String.IsNullOrEmpty(String) Methode

  • Referenz

Definition

Namespace:
System
Assembly:
System.Runtime.dll
Assembly:
mscorlib.dll
Assembly:
netstandard.dll
Quelle:
String.cs
Quelle:
String.cs
Quelle:
String.cs

Gibt an, ob die angegebene Zeichenfolge null oder eine leere Zeichenfolge ("") ist.

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

Parameter

value
String

Die zu testende Zeichenfolge.

Gibt zurück

Boolean

true, wenn der value-Parameter null oder eine leere Zeichenfolge ("") ist; andernfalls false.

Beispiele

Im folgenden Beispiel werden drei Zeichenfolgen untersucht und bestimmt, ob jede Zeichenfolge einen Wert hat, eine leere Zeichenfolge ist oder nullist.

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.

let test (s: string): string =
    if String.IsNullOrEmpty(s)
    then "is null or empty"
    else $"(\"{s}\") is neither null nor empty"

let s1 = "abcd"
let s2 = ""
let s3 = null

printfn "String s1 %s" (test s1)
printfn "String s2 %s" (test s2)
printfn "String s2 %s" (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.

Hinweise

Weitere Informationen zu dieser API finden Sie unter Zusätzliche API-Hinweise für String.IsNullOrEmpty.

Gilt für:

Weitere Informationen