Add code, modify readme.md

Draggable.cs

@@ -0,0 +1,74 @@
+using System;
+using System.Collections.Generic;
+using System.Windows.Forms;
+
+namespace DraggableControls
+{
+    public static class ControlExtension
+    {
+        // TKey is control to drag, TValue is a flag used while dragging
+        private static Dictionary<Control, bool> draggables = 
+                   new Dictionary<Control, bool>();
+        private static System.Drawing.Size mouseOffset;
+ 
+        /// <summary>
+        /// Enabling/disabling dragging for control
+        /// </summary>
+        public static void Draggable(this Control control, bool Enable)
+        {
+            if (Enable)
+            {
+                // enable drag feature
+                if (draggables.ContainsKey(control))
+                {   // return if control is already draggable
+                    return;
+                }
+                // 'false' - initial state is 'not dragging'
+                draggables.Add(control, false);
+ 
+                // assign required event handlersnnn
+                control.MouseDown += new MouseEventHandler(control_MouseDown);
+                control.MouseUp += new MouseEventHandler(control_MouseUp);
+                control.MouseMove += new MouseEventHandler(control_MouseMove);
+            }
+            else
+            {
+                // disable drag feature
+                if (!draggables.ContainsKey(control))
+                {  // return if control is not draggable
+                    return;
+                }
+                // remove event handlers
+                control.MouseDown -= control_MouseDown;
+                control.MouseUp -= control_MouseUp;
+                control.MouseMove -= control_MouseMove;
+                draggables.Remove(control);
+            }
+        }
+
+        static void control_MouseDown(object sender, MouseEventArgs e)
+        {
+            mouseOffset = new System.Drawing.Size(e.Location);
+            // turning on dragging
+            draggables[(Control)sender] = true;
+        }
+
+        static void control_MouseUp(object sender, MouseEventArgs e)
+        {
+            // turning off dragging
+            draggables[(Control)sender] = false;
+        }
+
+        static void control_MouseMove(object sender, MouseEventArgs e)
+        {
+            // only if dragging is turned on
+            if (draggables[(Control)sender] == true)
+            {
+                // calculations of control's new position
+                System.Drawing.Point newLocationOffset = e.Location - mouseOffset;
+                ((Control)sender).Left += newLocationOffset.X;
+                ((Control)sender).Top += newLocationOffset.Y;
+            }
+        }
+    }
+}

README.md

@@ -2,3 +2,12 @@ Control.Draggable
 =================
 
 Makes any WinForms control draggable
+
+Usage
+-----
+
+```csharp
+AnyControl.Draggable(true);
+```
+
+Read more: [Draggable WinForms Controls](http://www.codeproject.com/Tips/178587/Draggable-WinForms-Controls)