Using Monitor Class For Thread Synchronization
While developing a multithreaded application it is very important to maintain synchronization between multiple calls to the same method. Consider for example that you have a function that writes to a file. If at the same time multiple threads call this function it is bound to throw an exception as previous method call is yet to finish with the file. To avoid such situations you can use Monitor class.
Following namespaces are involved in our example:
Using Monitor class
Monitor class can synchronize method calls using its Enter and Exit methods. Following code shows how these methods work:
Dim fs As FileStream = New FileStream
Dim t As Thread = Thread.CurrentThread
fs.Write(Encoding.ASCII.GetBytes(t.Name & vbCrLf),
0, t.Name.Length + 2)
Dim i As Integer
For i = 0 To 10000
fs.Write(Encoding.ASCII.GetBytes(i & ","),
0, i.ToString().Length + 1)
Here, we called Monitor.Enter method at the start of the method followed by our code that writes into a file. Once the writing operation is complete we call Monitor.Exit method. This ensures that till the time one thread is executing the function any other thread can not execute the same function. You can easily check what happens if you do not use Monitor class by simply commenting these two lines.