Volatile Class
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Contains methods for performing volatile memory operations.
Assembly: mscorlib (in mscorlib.dll)
| Name | Description | |
|---|---|---|
  | Read(Boolean%) | Reads the value of the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears after this method in the code, the processor cannot move it before this method. |
| Read(Byte%) | Reads the value of the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears after this method in the code, the processor cannot move it before this method. |
| Read(Double%) | Reads the value of the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears after this method in the code, the processor cannot move it before this method. |
| Read(Int16%) | Reads the value of the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears after this method in the code, the processor cannot move it before this method. |
| Read(Int32%) | Reads the value of the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears after this method in the code, the processor cannot move it before this method. |
| Read(Int64%) | Reads the value of the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears after this method in the code, the processor cannot move it before this method. |
| Read(IntPtr%) | Reads the value of the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears after this method in the code, the processor cannot move it before this method. |
| Read(SByte%) | Reads the value of the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears after this method in the code, the processor cannot move it before this method. |
| Read(Single%) | Reads the value of the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears after this method in the code, the processor cannot move it before this method. |
| Read(UInt16%) | Reads the value of the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears after this method in the code, the processor cannot move it before this method. |
| Read(UInt32%) | Reads the value of the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears after this method in the code, the processor cannot move it before this method. |
| Read(UInt64%) | Reads the value of the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears after this method in the code, the processor cannot move it before this method. |
| Read(UIntPtr%) | Reads the value of the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears after this method in the code, the processor cannot move it before this method. |
| Read<T>(T%) | Reads the object reference from the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears after this method in the code, the processor cannot move it before this method. |
| Write(Boolean%, Boolean) | Writes the specified value to the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears before this method in the code, the processor cannot move it after this method. |
| Write(Byte%, Byte) | Writes the specified value to the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears before this method in the code, the processor cannot move it after this method. |
| Write(Double%, Double) | Writes the specified value to the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears before this method in the code, the processor cannot move it after this method. |
| Write(Int16%, Int16) | Writes the specified value to the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears before this method in the code, the processor cannot move it after this method. |
| Write(Int32%, Int32) | Writes the specified value to the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears before this method in the code, the processor cannot move it after this method. |
| Write(Int64%, Int64) | Writes the specified value to the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a memory operation appears before this method in the code, the processor cannot move it after this method. |
| Write(IntPtr%, IntPtr) | Writes the specified value to the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears before this method in the code, the processor cannot move it after this method. |
| Write(SByte%, SByte) | Writes the specified value to the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears before this method in the code, the processor cannot move it after this method. |
| Write(Single%, Single) | Writes the specified value to the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears before this method in the code, the processor cannot move it after this method. |
| Write(UInt16%, UInt16) | Writes the specified value to the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears before this method in the code, the processor cannot move it after this method. |
| Write(UInt32%, UInt32) | Writes the specified value to the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears before this method in the code, the processor cannot move it after this method. |
| Write(UInt64%, UInt64) | Writes the specified value to the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears before this method in the code, the processor cannot move it after this method. |
| Write(UIntPtr%, UIntPtr) | Writes the specified value to the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears before this method in the code, the processor cannot move it after this method. |
| Write<T>(T%, T) | Writes the specified object reference to the specified field. On systems that require it, inserts a memory barrier that prevents the processor from reordering memory operations as follows: If a read or write appears before this method in the code, the processor cannot move it after this method. |
On a multiprocessor system, a volatile write operation ensures that a value written to a memory location is immediately visible to all processors. A volatile read operation obtains the very latest value written to a memory location by any processor. These operations might require flushing processor caches, which can affect performance.
 Note: |
|---|
On a uniprocessor system, volatile reads and writes ensure that a value is read or written to memory and not cached (for example, in a processor register). Thus, you can use these operations to synchronize access to a field that can be updated by another thread or by hardware. |
Volatile memory operations are for special cases of synchronization, where normal locking is not an acceptable alternative. Under normal circumstances, the C# lock statement, the Visual Basic SyncLock statement, and the Monitor class provide the easiest and least error-prone way of synchronizing access to data, and the Lazy<T> class provides a simple way to write lazy initialization code without directly using double-checked locking.
The Volatile::Read and Volatile::Write methods enable functionality that is not supported in languages. For example:
Some languages, such as Visual Basic, do not recognize the concept of volatile memory operations. The Volatile class provides that functionality in such languages.
Note:Calling one of these methods affects only a single memory access. To provide effective synchronization for a field, all access to the field must use Volatile::Read and Volatile::Write.
In C#, using the volatile modifier on a field guarantees that every access to that field uses the Volatile::Read and Volatile::Write methods, but the volatile modifier cannot be applied to array elements. The Volatile::Read and Volatile::Write methods can be used on array elements.
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