The lock keyword marks a statement block as a critical section by obtaining the mutual-exclusion lock for a given object, executing a statement, and then releasing the lock. The following example includes a lock statement.
The lock keyword ensures that one thread does not enter a critical section of code while another thread is in the critical section. If another thread tries to enter a locked code, it will wait, block, until the object is released.
As long as the lock statement is present, the statement block is a critical section and balance will never become a negative number. See the following example.
//Account.cs
class Account
{
decimal balance;
private Object thisLock = new Object();
public void Withdraw(decimal amount)
{
lock (thisLock)
{
if (amount > balance)
{
throw new Exception("Insufficient funds");
}
balance -= amount;
}
}
}
}
