How do I solve a BuildAssetBundles Compilation Error that only occurs in the Editor?

Greetings,

I'm running Unity 5.5.0f3 personal on Windows 10, 64 bit, and I'm trying to build an AssetBundle for a simple project. Here's the script I derived from the BuildPipeline BuildAssetBundles documentation:

 using UnityEngine;
 using UnityEditor;
 
 /// <summary>
 /// Builds the asset bundle
 /// Code below is based on the Unity Scripting Reference documentation for the
 /// BuildPipeline BuildAssetBundles method
 /// </summary>
 public class BuildAssetBundle : MonoBehaviour {
 
     /// <summary> 
     /// Adds a menu item to build the asset bundle
     /// </summary>
     [MenuItem("Asset Bundle/Build Asset Bundle")]
     static void BuildAB() {​
 
         // Put the bundle in a folder called "AssetBundle"
         BuildPipeline.BuildAssetBundles("Assets/AssetBundle",
             BuildAssetBundleOptions.None,
             BuildTarget.StandaloneWindows);​
     }​
 }
  

This code compiles fine in Visual Studio with no errors (and I've confirmed there's an assembly reference to the UnityEditor dll in the Visual Studio project).

When I select Asset Bundle > Build Asset Bundle from the menu bar in the Unity editor, I get error messages in the Console pane that say

 The type or namespace name `UnityEditor' could not be found. Are you missing an assembly reference?
 Error building Player because scripts had compiler errors

Any ideas how I can fix this so I can build my Asset Bundle in the editor?

Thanks in advance for any suggestions.