Using Progress<T> and IProgress<T>

Simple Progress reporting

IProgress<T> can be used to report progress of some procedure to another procedure. This example shows how you can create a basic method that reports its progress.

void Main()
{
    IProgress<int> p = new Progress<int>(progress =>
    {
        Console.WriteLine("Running Step: {0}", progress);
    });
    LongJob(p);
}

public void LongJob(IProgress<int> progress)
{
    var max = 10;
    for (int i = 0; i < max; i++)
    {
        progress.Report(i);
    }
}

Output:

Running Step: 0
Running Step: 3
Running Step: 4
Running Step: 5
Running Step: 6
Running Step: 7
Running Step: 8
Running Step: 9
Running Step: 2
Running Step: 1

Note that when you this code runs, you may see numbers be output out of order. This is because the IProgress<T>.Report() method is run asynchronously, and is therefore not as suitable for situations where the progress must be reported in order.

Using IProgress

It’s important to note that the System.Progress<T> class does not have the Report() method available on it. This method was implemented explicitly from the IProgress<T> interface, and therefore must be called on a Progress<T> when it’s cast to an IProgress<T>.

var p1 = new Progress<int>();
p1.Report(1); //compiler error, Progress does not contain method 'Report'

IProgress<int> p2 = new Progress<int>();
p2.Report(2); //works

var p3 = new Progress<int>();
((IProgress<int>)p3).Report(3); //works