title: Object must implement IConvertible in C#
body: <p>I get info of coinmarketcap api in C# and store in database but when try get &quot;percent_change_90d&quot; and write in my application get this error:</p>
  <blockquote>
  <p>Object must implement IConvertible</p>
  </blockquote>
  <p><a href="https://pro-api.coinmarketcap.com/v1/cryptocurrency/listings/latest?CMC_PRO_API_KEY=e0d277bb-ed26-4ed6-b198-dc67cbf48770&amp;start=1&amp;limit=5000" rel="nofollow noreferrer">https://pro-api.coinmarketcap.com/v1/cryptocurrency/listings/latest?CMC_PRO_API_KEY=e0d277bb-ed26-4ed6-b198-dc67cbf48770&amp;start=1&amp;limit=5000</a></p>
  <p>This is my C# code:</p>
  <pre><code>itm.PercentChnage90D = item[&quot;quote&quot;][&quot;USD&quot;][&quot;percent_change_90d&quot;].Value&lt;double?&gt;();
  
  public class CoinData
  {
      public string CoinId;
      public string CoinName;
      public string CoinSymbol;
      public double PriceUsd;
      public double PriceBtc;
      public double? PercentChnage1H;
      public double? PercentChnage24H;
      public double? PercentChnage7D;
      public double? PercentChnage30D;
      public double? PercentChnage60D;
      public double? PercentChnage90D;
      public double? Volume24H;
      public double? Circulating_supply;
  }
  </code></pre>
  <p>How fix this issue? Thanks</p>