Error while debugging - Unable to evaluate the expression. Operation not supported. Unknown error: 0x80070057

I'm currently learning c#, using a head first book. it gave us some code to write and telling me to debug and use watch. in the book the value says 15 and type int, but for me i'm getting

number Unable to evaluate the expression. Operation not supported. Unknown error: 0x80070057.

I've written the code EXACTLY the same way as is in the code so i don't get it? here's a screenshot:

and here's the code:

 private void Button_Click(object sender, RoutedEventArgs e)
    {
        int number = 15;
        number = number + 10;
        number = 36 * 15;
        number = 12 - (42 / 7);
        number += 10;
        number *= 3;
        number = 71 / 3;

        int count = 0;
        count ++;
        count --;

        string result = "hello";
        result += " again " + result;
        output.Text = result;
        result = "the value is: " + count;
        result = "";

        bool yesNo = false;
        bool anotherBool = true;
        yesNo = !anotherBool;
    }

using Visual Studio 2019.