📅 最后修改于: 2020-11-19 08:50:18 🧑 作者: Mango
在VB.Net中，可以将字符串用作字符数组，但是，更常见的做法是使用String关键字声明一个字符串变量。 字符串关键字是System.String类的别名。
您可以使用以下方法之一创建字符串对象-
通过将字符串字面量分配给String变量
通过使用String类构造函数
通过使用字符串串联运算符(+)
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
编译并执行上述代码后，将产生以下结果-
Full Name: Rowan Atkinson
Greetings: Hello
Message: Hello From Tutorials Point
Message: Message sent at 5:58 PM on Wednesday, December 12, 2012
String类具有以下两个属性-
| Sr.No | Property Name & Description |
|---|---|
| 1 |
Chars Gets the Char object at a specified position in the current String object. |
| 2 |
Length Gets the number of characters in the current String object. |
String类具有许多方法，可帮助您处理字符串对象。下表提供了一些最常用的方法-
| Sr.No | Method Name & Description |
|---|---|
| 1 |
Public Shared Function Compare ( strA As String, strB As String ) As Integer Compares two specified string objects and returns an integer that indicates their relative position in the sort order. |
| 2 |
Public Shared Function Compare ( strA As String, strB As String, ignoreCase As Boolean ) As Integer Compares two specified string objects and returns an integer that indicates their relative position in the sort order. However, it ignores case if the Boolean parameter is true. |
| 3 |
Public Shared Function Concat ( str0 As String, str1 As String ) As String Concatenates two string objects. |
| 4 |
Public Shared Function Concat ( str0 As String, str1 As String, str2 As String ) As String Concatenates three string objects. |
| 5 |
Public Shared Function Concat (str0 As String, str1 As String, str2 As String, str3 As String ) As String Concatenates four string objects. |
| 6 |
Public Function Contains ( value As String ) As Boolean Returns a value indicating whether the specified string object occurs within this string. |
| 7 |
Public Shared Function Copy ( str As String ) As String Creates a new String object with the same value as the specified string. |
| 8 |
pPublic Sub CopyTo ( sourceIndex As Integer, destination As Char(), destinationIndex As Integer, count As Integer ) Copies a specified number of characters from a specified position of the string object to a specified position in an array of Unicode characters. |
| 9 |
Public Function EndsWith ( value As String ) As Boolean Determines whether the end of the string object matches the specified string. |
| 10 |
Public Function Equals ( value As String ) As Boolean Determines whether the current string object and the specified string object have the same value. |
| 11 |
Public Shared Function Equals ( a As String, b As String ) As Boolean Determines whether two specified string objects have the same value. |
| 12 |
Public Shared Function Format ( format As String, arg0 As Object ) As String Replaces one or more format items in a specified string with the string representation of a specified object. |
| 13 |
Public Function IndexOf ( value As Char ) As Integer Returns the zero-based index of the first occurrence of the specified Unicode character in the current string. |
| 14 |
Public Function IndexOf ( value As String ) As Integer Returns the zero-based index of the first occurrence of the specified string in this instance. |
| 15 |
Public Function IndexOf ( value As Char, startIndex As Integer ) As Integer Returns the zero-based index of the first occurrence of the specified Unicode character in this string, starting search at the specified character position. |
| 16 |
Public Function IndexOf ( value As String, startIndex As Integer ) As Integer Returns the zero-based index of the first occurrence of the specified string in this instance, starting search at the specified character position. |
| 17 |
Public Function IndexOfAny ( anyOf As Char() ) As Integer Returns the zero-based index of the first occurrence in this instance of any character in a specified array of Unicode characters. |
| 18 |
Public Function IndexOfAny ( anyOf As Char(), startIndex As Integer ) As Integer Returns the zero-based index of the first occurrence in this instance of any character in a specified array of Unicode characters, starting search at the specified character position. |
| 19 |
Public Function Insert ( startIndex As Integer, value As String ) As String Returns a new string in which a specified string is inserted at a specified index position in the current string object. |
| 20 |
Public Shared Function IsNullOrEmpty ( value As String ) As Boolean Indicates whether the specified string is null or an Empty string. |
| 21 |
Public Shared Function Join ( separator As String, ParamArray value As String() ) As String Concatenates all the elements of a string array, using the specified separator between each element. |
| 22 |
Public Shared Function Join ( separator As String, value As String(), startIndex As Integer, count As Integer ) As String Concatenates the specified elements of a string array, using the specified separator between each element. |
| 23 |
Public Function LastIndexOf ( value As Char ) As Integer Returns the zero-based index position of the last occurrence of the specified Unicode character within the current string object. |
| 24 |
Public Function LastIndexOf ( value As String ) As Integer Returns the zero-based index position of the last occurrence of a specified string within the current string object. |
| 25 |
Public Function Remove ( startIndex As Integer ) As String Removes all the characters in the current instance, beginning at a specified position and continuing through the last position, and returns the string. |
| 26 |
Public Function Remove ( startIndex As Integer, count As Integer ) As String Removes the specified number of characters in the current string beginning at a specified position and returns the string. |
| 27 |
Public Function Replace ( oldChar As Char, newChar As Char ) As String Replaces all occurrences of a specified Unicode character in the current string object with the specified Unicode character and returns the new string. |
| 28 |
Public Function Replace ( oldValue As String, newValue As String ) As String Replaces all occurrences of a specified string in the current string object with the specified string and returns the new string. |
| 29 |
Public Function Split ( ParamArray separator As Char() ) As String() Returns a string array that contains the substrings in the current string object, delimited by elements of a specified Unicode character array. |
| 30 |
Public Function Split ( separator As Char(), count As Integer ) As String() Returns a string array that contains the substrings in the current string object, delimited by elements of a specified Unicode character array. The int parameter specifies the maximum number of substrings to return. |
| 31 |
Public Function StartsWith ( value As String ) As Boolean Determines whether the beginning of this string instance matches the specified string. |
| 32 |
Public Function ToCharArray As Char() Returns a Unicode character array with all the characters in the current string object. |
| 33 |
Public Function ToCharArray ( startIndex As Integer, length As Integer ) As Char() Returns a Unicode character array with all the characters in the current string object, starting from the specified index and up to the specified length. |
| 34 |
Public Function ToLower As String Returns a copy of this string converted to lowercase. |
| 35 |
Public Function ToUpper As String Returns a copy of this string converted to uppercase. |
| 36 |
Public Function Trim As String Removes all leading and trailing white-space characters from the current String object. |
上面的方法列表并不详尽，请访问MSDN库以获取方法和String类构造函数的完整列表。
以下示例演示了上述一些方法-
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
编译并执行上述代码后，将产生以下结果-
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
编译并执行上述代码后，将产生以下结果-
The sequence 'test' was found.
获取子字符串：
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
编译并执行上述代码后，将产生以下结果-
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
编译并执行上述代码后，将产生以下结果-
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