如何在C＃中使用多线程？

Question

In my project, i have to do something much much times in a foreach loop which i need to wait it about 6-7 hours.

for example: i have 80 docs to check => about 8 hours

foreach (var doc in docs)
{
    bool valid = checkIsValid(doc); // about 2 min per doc
    if (vaid)
    {
        doThing(doc); // about 5 min per doc
    }
    else
    {
        delete(doc); // about 20s per doc
    }
}

So, i consider can i check these things in the same time which i have lots of resources is not using when running the above code. And i find C# has a multithread feature (i don't know what can it provides).

Can i use it in my project? How to use it in my project?

ideal: 80 docs are checking in the same time and the foreach loop will finish when 80 threads have died.

foreach (var doc in docs)
{
    //new thread start
    bool valid = checkIsValid(doc); // about 2 min per doc
    if (vaid)
    {
        doThing(doc); // about 5 min per doc
    }
    else
    {
        delete(doc); // about 20s per doc
    }
    //thread die
}

Answer 1

Have you looked at Parallel.ForEach ? Your code would look like:

Parallel.ForEach(docs, doc => {
    if (checkIsValid(doc))
        doThing(doc);
    else
        delete(doc);
});

Answer 2

There are multiple ways to achieve concurrency in C# but the time taken by each method depends on the number of cores you have. 'Parallel.ForEach' is one option and probably the simplest way to achieve, but note that it will try to break your work item where possible and will speed up the execution.

The following code is to have multi threading but be careful 80 threads might be an overkill. So create tasks (threads) with proper consideration

foreach (var doc in docs)
{
    //new thread start
    bool valid = checkIsValid(doc); // about 2 min per doc
    if (vaid)
    {
        Task.Factory.StartNew(() => doThing(doc);
    }
    else
    {
        delete(doc); // about 20s per doc
    }
    //thread die
}

Tasks work in framework 4 and above