String.IsNullOrEmpty(String) 메서드

정의

지정된 문자열이 null이거나 빈 문자열("")인지를 나타냅니다.Indicates whether the specified string is null or an empty string ("").

public:
 static bool IsNullOrEmpty(System::String ^ value);
public static bool IsNullOrEmpty (string value);
static member IsNullOrEmpty : string -> bool
Public Shared Function IsNullOrEmpty (value As String) As Boolean

매개 변수

value
String

테스트할 문자열입니다.The string to test.

반환

Boolean

true 매개 변수가 value이거나 빈 문자열("")이면 null이고, 그러지 않으면 false입니다.true if the value parameter is null or an empty string (""); otherwise, false.

예제

다음 예에서는 세 개의 문자열을 검사 하 고 각 문자열이 값을 포함 하는지, 빈 문자열 인지 또는 인지를 확인 합니다 null .The following example examines three strings and determines whether each string has a value, is an empty string, or is null.

using namespace System;
String^ Test( String^ s )
{
   if (String::IsNullOrEmpty(s))
      return "is null or empty";
   else
      return String::Format( "(\"{0}\") is neither null nor empty", s );
}

int main()
{
   String^ s1 = "abcd";
   String^ s2 = "";
   String^ s3 = nullptr;
   Console::WriteLine( "String s1 {0}.", Test( s1 ) );
   Console::WriteLine( "String s2 {0}.", Test( s2 ) );
   Console::WriteLine( "String s3 {0}.", Test( s3 ) );
}
// The example displays the following output:
//       String s1 ("abcd") is neither null nor empty.
//       String s2 is null or empty.
//       String s3 is null or empty.
string s1 = "abcd";
string s2 = "";
string s3 = null;

Console.WriteLine("String s1 {0}.", Test(s1));
Console.WriteLine("String s2 {0}.", Test(s2));
Console.WriteLine("String s3 {0}.", Test(s3));

String Test(string s)
{
if (String.IsNullOrEmpty(s))
    return "is null or empty";
else
    return String.Format("(\"{0}\") is neither null nor empty", s);
}

// The example displays the following output:
//       String s1 ("abcd") is neither null nor empty.
//       String s2 is null or empty.
//       String s3 is null or empty.
Class Sample
   Public Shared Sub Main()
      Dim s1 As String = "abcd"
      Dim s2 As String = ""
      Dim s3 As String = Nothing
      
      Console.WriteLine("String s1 {0}.", Test(s1))
      Console.WriteLine("String s2 {0}.", Test(s2))
      Console.WriteLine("String s3 {0}.", Test(s3))
   End Sub
   
   Public Shared Function Test(s As String) As String
      If String.IsNullOrEmpty(s) Then
         Return "is null or empty"
      Else
         Return String.Format("(""{0}"") is neither null nor empty", s)
      End If
   End Function 
End Class  
' The example displays the following output:
'       String s1 ("abcd") is neither null nor empty.
'       String s2 is null or empty.
'       String s3 is null or empty.

설명

IsNullOrEmptyString 가 인지 null 또는 해당 값 인지를 동시에 테스트할 수 있게 해 주는 편리한 메서드입니다 String.Empty .IsNullOrEmpty is a convenience method that enables you to simultaneously test whether a String is null or its value is String.Empty. 다음 코드와 동일 합니다.It is equivalent to the following code:

result = s == nullptr || s == String::Empty;
bool TestForNullOrEmpty(string s)
{
    bool result;
    result = s == null || s == string.Empty;
    return result;
}

string s1 = null;
string s2 = "";
Console.WriteLine(TestForNullOrEmpty(s1));
Console.WriteLine(TestForNullOrEmpty(s2));

// The example displays the following output:
//    True
//    True
result = s Is Nothing OrElse s = String.Empty

메서드를 사용 하 여 IsNullOrWhiteSpace 문자열이 인지 null , 해당 값이 String.Empty 이거나 공백 문자로만 구성 되어 있는지를 테스트할 수 있습니다.You can use the IsNullOrWhiteSpace method to test whether a string is null, its value is String.Empty, or it consists only of white-space characters.

Null 문자열 이란?What is a null string?

문자열은 null 값이 할당 되지 않은 경우 (c + + 및 Visual Basic) 이거나 명시적으로 값이 할당 된 경우에는입니다 null .A string is null if it has not been assigned a value (in C++ and Visual Basic) or if it has explicitly been assigned a value of null. 다음 예제와 같이 복합 서식 지정 기능에서 null 문자열을 정상적으로 처리할 수 있지만, 해당 멤버가를 throw 하는 경우이를 호출 하려고 시도 하는 것 NullReferenceException 입니다.Although the composite formatting feature can gracefully handle a null string, as the following example shows, attempting to call one if its members throws a NullReferenceException.

using namespace System;

void main()
{
   String^ s;
  
   Console::WriteLine("The value of the string is '{0}'", s);

   try {
      Console::WriteLine("String length is {0}", s->Length);
   }
   catch (NullReferenceException^ e) {
      Console::WriteLine(e->Message);
   }   
}
// The example displays the following output:
//     The value of the string is ''
//     Object reference not set to an instance of an object.
  String s = null;

  Console.WriteLine("The value of the string is '{0}'", s);

  try 
  {
      Console.WriteLine("String length is {0}", s.Length);
  }
  catch (NullReferenceException e) 
  {
      Console.WriteLine(e.Message);
  }

  // The example displays the following output:
  //     The value of the string is ''
  //     Object reference not set to an instance of an object.
Module Example
   Public Sub Main()
      Dim s As String

      Console.WriteLine("The value of the string is '{0}'", s)

      Try 
         Console.WriteLine("String length is {0}", s.Length)
      Catch e As NullReferenceException
         Console.WriteLine(e.Message)
      End Try   
   End Sub
End Module
' The example displays the following output:
'     The value of the string is ''
'     Object reference not set to an instance of an object.

빈 문자열은 무엇 인가요?What is an empty string?

빈 문자열 ("") 또는에 명시적으로 할당 된 문자열은 비어 있습니다 String.Empty .A string is empty if it is explicitly assigned an empty string ("") or String.Empty. 빈 문자열에는 Length 0이 있습니다.An empty string has a Length of 0. 다음 예에서는 빈 문자열을 만들고 해당 값과 해당 길이를 표시 합니다.The following example creates an empty string and displays its value and its length.

String^ s = "";
Console::WriteLine("The length of '{0}' is {1}.", s, s->Length);
// The example displays the following output:
//       The length of '' is 0.      
String s = "";
Console.WriteLine("The length of '{0}' is {1}.", s, s.Length);

// The example displays the following output:
//       The length of '' is 0.      
Dim s As String = ""
Console.WriteLine("The length of '{0}' is {1}.", s, s.Length)
' The example displays the following output:
'        The length of '' is 0.      

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