Here are (quite a few) extensions that are just quick little pieces of code that you'll probably need and it's no pain to implement, but it makes your code that much harder to read. Now with useful methods like Browse(), Save(), and validation methods! It's missing XML documentation, though

Code:
using System;
using System.Runtime.CompilerServices;
using System.Windows.Forms;
using System.Drawing;
using System.Collections.Generic;

namespace YAMStudio_TD_Maker {
    public static class Extensions {
        private static Dictionary<Control, Dictionary<string, object>> dict = new Dictionary<Control, Dictionary<string, object>>();
        // File browsing
        public static DialogResult Browse(this Control t, string filter) {
            OpenFileDialog openDialog = new OpenFileDialog();
            openDialog.Filter = filter;
            DialogResult result = openDialog.ShowDialog();
            if (result == DialogResult.OK) t.Text = openDialog.FileName;
            return result;
        }
        public static DialogResult Browse(this Control t) {
            return t.Browse("All Files|*.*");
        }
        
        // Saving
        public static void Save(this TextBox t, string filePath) {
            System.IO.File.WriteAllText(filePath, t.Text);
        }

        // Validation
        public static void MustMatch(this TextBox t, string regexPattern, string errorMessage) {
            t.Leave += (object sender, EventArgs e) => {
                Label x = null;
                if (!System.Text.RegularExpressions.Regex.IsMatch(t.Text, regexPattern)) {
                    if (t.PopInformation<Label>("ErrorTag") == null && t.Parent != null) {
                        Label l = new Label();
                        l.Location = new Point(t.Location.X+t.Width+2,t.Location.Y);
                        l.Text = errorMessage;
                        l.ForeColor = Color.Red;
                        t.PushInformation("ErrorTag", l);
                        t.Parent.Controls.Add(l);
                    }
                    t.Focus();
                } else if ((x = t.PopInformation<Label>("ErrorTag")) != null && t.Parent != null ) {
                    t.Parent.Controls.Remove(x);
                }
            };
        }
        public static void MustMatch(this TextBox t, string regexPattern) {
            t.MustMatch(regexPattern, "Invalid value.");
        }
        public static void Integer(this TextBox t, string errorMessage) {
            t.Leave += (object sender, EventArgs e) => {
                Label x = null;
                int pval = 0;
                if (t.Text == "" || !int.TryParse(t.Text, out pval)) {
                    if (t.PopInformation<Label>("ErrorTag") == null && t.Parent != null) {
                        Label l = new Label();
                        l.Location = new Point(t.Location.X+t.Width+2,t.Location.Y);
                        l.Text = errorMessage;
                        l.ForeColor = Color.Red;
                        t.PushInformation("ErrorTag", l);
                        t.Parent.Controls.Add(l);
                    }
                    t.Focus();
                } else if ((x = t.PopInformation<Label>("ErrorTag")) != null && t.Parent != null ) {
                    t.Parent.Controls.Remove(x);
                }
            };
        }
        public static void Integer(this TextBox t) {
            t.Integer("Please enter a valid number.");
        }

        // Information storage
        public static void PushInformation(this Control c, string key, object value) {
            if (!dict.ContainsKey(c)) dict.Add(c, new Dictionary<string, object>());
            dict[c].Add(key, value);
        }

        public static T PopInformation<T>(this Control c, string key) {
            if (!dict.ContainsKey(c)) return default(T);
            if (!dict[c].ContainsKey(key)) return default(T);
            return (T)dict[c][key];
        }

        // Disable content
        public static void ToggleContent(this Control c, bool enabled) {
            foreach (Control x in c.Controls) x.Enabled = enabled;
        }

        // Get content
        public static RadioButton GetCheckedRadioButton(this Control c) {
            foreach (Control x in c.Controls) {
                if (x is RadioButton) {
                    RadioButton r = (RadioButton)x;
                    if (r.Checked) return r;
                }
            }
            return null;
        }

        // OK/Cancel dialog buttons
        public static void OK(this Button b) {
            if (b.Parent is Form) {
                Form f = (Form)b.Parent;
                b.Click += (object sender, EventArgs e) => {
                    f.DialogResult = DialogResult.OK;
                    f.Close();
                };
            } else {
                throw new ArgumentException("Button's parent must be of type System.Windows.Form.");
            }
        }
        public static void Cancel(this Button b) {
            if (b.Parent is Form) {
                Form f = (Form)b.Parent;
                b.Click += (object sender, EventArgs e) => {
                    f.DialogResult = DialogResult.Cancel;
                    f.Close();
                };
            } else {
                throw new ArgumentException("Button's parent must be of type System.Windows.Form.");
            }
        }
    }
}