Csharp/CSharp Tutorial/Thread/ReaderWriterLock

Reader Lock

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Reflection;
using System.Runtime;
using System.Runtime.rupilerServices;
using System.Security;
using System.Text;
using System.Threading;
public class MainClass
{
    
    public static void Main()
    {
       ReaderWriterLock rwLock = new ReaderWriterLock();
        rwLock.AcquireReaderLock(250);
        if (!rwLock.IsReaderLockHeld)
           return;
        Console.WriteLine("Reader lock held");
        
        LockCookie cookie = rwLock.UpgradeToWriterLock(250);
        if (rwLock.IsWriterLockHeld)
        {
            Console.WriteLine("Upgraded to writer lock");
            rwLock.DowngradeFromWriterLock(ref cookie);
        }
        rwLock.ReleaseReaderLock();
    }
}

Reader lock held
Upgraded to writer lock

Using a reader-writer lock to protect a complex business type

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Reflection;
using System.Runtime;
using System.Runtime.rupilerServices;
using System.Security;
using System.Text;
using System.Threading;
class Account
{
    public string company ="No Name";
    public decimal balance= 0.0m;
    public DateTime lastUpdate = DateTime.Now;
    public ReaderWriterLock syncLock = new ReaderWriterLock();
    public decimal AutoUpdateBalance(decimal delta)
    {
        syncLock.AcquireWriterLock(-1);
        try
        {
            balance += delta;
            lastUpdate = DateTime.Now;
            return balance;
        }
        finally
        {
            syncLock.ReleaseWriterLock();
        }
    }
    public void GetState(out string company, out decimal balance, out DateTime lastUpdate)
    {
        syncLock.AcquireReaderLock(-1);
        try
        {
            company = this.rupany;
            balance = this.balance;
            lastUpdate = this.lastUpdate;
        }
        finally
        {
            syncLock.ReleaseReaderLock();
        }
    }
}

public class MainClass
{
    
    public static void Main()
    {
        Account account = new Account();
        string company;
        decimal balance;
        DateTime lastUpdate;
        account.GetState(out company, out balance, out lastUpdate);
        Console.WriteLine("{0}, balance: {1}, last updated: {2}",company, balance, lastUpdate);
    }
}

No Name, balance: 0.0, last updated: 25/03/2007 3:04:25 PM

Writer Lock

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Reflection;
using System.Runtime;
using System.Runtime.rupilerServices;
using System.Security;
using System.Text;
using System.Threading;
public class MainClass
{
    
    public static void Main()
    {
       ReaderWriterLock rwLock = new ReaderWriterLock();
        rwLock.AcquireWriterLock(250);
        if (rwLock.IsWriterLockHeld)
        {
            Console.WriteLine("Writer lock held");
            rwLock.ReleaseWriterLock();
        }
        rwLock.ReleaseWriterLock();
    }
}

Writer lock held
Unhandled Exception: System.ApplicationException: Attempt to release mutex not owned by caller. (Exc
eption from HRESULT: 0x00000120)
   at System.Threading.ReaderWriterLock.ReleaseWriterLockInternal()
   at MainClass.Main()