C# :: How To Add Keyboard And Button Press To A Program

I have a problem where I need to add the ability to input numbers into a calculator program through either a form button press or keyboard press. I have the button press working fine though I can't seem to get the program to start with the cursor active in the textbox for keyboard input. I've use this.ActiveControl = result; "result" being the textbox. Though the issue here is the program starts off with the cursor active but only for the first instance of keyboard inputs.

Perhaps its the way I wrote the program but is there a way I can achieve this? I found a way to write this calc by having a single event for all button presses, opposed from an event for 1-9. Not sure if this is a good approach but here is some of the code.

private double num = 0;
private string calculate;
bool pressed = false;
private void button_Click(object sender, EventArgs e) {
if ((result.Text == "0")||(pressed == true)) {

[Code] ....