How to add to a List while using Multi-Threading?

Question

I'm kinda new to Multi-Threading and have only played around with it in the past. But I'm curious if it is possible to have a List of byte arrays on a main thread and still be able to add to that List while creating the new byte array in a seperate Thread. Also, I'll be using a for-each loop that will go through a list of forms that will be used to parse into the byte array. So basically a pseudo code would be like this...

reports = new List();

foreach (form in forms)  
{  
    newReport = new Thread(ParseForm(form));  
    reports.Add(newReport);  

}  

void ParseForm(form)  
{  
    newArray = new byte[];  
    newArray = Convert.ToBytes(form);  
    return newArray;  
}

Hopefully the pseudo-code above makes some sense. If anyone could tell me if this is possible and point me in the direction of a good example, I'm sure I can figure out the actual code.

Answer 1

If you need to access a collection from multiple threads, you should either use synchronization, or use a SynchronizedCollection if your .NET version is 3.0 or higher.

Here is one way to make the collection accessible to your thread:

SynchronizedCollection reports = new SynchronizedCollection();

foreach (form in forms) {  
    var reportThread = new Thread(() => ParseForm(form, reports));
    reportThread.Start();
}

void ParseForm(Form form, SynchronizedCollection reports) {  
    newArray = new byte[];  
    newArray = Convert.ToBytes(form);  
    reports.Add(newArray);
}

If you are on .NET 4 or later, a much better alternative to managing your threads manually is presented by various classes of the System.Threading.Tasks namespace. Consider exploring this alternative before deciding on your threading implementation.