﻿<?xml version="1.0" encoding="utf-8"?><Type Name="DoubleCheckLockingRule" FullName="Gendarme.Rules.Concurrency.DoubleCheckLockingRule"><TypeSignature Language="C#" Value="public class DoubleCheckLockingRule : Gendarme.Framework.Rule, Gendarme.Framework.IMethodRule" /><TypeSignature Language="ILAsm" Value=".class public auto ansi beforefieldinit DoubleCheckLockingRule extends Gendarme.Framework.Rule implements class Gendarme.Framework.IMethodRule, class Gendarme.Framework.IRule" /><AssemblyInfo><AssemblyName>Gendarme.Rules.Concurrency</AssemblyName><AssemblyVersion>4.2.0.0</AssemblyVersion></AssemblyInfo><Base><BaseTypeName>Gendarme.Framework.Rule</BaseTypeName></Base><Interfaces><Interface><InterfaceName>Gendarme.Framework.IMethodRule</InterfaceName></Interface></Interfaces><Attributes><Attribute><AttributeName>Gendarme.Framework.EngineDependency(typeof(Gendarme.Framework.Engines.OpCodeEngine))</AttributeName></Attribute><Attribute><AttributeName>Gendarme.Framework.Problem("This method uses the potentially unreliable double-check locking technique.")</AttributeName></Attribute><Attribute><AttributeName>Gendarme.Framework.Solution("Remove the check that occurs outside of the protected region.")</AttributeName></Attribute></Attributes><Docs><summary>
             This rule is used to check for the double-check pattern, often used when implementing 
             the singleton pattern (1), and warns of potential incorrect usage. 
             
             The original CLR (1.x) could not guarantee that a double-check would work correctly 
             in multithreaded applications. However the technique does work on the x86 architecture, 
             the most common architecture, so the problem is seldom seen (e.g. IA64).
             
             The CLR 2 and later introduce a strong memory model (2) where a double check for a
             <c>lock</c> is correct (as long as you assign to a <c>volatile</c> variable). This
             rule won't report a defect for assemblies targetting the 2.0 (and later) runtime.
             <list><item><term>1. Implementing Singleton in C#</term><description>
             http://msdn.microsoft.com/en-us/library/ms998558.aspx</description></item><item><term>2. Understand the Impact of Low-Lock Techniques in Multithreaded Apps</term><description>http://msdn.microsoft.com/en-ca/magazine/cc163715.aspx#S5</description></item></list></summary><remarks>To be added.</remarks><example>
             Bad example:
             <code>
             public class Singleton {
            	private static Singleton instance;
            	private static object syncRoot = new object ();
             
            	public static Singleton Instance {
             		get {
            			if (instance == null) {
            				lock (syncRoot) {
            					if (instance == null) {
            						instance = new Singleton ();
            					}
            				}
            			}
            			return instance;
            		}
            	}
             }
             </code></example><example>
             Good example (for 1.x code avoid using double check):
             <code>
             public class Singleton {
            	private static Singleton instance;
            	private static object syncRoot = new object ();
             
            	public static Singleton Instance {
             		get {
             			// do not check instance before the lock
             			// this will work on all CLRs but will affect 
             			// performance since the lock is always acquired
            			lock (syncRoot) {
            				if (instance == null) {
            					instance = new Singleton ();
            				}
            			}
            			return instance;
            		}
            	}
             }
             </code></example><example>
             Good example (for 2.x and later):
             <code>
             public class Singleton {
            	// by using 'volatile' the double check will work under CLR 2.x
            	private static volatile Singleton instance;
            	private static object syncRoot = new object ();
             
            	public static Singleton Instance {
             		get {
            			if (instance == null) {
            				lock (syncRoot) {
            					if (instance == null) {
            						instance = new Singleton ();
            					}
            				}
            			}
            			return instance;
            		}
            	}
             }
             </code></example></Docs><Members><Member MemberName=".ctor"><MemberSignature Language="C#" Value="public DoubleCheckLockingRule ();" /><MemberSignature Language="ILAsm" Value=".method public hidebysig specialname rtspecialname instance void .ctor() cil managed" /><MemberType>Constructor</MemberType><AssemblyInfo><AssemblyVersion>4.2.0.0</AssemblyVersion></AssemblyInfo><Parameters /><Docs><summary>To be added.</summary><remarks>To be added.</remarks></Docs></Member><Member MemberName="CheckMethod"><MemberSignature Language="C#" Value="public Gendarme.Framework.RuleResult CheckMethod (Mono.Cecil.MethodDefinition method);" /><MemberSignature Language="ILAsm" Value=".method public hidebysig newslot virtual instance valuetype Gendarme.Framework.RuleResult CheckMethod(class Mono.Cecil.MethodDefinition method) cil managed" /><MemberType>Method</MemberType><AssemblyInfo><AssemblyVersion>4.2.0.0</AssemblyVersion></AssemblyInfo><ReturnValue><ReturnType>Gendarme.Framework.RuleResult</ReturnType></ReturnValue><Parameters><Parameter Name="method" Type="Mono.Cecil.MethodDefinition" /></Parameters><Docs><param name="method">To be added.</param><summary>To be added.</summary><returns>To be added.</returns><remarks>To be added.</remarks></Docs></Member><Member MemberName="Initialize"><MemberSignature Language="C#" Value="public override void Initialize (Gendarme.Framework.IRunner runner);" /><MemberSignature Language="ILAsm" Value=".method public hidebysig virtual instance void Initialize(class Gendarme.Framework.IRunner runner) cil managed" /><MemberType>Method</MemberType><AssemblyInfo><AssemblyVersion>4.2.0.0</AssemblyVersion></AssemblyInfo><ReturnValue><ReturnType>System.Void</ReturnType></ReturnValue><Parameters><Parameter Name="runner" Type="Gendarme.Framework.IRunner" /></Parameters><Docs><param name="runner">To be added.</param><summary>To be added.</summary><remarks>To be added.</remarks></Docs></Member></Members></Type>