Visual Basic 字符串

在 VB 中，可以使用字符串作为字符数组，但更常见的做法是使用 String 关键字来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

可以使用以下方法之一创建字符串对象:

• 通过将一个字符串文字分配给一个 String
• 变量通过使用一个 String 类的构造函数
• 通过使用字符串连接运算符 (+)
• 通过检索一个属性或调用返回一个字符串的方法
• 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

下面的实例演示了如何创建对象:

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

String 类的属性

String 类具有以下两个属性:

String 类的方法

String 类有许多方法可以用来处理 String 对象。下面列表提供了一些最常用的方法:

上面的方法列表并不详尽，可以请访问 MSDN 库以获取完整的方法列表和 String 类的构造方法。

实例

以下实例演示了上面提到的一些方法:

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

结果如下:

This is test and This is text are not equal.

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

结果如下:

The sequence 'test' was found.

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

结果如下:

Last night I dreamt of San Pedro San Pedro.

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

结果如下:

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