ImageForm.cs

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

namespace ImageViewerLite
{
    public partial class ImageForm : Form
    {
        Timer animationTimer;
        const int animSpeed = 10; // In milliseconds

        public ImageForm()
        {
            InitializeComponent();
            animationTimer = new Timer();
            animationTimer.Tick += new EventHandler(animationTimer_Tick);
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            buttonTrayAreaPanel.Location = buttonTray.Location;
            buttonTrayAreaPanel.Size = buttonTray.Size;

            try
            {
                openFileDialog.InitialDirectory = @"H:\Documents\";
            }
            catch
            {
                openFileDialog.InitialDirectory = @"C:\";
            }
        }

        // Other code ambiguous to this issue was cut out

        private void zoomTextBox_KeyUp(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)
            {
                try
                {
                    Zoom(float.Parse(zoomTextBox.Text.Substring(0, zoomTextBox.TextLength - 1)));
                }
                catch (FormatException)
                {
                    Zoom(zoomTextBox.Text);
                }
                _image.Focus();
            }

        }

        private void Zoom(float percent)
        {
            _image.Zoom = percent * 0.01;

            CenterImage();
        }
        private void Zoom(string level)
        {
            if (level.ToLower() == "fit")
            {

            }
            else if (level.ToLower() == "full")
            {
                _image.Zoom = 1;
            }

            CenterImage();
        }

        private void CenterImage()
        {
            Point halfSize = new Point(_image.Image.Size.Width / 2, _image.Image.Size.Height / 2);
            Point center = new Point(this.Width / 2, this.Height / 2);

            _image.Location = new Point(center.X - halfSize.X, center.Y - halfSize.Y);
        }

        private void zoomTextBox_TextChanged(object sender, EventArgs e)
        {
            try
            {
                zoomUpDown.Value = decimal.Parse(zoomTextBox.Text);
            }
            catch
            {
                zoomUpDown.Value = (decimal)_image.Zoom;
            }
        }

        private void zoomUpDown_ValueChanged(object sender, EventArgs e)
        {
            zoomTextBox.Text = zoomUpDown.Value.ToString();
            Zoom(float.Parse(zoomTextBox.Text));
        }
    }
}