字符串

VB.Net - 字符串

在VB.Net中，可以使用字符串作为字符数组，但是更常见的做法是使用String关键字声明一个字符串变量。 string关键字是System.String类的别名。

创建一个字符串对象 您可以使用以下方法之一创建字符串对象：

• By assigning a string literal to a String variable 通过指定一个字符串给一个字符串变量

• By using a String class constructor 通过使用String类构造函数

• By using the string concatenation operator (+) 通过使用字符串连接运算符（+）

• By retrieving a property or calling a method that returns a string 通过检索属性或调用返回字符串的方法

• By calling a formatting method to convert a value or object to its string representation 通过调用格式化方法将值或对象转换为其字符串表示形式

下面的例子说明了这一点：

Module strings
   Sub Main()
      Dim fname, lname, fullname, greetings As String
      fname = "Rowan"
      lname = "Atkinson"
      fullname = fname + " " + lname
      Console.WriteLine("Full Name: {0}", fullname)

     'by using string constructor
      Dim letters As Char() = {"H", "e", "l", "l", "o"}
      greetings = New String(letters)
      Console.WriteLine("Greetings: {0}", greetings)

      'methods returning String
      Dim sarray() As String = {"Hello", "From", "Tutorials", "Point"}
      Dim message As String = String.Join(" ", sarray)
      Console.WriteLine("Message: {0}", message)

      'formatting method to convert a value 
      Dim waiting As DateTime = New DateTime(2012, 12, 12, 17, 58, 1)
      Dim chat As String = String.Format("Message sent at {0:t} on {0:D}", waiting)
      Console.WriteLine("Message: {0}", chat)
      Console.ReadLine()
   End Sub
End Module

当上述代码被编译和执行时，它产生了以下结果：

Full Name: Rowan Atkinson
Greetings: Hello
Message: Hello From Tutorials Point
Message: Message sent at 5:58 PM on Wednesday, December 12, 2012

String类的属性

String类有以下两个属性：

String类的方法

String类有许多方法可以帮助你处理字符串对象。 下表提供了一些最常用的方法：

从当前String对象中删除所有前导和尾部空格字符。

上面列出的方法并不详尽，请访问MSDN库获取完整的方法列表和String类构造函数。

例子：

下面的例子说明了上述一些方法：

比较字符串：

Module strings
   Sub Main()
      Dim str1, str2 As String
      str1 = "This is test"
      str2 = "This is text"
      If (String.Compare(str1, str2) = 0) Then
          Console.WriteLine(str1 + " and " + str2 +
                            " are equal.")
      Else
          Console.WriteLine(str1 + " and " + str2 +
                            " are not equal.")
      End If
      Console.ReadLine()
   End Sub
End Module

当上述代码被编译和执行时，它产生了以下结果：

This is test and This is text are not equal.

字符串包含字符串：

Module strings
   Sub Main()
      Dim str1 As String
      str1 = "This is test"
      If (str1.Contains("test")) Then
          Console.WriteLine("The sequence 'test' was found.")
      End If
      Console.ReadLine()
   End Sub
End Module

当上述代码被编译和执行时，它产生了以下结果：

The sequence 'test' was found.

获取的子字符串：

Module strings
   Sub Main()
      Dim str As String
      str = "Last night I dreamt of San Pedro"
      Console.WriteLine(str)
      Dim substr As String = str.Substring(23)
      Console.WriteLine(substr)
      Console.ReadLine()
   End Sub
End Module

当上述代码被编译和执行时，它产生了以下结果：

Last night I dreamt of San Pedro
San Pedro.

加入字符串：

Module strings
   Sub Main()
      Dim strarray As String() = {"Down the way where the nights are gay",
                          "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"}
      Dim str As String = String.Join(vbCrLf, strarray)
      Console.WriteLine(str)
      Console.ReadLine()
   End Sub
End Module

当上述代码被编译和执行时，它产生了以下结果：

Down the way where the nights are gay
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