String.IsNullOrWhiteSpace(String) 方法
定义
指示指定的字符串是 null、空还是仅由空白字符组成。Indicates whether a specified string is null, empty, or consists only of white-space characters.
public:
static bool IsNullOrWhiteSpace(System::String ^ value);
public static bool IsNullOrWhiteSpace (string value);
public static bool IsNullOrWhiteSpace (string? value);
static member IsNullOrWhiteSpace : string -> bool
Public Shared Function IsNullOrWhiteSpace (value As String) As Boolean
参数
- value
- String
要测试的字符串。The string to test.
返回
如果 true 参数为 value 或 null,或者如果 Empty 仅由空白字符组成,则为 value。true if the value parameter is null or Empty, or if value consists exclusively of white-space characters.
示例
下面的示例创建一个字符串数组,然后将数组的每个元素传递给 IsNullOrWhiteSpace 方法。The following example creates a string array, and then passes each element of the array to the IsNullOrWhiteSpace method.
using System;
public class Example
{
public static void Main()
{
string[] values = { null, String.Empty, "ABCDE",
new String(' ', 20), " \t ",
new String('\u2000', 10) };
foreach (string value in values)
Console.WriteLine(String.IsNullOrWhiteSpace(value));
}
}
// The example displays the following output:
// True
// True
// False
// True
// True
// True
Module Example
Public Sub Main()
Dim values() As String = { Nothing, String.Empty, "ABCDE",
New String(" "c, 20), " " + vbTab + " ",
New String(ChrW(&h2000), 10) }
For Each value As String In values
Console.WriteLine(String.IsNullOrWhiteSpace(value))
Next
End Sub
End Module
' The example displays the following output:
' True
' True
' False
' True
' True
' True
注解
IsNullOrWhiteSpace 是一种简便的方法,类似于以下代码,但它提供了优异的性能:IsNullOrWhiteSpace is a convenience method that is similar to the following code, except that it offers superior performance:
return String.IsNullOrEmpty(value) || value.Trim().Length == 0;
Return String.IsNullOrEmpty(value) OrElse value.Trim().Length = 0
空白字符由 Unicode 标准定义。White-space characters are defined by the Unicode standard. IsNullOrWhiteSpace当将值 true 作为空白字符传递给方法时,该方法将解释返回值的任何字符 Char.IsWhiteSpace 。The IsNullOrWhiteSpace method interprets any character that returns a value of true when it is passed to the Char.IsWhiteSpace method as a white-space character.