// A simple delegate example.
using System;
// Declare a delegate.
delegate string strMod(string str);
class DelegateTest {
// Replaces spaces with hyphens.
static string replaceSpaces(string a) {
Console.WriteLine("Replaces spaces with hyphens.");
return a.Replace(' ', '-');
}
// Remove spaces.
static string removeSpaces(string a) {
string temp = "";
int i;
Console.WriteLine("Removing spaces.");
for(i=0; i < a.Length; i++)
if(a[i] != ' ') temp += a[i];
return temp;
}
// Reverse a string.
static string reverse(string a) {
string temp = "";
int i, j;
Console.WriteLine("Reversing string.");
for(j=0, i=a.Length-1; i >= 0; i--, j++)
temp += a[i];
return temp;
}
public static void Main() {
// Construct a delegate.
strMod strOp = new strMod(replaceSpaces);
string str;
/*
注意這邊，replaceSpaces這個function被當成strMod的參數傳進來，
這樣就完成委派，之後對strOp傳參數進去，就等同於對replaceSpaces傳參數
*/
// Call methods through the delegate.
str = strOp("This is a test.");
/*
所以當strOp在這邊傳入This is a test.的時候，相當於replaceSpaces("This is a test.")
會輸出 Resulting string: This-is-a-test.
*/
Console.WriteLine("Resulting string: " + str);
Console.WriteLine();
strOp = new strMod(removeSpaces);
/* 現在又改註冊removeSpaces這個function */
str = strOp("This is a test.");
Console.WriteLine("Resulting string: " + str);
/* 會輸出 Resulting string: Thisisatest. */
Console.WriteLine();
strOp = new strMod(reverse);
str = strOp("This is a test.");
Console.WriteLine("Resulting string: " + str);
}
}
The output from the program is shown here:
Replaces spaces with hyphens.
Resulting string: This-is-a-test.
Removing spaces.
Resulting string: Thisisatest.
Reversing string.
Resulting string: .tset a si sihT
參考書目
C#: The Complete Reference
by Herbert Schildt
McGraw-Hill/Osborne © 2002 (933 pages) Citation
ISBN:9780072134858
Learn all aspects of the C# programming language that support the .NET Framework with this all-inclusive guide.
chapter 15 : Delegates and Events
