volatile (C# Reference)
The volatile keyword indicates that a field might be modified by multiple threads that are executing at the same time. Fields that are declared volatile are not subject to compiler optimizations that assume access by a single thread. This ensures that the most up-to-date value is present in the field at all times.
The volatile modifier is usually used for a field that is accessed by multiple threads without using the lock statement to serialize access. See How to: Create and Terminate Threads (C# Programming Guide) for an example of volatile in a multi-threaded scenario.
The volatile keyword can be applied to fields of these types:
Reference types.
Pointer types (in an unsafe context). Note that although the pointer itself can be volatile, the object that it points to cannot. In other words, you cannot declare a "pointer to volatile."
Types such as sbyte, byte, short, ushort, int, uint, char, float, and bool.
An enum type with one of the following base types: byte, sbyte, short, ushort, int, or uint.
Generic type parameters known to be reference types.
The volatile keyword can only be applied to fields of a class or struct. Local variables cannot be declared volatile.
Example
The following example shows how to declare a public field variable as volatile.
class VolatileTest
{
public volatile int i;
public void Test(int _i)
{
i = _i;
}
}
C# Language Specification
For more information, see the following sections in the C# Language Specification:
3.10 Execution order
10.5.3 Volatile fields
See Also
Concepts
Reference
Other Resources
Change History
Date |
History |
Reason |
|---|---|---|
January 2010 |
Revised the list of types to which volatile can be applied. |
Customer feedback. |