# String.IsNullOrEmpty(String) Metoda

## Definicja

Wskazuje, czy określony ciąg jest `null` lub pustym ciągiem ("").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``

#### Parametry

value
String

Ciąg do przetestowania.The string to test.

#### Zwraca

Boolean

`true` Jeśli `value` parametr jest `null` lub jest ciągiem pustym (""); w przeciwnym razie `false` .`true` if the `value` parameter is `null` or an empty string (""); otherwise, `false`.

Poniższy przykład analizuje trzy ciągi i określa, czy każdy ciąg ma wartość, jest pustym ciągiem lub jest `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.
``````

## Uwagi

IsNullOrEmpty jest wygodną metodą, która umożliwia jednoczesne testowanie, czy String jest `null` lub jej wartość String.Empty .IsNullOrEmpty is a convenience method that enables you to simultaneously test whether a String is `null` or its value is String.Empty. Odpowiada to następującemu kodowi: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
``````

Możesz użyć IsNullOrWhiteSpace metody, aby sprawdzić, czy ciąg jest `null` , jego wartość String.Empty lub zawiera tylko znaki odstępu.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.

### Co to jest ciąg o wartości null?What is a null string?

Ciąg jest, `null` Jeśli nie ma przypisanej wartości (w języku C++ i Visual Basic) lub jeśli został jawnie przypisany do wartości `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`. Mimo że funkcja formatowania złożonego może bezpiecznie obsłużyć ciąg o wartości null, jak pokazano w poniższym przykładzie, próba wywołania jednego z nich powoduje, że jego członkowie zgłaszają NullReferenceException .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.
``````

### Co to jest pusty ciąg?What is an empty string?

Ciąg jest pusty, jeśli jest jawnie przypisany do pustego ciągu ("") lub String.Empty .A string is empty if it is explicitly assigned an empty string ("") or String.Empty. Pusty ciąg ma Length wartość 0.An empty string has a Length of 0. Poniższy przykład tworzy pusty ciąg i wyświetla jego wartość oraz jego długość.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.
``````