VB.Net - 字符串

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在 VB.Net 中，您可以将字符串用作字符数组，但是，更常见的做法是使用 String 关键字来声明字符串变量。string 关键字是System.String类的别名。

创建字符串对象

您可以使用以下方法之一创建字符串对象 -

• 通过将字符串文字分配给字符串变量

• 通过使用 String 类构造函数

• 通过使用字符串连接运算符 (+)

• 通过检索属性或调用返回字符串的方法

• 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

以下示例演示了这一点 -

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

当上面的代码被编译并执行时，它会产生以下结果 -

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 类具有以下两个属性 -

String 类的方法

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

上面的方法列表并不详尽，请访问 MSDN 库以获取完整的方法列表和 String 类构造函数。

例子

以下示例演示了上面提到的一些方法 -

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

当上面的代码被编译并执行时，它会产生以下结果 -

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

当上面的代码被编译并执行时，它会产生以下结果 -

The sequence 'test' was found.

获取子串：

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

当上面的代码被编译并执行时，它会产生以下结果 -

Last night I dreamt of San Pedro
San Pedro.

连接字符串

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

当上面的代码被编译并执行时，它会产生以下结果 -

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