Calling XAML Item From ASync Method

Question

I'm just messing around with my first wpf app, and one of the things I've implemented is an insertion sort. I have the sort Method running ASync to the rest of the app, as to not freeze up the rest of the app. I am trying to implement a progress bar to show how far through the sort the computer is, but with no luck.

It gives the exception shown:

So I'm guessing that it doesn't like calling an item in another core, am I right? How do I fix this, and make the progress bar work?

Below is the code

Thanks!

InsertionSort Method:

private int[] performInsertionSort(int[] inputarray)
    {
        for (int i = 0; i < inputarray.Length - 1; i++)
        {
            int j = i + 1;

            while (j > 0)
            {
                if (inputarray[j - 1] > inputarray[j])
                {
                    int temp = inputarray[j - 1];
                    inputarray[j - 1] = inputarray[j];
                    inputarray[j] = temp;

                }
                j--;
                int RealJ = inputarray.Length - j;
                ProgB.Value = inputarray.Length / RealJ * 100;
            }
        }
        return inputarray;
    }

The event handler of the button that starts the InsertionSort Method:

private void button_Click(object sender, RoutedEventArgs e)
    {
        int SInt;
        if (Int32.TryParse(textBox0.Text, out SInt))
            Console.WriteLine(SInt);
        else
            Console.WriteLine("S String could not be parsed.");

        int[] SortList = new int[SInt];
        Random randNum = new Random();
        foreach (int value in SortList)
        {
            randNum.Next(0, 999999);
        }
        new Task(() => { performInsertionSort(SortList); }).Start();
        //performInsertionSort(SortList);
    }