Unity : How to in code create / delete / check for existence of tags and layers ?

TagsAndLayers.cs

using UnityEditor;
using UnityEngine;
using System;

using System.Collections;
using System.Collections.Generic;
using System.Linq;

namespace Cosmos
{
    public static class TagsAndLayers
    {
        private static int maxTags = 10000;
        private static int maxLayers = 31;

        //Return true, if tag was added, false otherwise.
        public static bool AddNewTag(string tagName)
        {
            // Open tag manager
            SerializedObject tagManager = new SerializedObject(AssetDatabase.LoadAllAssetsAtPath("ProjectSettings/TagManager.asset")[0]);
            // Tags Property
            SerializedProperty tagsProp = tagManager.FindProperty("tags");
            if (tagsProp.arraySize >= maxTags)
            {
                Debug.Log("No more tags can be added to the Tags property. You have " + tagsProp.arraySize + " tags");
                return false;
            }
            // if not found, add it
            if (!PropertyExists(tagsProp, 0, tagsProp.arraySize, tagName))
            {
                int index = tagsProp.arraySize;
                // Insert new array element
                tagsProp.InsertArrayElementAtIndex(index);
                SerializedProperty sp = tagsProp.GetArrayElementAtIndex(index);
                // Set array element to tagName
                sp.stringValue = tagName;
                Debug.Log("Tag: " + tagName + " has been added");
                // Save settings
                tagManager.ApplyModifiedProperties();

                return true;
            }
            else
            {
                //Debug.Log ("Tag: " + tagName + " already exists");
            }
            return false;
        }

        private static bool PropertyExists(SerializedProperty property, int start, int end, string value)
        {
            for (int i = start; i < end; i++)
            {
                SerializedProperty t = property.GetArrayElementAtIndex(i);
                if (t.stringValue.Equals(value))
                {
                    return true;
                }
            }
            return false;
        }

        //returns true, if tag was removed, false otherwise.
        public static bool RemoveTag(string tagName)
        {

            // Open tag manager
            SerializedObject tagManager = new SerializedObject(AssetDatabase.LoadAllAssetsAtPath("ProjectSettings/TagManager.asset")[0]);

            // Tags Property
            SerializedProperty tagsProp = tagManager.FindProperty("tags");

            if (PropertyExists(tagsProp, 0, tagsProp.arraySize, tagName))
            {
                SerializedProperty sp;

                for (int i = 0, j = tagsProp.arraySize; i < j; i++)
                {

                    sp = tagsProp.GetArrayElementAtIndex(i);
                    if (sp.stringValue == tagName)
                    {
                        tagsProp.DeleteArrayElementAtIndex(i);
                        Debug.Log("Tag: " + tagName + " has been removed");
                        // Save settings
                        tagManager.ApplyModifiedProperties();
                        return true;
                    }

                }
            }

            return false;

        }


        /// Checks to see if tag exists.
        /// <returns><c>true</c>, if tag exists, <c>false</c> otherwise.</returns>
        public static bool TagExists(string tagName)
        {
            // Open tag manager
            SerializedObject tagManager = new SerializedObject(AssetDatabase.LoadAllAssetsAtPath("ProjectSettings/TagManager.asset")[0]);

            // Layers Property
            SerializedProperty tagsProp = tagManager.FindProperty("tags");
            return PropertyExists(tagsProp, 0, maxTags, tagName);
        }

        /// Adds the layer.
        /// <returns><c>true</c>, if layer was added, <c>false</c> otherwise.</returns>
        public static bool AddNewLayer(string layerName)
        {
            // Open tag manager
            SerializedObject tagManager = new SerializedObject(AssetDatabase.LoadAllAssetsAtPath("ProjectSettings/TagManager.asset")[0]);
            // Layers Property
            SerializedProperty layersProp = tagManager.FindProperty("layers");
            if (!PropertyExists(layersProp, 0, maxLayers, layerName))
            {
                SerializedProperty sp;
                // Start at layer 9th index -> 8 (zero based) => first 8 reserved for unity / greyed out
                for (int i = 8, j = maxLayers; i < j; i++)
                {
                    sp = layersProp.GetArrayElementAtIndex(i);
                    if (sp.stringValue == "")
                    {
                        // Assign string value to layer
                        sp.stringValue = layerName;
                        Debug.Log("Layer: " + layerName + " has been added");
                        // Save settings
                        tagManager.ApplyModifiedProperties();
                        return true;
                    }
                    if (i == j)
                        Debug.Log("All allowed layers have been filled");
                }
            }
            else
            {
                //Debug.Log ("Layer: " + layerName + " already exists");
            }
            return false;
        }

        public static string NewLayer(string name)
        {
            if (name != null || name != "")
            {
                AddNewLayer(name);
            }

            return name;
        }

        /// Removes the layer.
        /// <returns><c>true</c>, if layer was removed, <c>false</c> otherwise.</returns>
        public static bool RemoveLayer(string layerName)
        {

            // Open tag manager
            SerializedObject tagManager = new SerializedObject(AssetDatabase.LoadAllAssetsAtPath("ProjectSettings/TagManager.asset")[0]);

            // Tags Property
            SerializedProperty layersProp = tagManager.FindProperty("layers");

            if (PropertyExists(layersProp, 0, layersProp.arraySize, layerName))
            {
                SerializedProperty sp;

                for (int i = 0, j = layersProp.arraySize; i < j; i++)
                {

                    sp = layersProp.GetArrayElementAtIndex(i);

                    if (sp.stringValue == layerName)
                    {
                        sp.stringValue = "";
                        Debug.Log("Layer: " + layerName + " has been removed");
                        // Save settings
                        tagManager.ApplyModifiedProperties();
                        return true;
                    }

                }
            }

            return false;

        }

        /// Checks to see if layer exists.
        /// <returns><c>true</c>, if layer exists, <c>false</c> otherwise.</returns>
        public static bool LayerExists(string layerName)
        {
            // Open tag manager
            SerializedObject tagManager = new SerializedObject(AssetDatabase.LoadAllAssetsAtPath("ProjectSettings/TagManager.asset")[0]);

            // Layers Property
            SerializedProperty layersProp = tagManager.FindProperty("layers");
            return PropertyExists(layersProp, 0, maxLayers, layerName);
        }



    }

}