title: Saving List of strings modifiable by user
body: <p>I am trying to store a number of categories that will be used to populate a drop down list however I would like to have some base categories stored somewhere (been trying app.config) but then to also allow the user to add/remove categories as they require.</p>
  
  <p>I've read a lot of information about the custom ConfigurationSection with a ConfigurationElementCollection but couldn't wrap my head around it. I ended up going with the delimited value option and using Split:</p>
  
  <pre><code>&lt;appSettings&gt;
      &lt;add key="categories" value="Work;Education;Taxes;Medical"/&gt;
  &lt;/appSettings&gt;
  </code></pre>
  
  <p>I then tried to do the following which I also found online:</p>
  
  <pre><code>string categories = ConfigurationManager.AppSettings.Get("categories");
  ConfigurationManager.AppSettings.Remove("categories");
  ConfigurationManager.AppSettings.Add("categories", categories + ";Test");
  </code></pre>
  
  <p>But get the error that it is Read Only.</p>
  
  <p>My question is, what is the normal way to achieve something like this where a list of elements for a control like a combo box is stored in some config that can be read and modified?</p>