object ICollection.SyncRoot 
{ 
     get 
     { 
          if (this._syncRoot == null) 
          { 
               ICollection items = this.items as ICollection; 
               if (items != null) 
               { 
                    this._syncRoot = items.SyncRoot; 
               } 
               else 
               { 
                    Interlocked.CompareExchange(ref this._syncRoot, new object(), null); 
               } 
          } 
          return this._syncRoot; 
     } 
} 

object ICollection.SyncRoot 
{ 
     get 
     { 
          if (this._syncRoot == null) 
          { 
               Interlocked.CompareExchange(ref this._syncRoot, new object(), null); 
          } 
          return this._syncRoot; 
     } 
} 
  

public object SyncRoot 
{ 
     get 
     { 
          return this; 
     } 
} 

lock(x) 
{ 
  DoSomething(); 
} 

System.Object obj = (System.Object)x; 
System.Threading.Monitor.Enter(obj); 
try 
{ 
  DoSomething(); 
} 
finally 
{ 
  System.Threading.Monitor.Exit(obj); 
}