instance method.
11       public String myStringMethod ( int myInt )  {
12          if ( myInt > 0 )
13             return( "positive" );
14          if ( myInt < 0 )
15             return( "negative" );
16          return ( "zero" );
17       }
18 
19       // Defines a static method.
20       public static String mySignMethod ( int myInt )  {
21          if ( myInt > 0 )
22             return( "+" );
23          if ( myInt < 0 )
24             return( "-" );
25          return ( "" );
26       }
27    }
28 
29    public static void Main()  {
30 
31       // Creates one delegate for each method. For the instance method, an
32       // instance (mySC) must be supplied. For the static method, use the
33       // class name.
34       mySampleClass mySC = new mySampleClass();
35       myMethodDelegate myD1 = new myMethodDelegate( mySC.myStringMethod );
36       myMethodDelegate myD2 = new myMethodDelegate( mySampleClass.mySignMethod );
37 
38       // Invokes the delegates.
39       Console.WriteLine( "{0} is {1}; use the sign \"{2}\".", 5, myD1( 5 ), myD2( 5 ) );
40       Console.WriteLine( "{0} is {1}; use the sign \"{2}\".", -3, myD1( -3 ), myD2( -3 ) );
41       Console.WriteLine( "{0} is {1}; use the sign \"{2}\".", 0, myD1( 0 ), myD2( 0 ) );
42    }
43 
44 }

Delegate使用

4.EventHandler:表示将处理不包含事件数据的事件的方法。来源于https://msdn.microsoft.com/zh-cn/library/system.eventhandler(v=vs.110).aspx

 1 using System;
 2 
 3 namespace ConsoleApplication1
 4 {
 5     class Program
 6     {
 7         static void Main(string[] args)
 8         {
 9             Counter c = new Counter(new Random().Next(10));
10             c.ThresholdReached += c_ThresholdReached;
11 
12             Console.WriteLine("press 'a' key to increase total");
13             while (Console.ReadKey(true).KeyChar == 'a')
14             {
15                 Console.WriteLine("adding one");
16                 c.Add(1);
17             }
18         }
19 
20         static void c_ThresholdReached(object sender, ThresholdReachedEventArgs e)
21         {
22             Console.WriteLine("The threshold of {0} was reached at {1}.", e.Threshold,  e.TimeReached);
23             Environment.Exit(0);
24         }
25     }
26 
27     class Counter
28     {
29         private int threshold;
30         private int total;
31 
32         public Counter(int passedThreshold)
33         {
34             threshold = passedThreshold;
35         }
36 
37         public void Add(int x)
38         {
39             total += x;
40             if (total >= threshold)
41             {
42                 ThresholdReachedEventArgs args = new ThresholdReachedEventArgs();
43                 args.Threshold = threshold;
44                 args.TimeReached = DateTime.Now;
45                 OnThresholdReached(args);
46             }
47         }
48 
49         protected virtual void OnThresholdReached(ThresholdReachedEventArgs e)
50         {
51             EventHandler<ThresholdReachedEventArgs> handler = ThresholdReached;
52             if (handler != null)
53             {
54                 handler(this, e);
55             }
56         }
57 
58         public event EventHandler<ThresholdReachedEventArgs> ThresholdReached;
59     }
60 
61     public class ThresholdReachedEventArgs : EventArgs
62     {
63         public int Threshold { get; set; }
64         public DateTime TimeReached { get; set; }
65     }
66 }

EventHandler

posted on 2015-07-20 10:45 魔天天阅读(114) 评论(0) 编辑收藏举报