获取哈希表obj键&更改其公共属性

首先声明一个哈希表及其值。哈希表项的键是GUID，值是一个包含几个字符串值的对象。

    Guid g = Guid.NewGuid();
    Hashtable hash = new Hashtable();
    InstallationFiles instFiles = new InstallationFiles(string1, string2, string3);
    hash.Add(g, instFiles);
    //...add many other values with different GUIDs...

我的目标是给用户一个编辑字符串1,string2, string3的可能性。长话短说，我可以获得需要编辑的条目的"GUID g":

   public void edit() 
   {
         //here I retrieve the GUID g of the item which has to be edited:
         object objectHash = item.Tag;
         //here i loop through all hash entries to find the editable one:
         foreach(DictionaryEntry de in hash)
         {
            if(de.Key.ToString() == objectHash) 
            {
            //here I would like to access the selected entry and change string1 - 
           //the line below is not working.
            hash[de.Key].string1 = "my new value"; 
            }
         }
   }

我如何使这行工作?

    hash[de.Key].string1 = "my new value";