Input string was not in a correct format in double.Parse

Question

I am new to C#. I\'m trying to make a calculator, but the following error occurred:

Input string was not in a correct format.

T

Answer 1

Seems like num2 value should be fetched from textbox2 not textbox1(You are setting textbox1.text to empty and trying to parse it to double again)

//You are setting textbox1 to empty
textBox1.Text = String.Empty;

//here trying to parse it to double
num2 = double.Parse(textBox1.Text);

Also don't use Convert.ToDouble(textBox1.Text) directly. if users type non numeric values your code will crash. first check if its a valid number, always use doube.TryPrase()

double num1;
double.TryParse(textBox1.Text, out num1);