title: How to get mongo TTL to expire in c#
body: <p>Mongo isn't expiring old collections. I checked to make sure my index is type date. </p>
  
  <pre><code>var keys = IndexKeys.Ascending("expiry");
  var options = IndexOptions.SetTimeToLive(TimeSpan.FromMinutes(1));
  
  collection.EnsureIndex(keys, options);
  this.ExpireDate = new BsonDateTime(DateTime.UtcNow.AddMinutes(5));
  var insertResult = collection.Insert(this);
  </code></pre>
  
  <p>Any tips would be gladly appreciated. </p>
  
  <pre><code>[
      {
              "v" : 1,
              "key" : {
                      "_id" : 1
              },
              "ns" : "Showsv1.ShowInfo",
              "name" : "_id_"
      },
      {
              "v" : 1,
              "key" : {
                      "expiry" : 1
              },
              "ns" : "Showsv1.ShowInfo",
              "name" : "expiry_1",
              "expireAfterSeconds" : 60
      }
  </code></pre>
  
  <p>]</p>
  
  <pre><code>"expiry" : ISODate("2013-02-15T02:40:45.876Z")
  </code></pre>