According to Microsoft: 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.
The lock keyword calls Enter at the start of the block and Exit at the end of the block. lock keyword actually handles Monitor class at the back end.
It is so easy to do it. Here is an example:
private static readonly Object obj = new Object();
lock (obj)
{
// critical section
}
In the above code, first, the thread enters a critical section, and then it will lock obj. When another thread tries to enter, it will also try to lock obj, which is already locked by the first thread. The second thread will have to wait for the first thread to release obj. When the first thread leaves, then another thread will lock obj and will enter the critical section.