Streamlining writing functions

Within the body, but above the line beginning with protected void Button1_Click..., enter the following:

private void ShowSquare(double x) => sampLabel.Text += "<br>" + (x * x);

Remember, => is an expression member. It's a function. In other words, it takes the form of a Lambda. At the end of the line, we return x * x. As you can see, this is a very streamlined way of writing functions.

Next, we need to add namespaces. So, after using System, enter the following lines:

using System.Collections.Generic;
using System.Threading;

Now, within the event for the button, we will place the following code list; so, enter this line between a set of curly braces underneath the line beginning with protected void Button1_Click...:

List<double> vals = new List<double>(new double[] { 1, 2, 4, 5, 6, 8 });

In this line, you are making a new list of double data type and then you will initialize it. You can do this a couple of ways, but you can just write an array...