String.IsNullOrEmpty(String) Method
Definition
Important
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Indicates whether the specified string is null
or an empty string ("").
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
Parameters
- value
- String
The string to test.
Returns
true
if the value
parameter is null
or an empty string (""); otherwise, false
.
Examples
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.
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.
Remarks
For more information about this API, see Supplemental API remarks for String.IsNullOrEmpty.
Applies to
See also
Tee yhteistyötä kanssamme GitHubissa
Tämän sisällön lähde on GitHubissa, jossa voit myös luoda ja tarkastella ongelmia ja pull-pyyntöjä. Katso lisätietoja osallistujan oppaasta.