using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace CalcTwo
{
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();

    }


    string input = string.Empty;
    double numb1, numb2, result;


    private void button1_Click(object sender, EventArgs e)
    {
        double.TryParse(textBox1.Text, out numb1);
        double.TryParse(textBox2.Text, out numb2);
        result = numb1 + numb2;
        textBox3.Text = result.ToString();
    }

    private void button4_Click(object sender, EventArgs e)
    {
        double.TryParse(textBox1.Text, out numb1);
        double.TryParse(textBox2.Text, out numb2);
        result = numb1 - numb2;
        textBox3.Text = result.ToString();
    }
}
}

private void CaptureValues()
{
    double.TryParse(textBox1.Text, out numb1);
    double.TryParse(textBox2.Text, out numb2);
}

private void button1_Click(object sender, EventArgs e)
{
    CaptureValues();
    result = numb1 + numb2;
    textBox3.Text = result.ToString();
}

private void CaptureValues()
{
    if (!double.TryParse(textBox1.Text, out numb1))
        // textBox1 couldn't be parsed, show an error message
    if (!double.TryParse(textBox2.Text, out numb2))
        // textBox2 couldn't be parsed, show an error message
}

private double Value1
{
    get
    {
        double result;
        if (!double.TryParse(textBox1.Text, out result))
            throw new Exception("Couldn't parse the first text box!");
        return result;
    }
}

private double Value2
{
    get
    {
        double result;
        if (!double.TryParse(textBox2.Text, out result))
            throw new Exception("Couldn't parse the second text box!");
        return result;
    }
}

textBox3.Text = (Value1 + Value2).ToString();

try
{
    textBox3.Text = (Value1 + Value2).ToString();
}
catch (Exception ex)
{
    // examine what happened with ex and show an error
}