c# - Nested Internal Class with Readonly Hashtable throws Null ref exception.. on assignment -

in internal game class, have both a) defined nested internal gamertags class , b) defined gamertags[] _array variable.

in internal gamertags class (the nested class, simplicity left out) have readonly hashtable. after initialization, still null ref exception when try assign value. i'm not changing pointer value only, need add initialization hastable?

internal class gamertags     {         private readonly hashtable _privatereadonlyhashtable;         private string _json;         private string _hash;          internal idictionary privatereadonlyhashtable         {                         {                 return this._privatereadonlyhashtable;             }         }          internal string hash         {                         {                 this.ensurehash();                 return this._hash;             }         }                     internal object this[string key]         {                         {                 return this._privatereadonlyhashtable[key];             }             set //throws exception             {                 this._privatereadonlyhashtable[key] = value;             }         }          internal string json         {                         {                 if (string.isnullorempty(this._json))                 {                     this._json = myjsonserializer.serialize(this._privatereadonlyhashtable);                 }                 return this._json;             }         }          internal int x         {             get;             private set;         }          internal int y         {             get;             private set;         }          internal gamertags(int x, int y)         {             this.x = x;             this.y = y;         }          private void ensurehash()         {             bool flag = false;             if (string.isnullorempty(this._hash))             {                 if (flag)                 {                     if (this.json.length < 100)                     {                         this._hash = this.json;                         return;                     }                     byte[] bytes = encoding.ascii.getbytes(this.json);                     byte[] numarray = (new sha1cryptoserviceprovider()).computehash(bytes);                     this._hash = convert.tobase64string(numarray);                     return;                 }                 this._hash = this.fasthash();             }         }          private string fasthash()         {             stringbuilder stringbuilder = new stringbuilder();             foreach (string key in this._privatereadonlyhashtable.keys)             {                 stringbuilder.append(key);                 stringbuilder.append("_");                 stringbuilder.append(this._privatereadonlyhashtable[key]);                 stringbuilder.append("_");             }             return stringbuilder.tostring();         }     } } 

server error in '/' application.

object reference not set instance of object. description: unhandled exception occurred during execution of current web request. please review stack trace more information error , originated in code.

exception details: system.nullreferenceexception: object reference not set instance of object.

init , assignment

        int = 2; int b = 0;         gamertags gamertag = new game.gamertags(a, b);         gamertag["fuel"] = "loaded";              //throws exception         gamertag["enginestatus"] = (boolisiton ? 1 : 0); //throw exception 

indeed need instantiate _privatereadonlyhashtable field.

internal class gamertags {     private readonly hashtable _privatereadonlyhashtable =  new hashtable();      ..     .. }