title: Lambda expression not working with MongoDb C# Driver 1.4
body: <p>I have updated my project with the MongoDb C# Driver 1.4 and one of my Lambda expression is not working anymore.</p>
  
  <p>Before I was using MongoDb C# Driver 1.3.1 with Fluent Mongo to support Linq.</p>
  
  <p>Here is my method:</p>
  
  <pre><code>IQueryable&lt;T&gt; IBackend&lt;T&gt;.Get(System.Linq.Expressions.Expression&lt;Func&lt;T, bool&gt;&gt; expression)
  {
      return collection.AsQueryable&lt;T&gt;().Where(expression);
  }
  </code></pre>
  
  <p>This lambda expression works:</p>
  
  <pre><code>var addedCustomer = repo.Get(c =&gt; c.FirstName == "Elwood").SingleOrDefault();
  </code></pre>
  
  <p>This one now throws an exception:</p>
  
  <pre><code>var updatedCustomer = repo.Get(c =&gt; c.Id == customer.Id).SingleOrDefault();
  </code></pre>
  
  <p>Thrown exception message:</p>
  
  <pre><code>Object reference not set to an instance of an object.
  </code></pre>
  
  <p>Update here is my stacktrace:</p>
  
  <pre><code>MongoDB.Bson.dll!MongoDB.Bson.Serialization.BsonClassMapSerializer.GetMemberSerializationInfo(string memberName) Line 253 + 0x3 bytes   C#
  MongoDB.Driver.dll!MongoDB.Driver.Linq.SelectQuery.GetSerializationInfoMember(MongoDB.Bson.Serialization.IBsonSerializer serializer, System.Linq.Expressions.MemberExpression memberExpression) Line 962 + 0xc bytes    C#
  MongoDB.Driver.dll!MongoDB.Driver.Linq.SelectQuery.GetSerializationInfo(MongoDB.Bson.Serialization.IBsonSerializer serializer, System.Linq.Expressions.Expression expression) Line 888 + 0xf bytes  C#
  MongoDB.Driver.dll!MongoDB.Driver.Linq.SelectQuery.GetSerializationInfo(System.Linq.Expressions.Expression expression) Line 880 + 0xf bytes C#
  MongoDB.Driver.dll!MongoDB.Driver.Linq.SelectQuery.BuildComparisonQuery(System.Linq.Expressions.BinaryExpression binaryExpression) Line 433 + 0x1f bytes    C#
  MongoDB.Driver.dll!MongoDB.Driver.Linq.SelectQuery.BuildQuery(System.Linq.Expressions.Expression expression) Line 768 + 0x37 bytes  C#
  MongoDB.Driver.dll!MongoDB.Driver.Linq.SelectQuery.BuildQuery() Line 113 + 0xc bytes    C#
  MongoDB.Driver.dll!MongoDB.Driver.Linq.SelectQuery.Execute() Line 122 + 0x9 bytes   C#
  MongoDB.Driver.dll!MongoDB.Driver.Linq.MongoQueryProvider.Execute(System.Linq.Expressions.Expression expression) Line 147 + 0xb bytes   C#
  MongoDB.Driver.dll!MongoDB.Driver.Linq.MongoQueryProvider.Execute&lt;Lion.Tools.Tests.Backends.Entities.Customer&gt;(System.Linq.Expressions.Expression expression) Line 131 + 0xc bytes  C#
  [External Code] 
  Lion.Tools.Tests.dll!Lion.Tools.Tests.Backends.MongoDbBackendTests.MongoDb_Can_Add_Select_And_Update_Test() Line 79 + 0x27f bytes   C#
  [External Code] 
  </code></pre>
  
  <p>Any idea on what's going wrong?</p>
  
  <p>Thanks</p>