Unity保存先パスの指定

現状

外部ファイルで文字列を保存したいのですが、

C#
1    private string DetaPath = Application.dataPath + "/original_data.txt";

このパスを変数に代入するコードを追加した際にエラーが出ました。
このコードを追加したスクリプト全体はこちらです。

using
1using System.Collections.Generic;
2using UnityEngine;
3using System;
4using System.Text;
5using UnityEngine.UI;
6using TMPro;
7using System.IO;
8
9public class Controller : MonoBehaviour {
10    public static bool play;
11    static public int SphereID;
12    static public bool select;
13    static public bool playstart;
14    static public bool HotbarButtonselect;
15    static public Vector2 Pos;
16    static public bool locking;
17    static public int[] hotID = new int[8];
18    static public int writehotID;
19    static public int stage = 1;
20    static public bool Clear;
21    static public bool stop;
22    static public bool stopnow = false;
23    static public bool resumenow =false;
24    [SerializeField]
25    static public float sensitivity = 0.2f;
26    static public bool GameOver;
27    public GameObject FAILED;
28    public GameObject CLEAR;
29    static public bool showCursor;
30    static public bool hideCursor;
31    public Text Pkey_text;
32    static public bool actionnow;
33    static public float nowtimeScale;
34    public TextMeshProUGUI Text_Source;
35    static public string WarningText;
36    static public string TargetScene;
37    public GameObject MenuObj;
38    static public bool OpenTheMenu = false;
39    // Use this for initialization
40    static public bool OpenTheTestData; 
41    static public string GameOverLog;
42    public Text FAILEDInfoText;
43    //DataBase_Start-------------------------------------------------------------------------------------------------------------------------------------
44    public GameObject ConfilmObj;
45    static public List<int> IDData = new List<int>();
46    static public List<Vector3> PositionData = new List<Vector3>();
47    static public List<Quaternion> RotationData = new List<Quaternion>();
48    static public List<GameObject> Targets = new List<GameObject>();
49    static public List<bool> Destroyed = new List<bool>();
50    static public int TotalBlocks;
51    static public bool editOK;
52    public string[] Display_Data = { "_FALIED", "F_AILED", "FA_IELD", "FAI_LED", "FAIL_ED", "FAILE_D", "FAILED_" };
53    private string DataPath = Application.dataPath + "/original_data.txt";
54    string SaveData;
55    //DataBase_End---------------------------------------------------------------------------------------------------------------------------------------
56    // Use this for initialization
57    void Start () {
58        showCursor = false;
59        hideCursor = true;
60        actionnow = false;
61        nowtimeScale = 1;
62        GameOver = false;
63        playstart = false;
64        stop = false;
65        play = false;
66        TotalBlocks = 0;
67        SphereID = 0;
68        select = false;
69        HotbarButtonselect = false;
70        locking = false;
71        Clear = false;
72        StartCoroutine(SwitchText());
73        ImportantSceneButton.ConfilmObj = ConfilmObj;
74        OpenTheTestData = false;
75        editOK = true;
76    }
77
78    // Update is called once per frame
79    void Update()
80    {
81        //Tehon----------------------------------------------------------
82        if (Input.GetKeyDown("t"))
83        {
84            if (OpenTheTestData == false)
85            {
86                editOK = false;
87                OpenTheTestData = true;
88                foreach (GameObject Target in Targets)
89                {
90                    Destroy(Target);
91                }
92            }
93            else
94            {
95                editOK = true;
96                OpenTheTestData = false;
97                for(int i = 0;i <= 100; i++)
98                {
99                    if (Destroyed[i] == false)
100                    {
101                        GameObject Prefab = Instantiate(RayScript.DataObj[IDData[i]], PositionData[i], RotationData[i]) as GameObject;
102                        Prefab.name = Convert.ToString(i);
103                        Targets.Insert(i, Prefab);
104                    }
105                    else
106                    {
107                        Targets.Insert(i, null);
108                    }
109                }
110            }
111        }
112        //Save-----------------------------------------------------
113        if (Input.GetKeyDown("s"))
114        {
115            JSONvar vardatas = new JSONvar();
116            vardatas.IDData = IDData;
117            vardatas.PositionData = PositionData;
118            vardatas.RotationData = RotationData;
119            vardatas.Targets = Targets;
120            vardatas.Destroyed = Destroyed;
121            SaveData = JsonUtility.ToJson(vardatas);
122            Debug.Log(SaveData);
123            File.WriteAllText(DataPath, SaveData, System.Text.Encoding.UTF8);
124        }
125        if (Input.GetKeyDown("o"))
