How to lock one method by another of same instance in c#

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C#

VB

ASP.NET

I have a two methods say Method1 and Method2 in a class named ClassB and one more class called ClassA.

From classA Starts:
1.creates one instance of ClassB and classB constuctor invoke the timer(which used to call MethodB for every 10 mins )
2.creates thread to call MethodA for every 10 seconds.

while MethodB is updating (by the invocation of timer),i need to lock MethodA of ClassB.

Since MethodA and MethodB are using same static variables.I want to update settings from MethodB at that time i need to stop processing on MethodA.

Here is my code:

using System;
using System.Threading;

namespace ConsoleApplication1
{
    // ThreadLock.cs
    class ThreadLock
    {
        public static void DoLock()
        {
            Thread[] threads = new Thread[10];
            Account acc = new Account(1000);
            for (int i = 0; i < 10; i++)
            {
                Thread t = new Thread(new ParameterizedThreadStart(acc.DoTransactions));
                threads[i] = t;
            }
            for (int i = 0; i < 10; i++)
            {
                threads[i].Start(i+1);
                Thread.Sleep(1000);
            }
        }
    }

    class Account
    {
        private Object thisLock = new Object();
        private System.Threading.Timer updateBalanceThread = null;
        int balance;

        Random r = new Random();

        public Account(int initial)
        {
            balance = initial;

            //Update balance every 10 sec
            updateBalanceThread = new System.Threading.Timer(new TimerCallback(UpdateBalance), null, TimeSpan.FromSeconds(10), TimeSpan.FromSeconds(10));

        }

        /// <summary>
        /// Update Balance
        /// Issue:During balance update,i need to wait withdrawal process after update only allow to withdraw
        /// </summary>
        /// &lt;param name="Balance"&gt;&lt;/param&gt;
        public void UpdateBalance(object Balance)
        {
            //when i update balance i need to stop withdrawal
            balance += 1000;
            Thread.Sleep(1000);
        }

        int Withdraw(int amount)
        {

            // This condition will never be true unless the lock statement
            // is commented out:
            if (balance &lt; 0)
            {
                throw new Exception("Negative Balance");
            }

            // Comment out the next line to see the effect of leaving out 
            // the lock keyword:
            lock (thisLock)
            {
              
                if (balance &gt;= amount)
                {
                    Console.WriteLine("Balance before Withdrawal :  " + balance);
                    Console.WriteLine("Amount to Withdraw        : -" + amount);
                    balance = balance - amount;
                    Console.WriteLine("Balance after Withdrawal  :  " + balance);
                    return amount;
                }
                else
                {
                    Console.WriteLine("Balance:" + balance + "---Withdrawal  :  " + amount);
                    return 0; // transaction rejected
                }
            }
        }

        public void DoTransactions(object threadNo)
        {
            //Need lock here

            Console.WriteLine("Threand Number:" + (string)threadNo.ToString());

            for (int i = 0; i &lt; 10; i++)
            {
                Withdraw(r.Next(1, 10));
            }          
        }
    }
}

Anyone solve my problem?