Csharp 简明教程

C

在 C# 中，可以使用字符串作为字符数组，然而，更常见的做法是使用 string 关键字来声明字符串变量。字符串关键字是 System.String 类的别名。

In C#, you can use strings as array of characters, However, more common practice is to use the string keyword to declare a string variable. The string keyword is an alias for the System.String class.

Creating a String Object

可以使用以下方法之一创建字符串对象 -

You can create string object using one of the following methods −

By assigning a string literal to a String variable
By using a String class constructor
By using the string concatenation operator (+)
By retrieving a property or calling a method that returns a string
By calling a formatting method to convert a value or an object to its string representation

以下示例演示了这一点−

The following example demonstrates this −

using System;

namespace StringApplication {

   class Program {

      static void Main(string[] args) {
         //from string literal and string concatenation
         string fname, lname;
         fname = "Rowan";
         lname = "Atkinson";

         char []letters= { 'H', 'e', 'l', 'l','o' };
         string [] sarray={ "Hello", "From", "Tutorials", "Point" };

         string fullname = fname + lname;
         Console.WriteLine("Full Name: {0}", fullname);

         //by using string constructor { 'H', 'e', 'l', 'l','o' };
         string greetings = new string(letters);
         Console.WriteLine("Greetings: {0}", greetings);

         //methods returning string { "Hello", "From", "Tutorials", "Point" };
         string message = String.Join(" ", sarray);
         Console.WriteLine("Message: {0}", message);

         //formatting method to convert a value
         DateTime waiting = new DateTime(2012, 10, 10, 17, 58, 1);
         string chat = String.Format("Message sent at {0:t} on {0:D}", waiting);
         Console.WriteLine("Message: {0}", chat);
      }
   }
}

编译并执行上述代码后，将产生以下结果 −

When the above code is compiled and executed, it produces the following result −

Full Name: RowanAtkinson
Greetings: Hello
Message: Hello From Tutorials Point
Message: Message sent at 5:58 PM on Wednesday, October 10, 2012

Properties of the String Class

String 类具有以下两个属性 -

The String class has the following two properties −

Sr.No.

Property & Description

Chars Gets the Char object at a specified position in the current String object.

Length Gets the number of characters in the current String object.

Methods of the String Class

String 类有许多方法可帮助使用字符串对象。下表列出了一些最常用的方法 -

The String class has numerous methods that help you in working with the string objects. The following table provides some of the most commonly used methods −

有关方法和字符串类构造函数的完整列表，请访问 MSDN 库。

You can visit MSDN library for the complete list of methods and String class constructors.

Examples

以下示例演示了一些上面提到的方法 -

The following example demonstrates some of the methods mentioned above −

Comparing Strings

using System;

namespace StringApplication {

   class StringProg {

      static void Main(string[] args) {
         string str1 = "This is test";
         string str2 = "This is text";

         if (String.Compare(str1, str2) == 0) {
            Console.WriteLine(str1 + " and " + str2 +  " are equal.");
         } else {
            Console.WriteLine(str1 + " and " + str2 + " are not equal.");
         }
         Console.ReadKey() ;
      }
   }
}

编译并执行上述代码后，将产生以下结果 −

When the above code is compiled and executed, it produces the following result −

This is test and This is text are not equal.

String Contains String

using System;

namespace StringApplication {

   class StringProg {

      static void Main(string[] args) {
         string str = "This is test";

         if (str.Contains("test")) {
            Console.WriteLine("The sequence 'test' was found.");
         }
         Console.ReadKey() ;
      }
   }
}

编译并执行上述代码后，将产生以下结果 −

When the above code is compiled and executed, it produces the following result −

The sequence 'test' was found.

Getting a Substring

using System;

namespace StringApplication {

   class StringProg {

      static void Main(string[] args) {
         string str = "Last night I dreamt of San Pedro";
         Console.WriteLine(str);
         string substr = str.Substring(23);
         Console.WriteLine(substr);
      }
   }
}

编译并执行上述代码后，将产生以下结果 −

When the above code is compiled and executed, it produces the following result −

San Pedro

Joining Strings

using System;

namespace StringApplication {

   class StringProg {

      static void Main(string[] args) {
         string[] starray = new string[]{"Down the way nights are dark",
            "And the sun shines daily on the mountain top",
            "I took a trip on a sailing ship",
            "And when I reached Jamaica",
            "I made a stop"};

         string str = String.Join("\n", starray);
         Console.WriteLine(str);
      }
   }
}

编译并执行上述代码后，将产生以下结果 −

When the above code is compiled and executed, it produces the following result −

Down the way nights are dark
And the sun shines daily on the mountain top
I took a trip on a sailing ship
And when I reached Jamaica
I made a stop