String::IsNullOrEmpty Method (String^)
Indicates whether the specified string is null or an Empty string.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- value
-
Type:
System::String^
The string to test.
Return Value
Type: System::Booleantrue if the value parameter is null or an empty string (""); otherwise, false.
IsNullOrEmpty is a convenience method that enables you to simultaneously test whether a String is null or its value is Empty. It is equivalent to the following code:
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.
A string is null if it has not been assigned a value (in C++ and Visual Basic) or if has explicitly been assigned a value of null. 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.
A string is empty if it is explicitly assigned an empty string ("") or String::Empty. An empty string has a Length of 0. The following example creates an empty string and displays its value and its length.
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.
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1