asp.net String.IsNullOrEmpty 方法简介_计算机技术学习交流网

此方法在 .NET Framework 2.0 版中是新增的。
指示指定的 String 对象是空引用（在 Visual Basic 中为 Nothing）还是 Empty 字符串。
这个方法在VB，VB.Net, C#,C++,JScript,J#中都有，很好很强大的一个方法。
String.Empty 字段
表示空字符串。此字段为只读。
命名空间:System
程序集:mscorlib（在 mscorlib.dll 中）
语法
Visual Basic（声明）
Public Shared ReadOnly Empty As String
Visual Basic（用法）
Dim value As String
value = String.Empty
C#
public static readonly string Empty
C++
public:
static initonly String^ Empty
J#
public static final String Empty
JScript
public static final var Empty : String
备注
此字段的值为零长度字符串 ""。
示例
下面的代码示例演示如何使用 Empty 字段。
在第一个示例中，如果另一个字段的值为空引用（在 Visual Basic 中为 Nothing），则 Empty 字符串作为默认值返回。
Visual Basic 复制代码

[复制此代码]CODE:

Dim myBinding As DataBinding = DataBindings("Text") 
If Not (myBinding Is Nothing) Then 
Return myBinding.Expression 
End If 
Return [String].Empty 
End Get 

C# 复制代码

[复制此代码]CODE:

DataBinding myBinding = DataBindings["Text"]; 
if (myBinding != null) 
{ 
return myBinding.Expression; 
} 
return String.Empty; 

C++ 复制代码

[复制此代码]CODE:

DataBinding^ myBinding = DataBindings[ "Text" ]; 
if ( myBinding != nullptr ) 
{ 
return myBinding->Expression; 
} 
return String::Empty; 

J# 复制代码

[复制此代码]CODE:

DataBinding myBinding = get_DataBindings().get_Item("Text"); 
if (myBinding != null) { 
return myBinding.get_Expression(); 
} 
return(""); 

在第二个示例中，Compare 中使用了 Empty 字符串来测试子字符串。
Visual Basic 复制代码

[复制此代码]CODE:

Dim myString As String = "abc" 
Dim test1 As Boolean = String.Compare(myString.Substring(2, 1), "c") = 0 ' This is true. 
myString.Substring(3, 1) ' This throws ArgumentOutOfRangeException. 
Dim test2 As Boolean = String.Compare(myString.Substring(3, 0), String.Empty) = 0 ' This is true. 

C# 复制代码

[复制此代码]CODE:

String myString = "abc"; 
bool test1 = String.Compare(myString.Substring(2, 1), "c") == 0; // This is true. 
myString.Substring(3, 1); // This throws ArgumentOutOfRangeException. 
bool test2 = String.Compare(myString.Substring(3, 0), String.Empty) == 0; // This is true. 

C++ 复制代码

[复制此代码]CODE:

String^ myString = "abc"; 
bool test1 = String::Compare( myString->Substring( 2, 1 ), "c" ) == 0; // This is true. 
myString->Substring( 3, 1 ); // This throws ArgumentOutOfRangeException. 
bool test2 = String::Compare( myString->Substring( 3, 0 ), String::Empty ) == 0; // This is true. 

J# 复制代码

[复制此代码]CODE:

String myString = "abc"; 
// This is true. 
boolean test1 = String.Compare(myString.Substring(2, 1), "c") == 0; 
myString.Substring(3, 1); // This throws ArgumentOutOfRangeException. 
// This is true. 
boolean test2 = String.Compare(myString.Substring(3, 0), " ") == 0; 

JScript 复制代码

[复制此代码]CODE:

var myString : String = "abc"; 
var test1 : boolean = String.Compare(myString.Substring(2, 1), "c") == 0; // This is true. 
myString.
	

asp.net String.IsNullOrEmpty 方法简介

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