126        {
127            JSONvar roaddata = JsonUtility.FromJson<JSONvar>(SaveData);
128            IDData = roaddata.IDData;
129            PositionData = roaddata.PositionData;
130            RotationData = roaddata.RotationData;
131            Targets = roaddata.Targets;
132            Destroyed = roaddata.Destroyed;
133        }
134        //play----------------------------------------------------
135        if (Input.GetKeyDown("p") && actionnow == false)
136        {
137            if (play == false)
138            {
139                play = true;
140                stop = false;
141                resumenow = true;
142                nowtimeScale = 1;
143                playstart = true;
144                GameObject[] Spawners = GameObject.FindGameObjectsWithTag("Spawner");
145                foreach (GameObject Spawner in Spawners)
146                {
147                    Spawner.GetComponent<Spawn>().Spawner();
148                }
149            }
150            else if (play == true)
151            {
152                ResetGame();
153            }
154        }
155        //menu-----------------------------------------------------------------------
156        if (Input.GetKeyDown("m"))
157        {
158            if (MenuObj.activeSelf)
159            {
160                MenuObj.SetActive(false);
161                hideCursor = true;
162                actionnow = false;
163            }
164            else
165            {
166                MenuObj.SetActive(true);
167                showCursor = true;
168                actionnow = true;
169            }
170        }
171        if (play)
172        {
173            Pkey_text.text = "中断";
174        }
175        else
176        { 
177            Pkey_text.text = "スタート";
178        }
179        if (stopnow && play == true)
180        {
181            stopnow = false;
182            Time.timeScale = 0;
183        }
184        else if (resumenow)
185        {
186            resumenow = false;
187            Time.timeScale = nowtimeScale;
188        }
189        if (showCursor == true)
190        {
191            Cursor.visible = true;
192            Cursor.lockState = CursorLockMode.None;
193            locking = true;
194            showCursor = false;
195        }
196        else if (hideCursor == true)
197        {
198            Cursor.visible = false;
199            Cursor.lockState = CursorLockMode.Locked;
200            locking = false;
201            hideCursor = false;
202        }
203        if(GameOver == true)
204        {
205            FAILED.SetActive(true);
206            Controller.GameOver = true;
207            Controller.showCursor = true;
208            Controller.actionnow = true;
209            FAILEDInfoText.text = GameOverLog;
210        }
211    }
212    public void RetryButton()
213    {
214        FAILED.SetActive(false);
215        CLEAR.SetActive(false);
216        ResetGame();
217        hideCursor = true;
218        GameOver = false;
219        actionnow = false;
220        Clear = false;
221        TotalBlocks = 0;
222        SphereID = 0;
223    }
224
225    void ResetGame()
226    {
227        play = false;
228        GameObject[] destroys = GameObject.FindGameObjectsWithTag("Player");
229        foreach (GameObject destroy in destroys)
230        {
231            Destroy(destroy);
232        }
233        GameObject[] Dummys = GameObject.FindGameObjectsWithTag("Dummy");
234        foreach (GameObject Dummy in Dummys)
235        {
236            Destroy(Dummy);
237        }
238        stop = false;
239        resumenow = true;
240        nowtimeScale = 1;
241        GameObject[] Spawners = GameObject.FindGameObjectsWithTag("Spawner");
242        foreach (GameObject Spawner in Spawners)
243        {
244            Spawner.GetComponent<Spawn>().Reset();
245        }
246    }
247
248    IEnumerator SwitchText()
249    {
250        while (true)
251        {
252            for (int i = 0; i <= Display_Data.Length - 1; i++)
253            {
254                Text_Source.SetText(Display_Data[i]);
255                yield return new WaitForSeconds(1f);
256            }
257        }
258    }
259}
260
261コード

エラーは

UnityException: get_dataPath is not allowed to be called from a MonoBehaviour constructor (or instance field initializer), call it in Awake or Start instead. Called from MonoBehaviour 'Controller' on game object 'GameCon (1)'.
See "Script Serialization" page in the Unity Manual for further details.
Controller..ctor () (at Assets/Scouse/Controller.cs:54)

と

UnityException: get_dataPath is not allowed to be called from a MonoBehaviour constructor (or instance field initializer), call it in Awake or Start instead. Called from MonoBehaviour 'Controller' on game object 'GameCon (1)'.
See "Script Serialization" page in the Unity Manual for further details.
Controller..ctor () (at Assets/Scouse/Controller.cs:54)

が何度も出てきます
書き方に問題があるはずなのですが、何がいけないんでしょうか。
分かる方が見たらすぐわかると思いますが、数時間調べてもわかりませんでした、誰か回答お願いします。