what do checked{} and lock{} blocks mean?

I guess lock is for threading, but what do those two mean?
what other blocks of code are there in C# besides the unsafe{} block? :sick:

checked is used for arithmetic overflows
http://www.codeproject.com/csharp/overflow_checking.asp

there is a locked property which stops controls from being moved a design time, I don't know about a locked{} as a block.

Quote:

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Originally Posted by MrPolite

I guess lock is for threading, but what do those two mean?
what other blocks of code are there in C# besides the unsafe{} block? :sick:

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lock {} creates a mutually exclusive lock on the code block within the brackets, whilst execution is within that block. Can be used to make a procedure/code block thread safe :)

Example from MSDN:

Code:

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// statements_lock2.cs
using System;
using System.Threading;

class Account
{
  int balance;

  Random r = new Random();

  public Account(int initial)
  {
      balance = initial;
  }

  int Withdraw(int amount)
  {

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

      // Comment out the next line to see the effect of leaving out
      // the lock keyword:
      lock (this)
      {
        if (balance >= 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
        {
            return 0; // transaction rejected
        }
      }
  }

  public void DoTransactions()
  {
      for (int i = 0; i < 100; i++)
      {
        Withdraw(r.Next(1, 100));
      }
  }
}

class Test
{
  public static void Main()
  {
      Thread[] threads = new Thread[10];
      Account acc = new Account (1000);
      for (int i = 0; i < 10; i++)
      {
        Thread t = new Thread(new ThreadStart(acc.DoTransactions));
        threads[i] = t;
      }
      for (int i = 0; i < 10; i++)
      {
        threads[i].Start();
      }
  }
}

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the lock{} blocks sounds cool, I dont really have much use for the check and unchecked block though

thanks for the replies :wave: