Logic error behind converting distance in C#

Application: I am trying to convert one type of distance to another when the user inputs the data. However, my output for inches to yards and inches to feet is giving me logic errors of 0 instead of the desire calculation. Feet to yards is not giving me any output and yards to yards is doing the same thing. I have been trying to figure it out for 2 hours and can't seem to understand. The syntax is correct and the logic is the same as the other desire output.

My code:

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 Distance_Converter
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void ConvertButton_click(object sender, EventArgs e)
        {
            int distance_to_convert;
            string lengthOption1;
            string lengthOption2;
            int feet = 12; 




            lengthOption1 = FromListBox.SelectedItem.ToString();

            distance_to_convert = int.Parse(distancetoconvertTextBox.Text);

            if ((FromListBox.SelectedIndex) != 1 && (ToListBox.SelectedIndex) != -1)

                lengthOption1 = FromListBox.SelectedItem.ToString();
                lengthOption2 = ToListBox.SelectedItem.ToString();
            {
                switch (lengthOption1)
                {
                    case "Inches":
                        if (lengthOption2 == "Inches")
                        {
                            ConvertedDistanceTextBox.Text = distance_to_convert.ToString();
                        }
                        else if (lengthOption2 == "Feet")
                        {
                            int inches_feet = distance_to_convert / feet;
                            //int feet = 12; 
                            ConvertedDistanceTextBox.Text = inches_feet.ToString();
                        }
                        else if (lengthOption2 == "Yards")
                        {
                            int inches_yard = distance_to_convert / 36;
                            ConvertedDistanceTextBox.Text = inches_yard.ToString();
                        }
                        break;
                    case "Feet":
                        if (lengthOption2 == "Inches")
                        {
                            int feet_inches = distance_to_convert * 12;
                            ConvertedDistanceTextBox.Text = feet_inches.ToString();
                        }
                        else if (lengthOption2 == "Feet")
                        {
                            ConvertedDistanceTextBox.Text = distance_to_convert.ToString(); ;
                        }
                        else if (lengthOption2 == "Yards")
                        {
                            float  feet_yard = distance_to_convert / 3;
                            ConvertedDistanceTextBox.Text = feet_yard.ToString();
                        }
                        break;

                    case "Yards":
                        if (lengthOption2 == "Inches")
                        {
                            int Yards_inches = distance_to_convert * 36;
                            ConvertedDistanceTextBox.Text = Yards_inches.ToString();
                        }
                        else if (lengthOption2 == "Feet")
                        {
                            int Yards_feet = distance_to_convert * 3;
                            ConvertedDistanceTextBox.Text = Yards_feet.ToString();
                        }
                        else if (lengthOption2 == "Yards")
                        {
                            ConvertedDistanceTextBox.Text = distance_to_convert.ToString(); ;
                        }
                        break;
                }
            }

        }
        private void Exitbutton_click(object sender, EventArgs e)
        {
            this.Close();
        }
    }
}