namespace ConsoleApplication
{
    using System;
    using System.Linq;

    using MongoDB.Bson.Serialization.Serializers;
    using MongoDB.Driver;

    class Program
    {
        static void Main(string[] args)
        {
            MongoDB.Bson.Serialization.BsonSerializer.RegisterSerializer(typeof(DateTime), new DateTimeSerializer(DateTimeKind.Local));
            MongoDB.Bson.Serialization.BsonSerializer.RegisterSerializer(typeof(DateTime?), new DateTimeSerializer(DateTimeKind.Local));

            new MongoClient("mongodb://localhost/testdb")
                .GetDatabase("testdb")
                .GetCollection<TestItem>(typeof(TestItem).Name)
                .AsQueryable()
                .Count(e => e.Date == null);
        }
    }
    
    public sealed class TestItem
    {
        public Guid Id { get; set; }
        
        public DateTime? Date { get; set; }
    }
}

An unhandled exception of type 'System.InvalidOperationException' occurred in System.Core.dll

Additional information: The operands for operator 'Equal' do not match the parameters of method 'op_Equality'.

   at System.Linq.Expressions.Expression.GetMethodBasedBinaryOperator(ExpressionType binaryType, Expression left, Expression right, MethodInfo method, Boolean liftToNull)
   at System.Linq.Expressions.Expression.Equal(Expression left, Expression right, Boolean liftToNull, MethodInfo method)
   at System.Linq.Expressions.Expression.MakeBinary(ExpressionType binaryType, Expression left, Expression right, Boolean liftToNull, MethodInfo method, LambdaExpression conversion)
   at System.Linq.Expressions.BinaryExpression.Update(Expression left, LambdaExpression conversion, Expression right)
   at System.Linq.Expressions.ExpressionVisitor.VisitBinary(BinaryExpression node)
   at MongoDB.Driver.Linq.Processors.SerializationBinder.VisitBinary(BinaryExpression node)
   at System.Linq.Expressions.BinaryExpression.Accept(ExpressionVisitor visitor)
   at MongoDB.Driver.Linq.Processors.SerializationBinder.Visit(Expression node)
   at MongoDB.Driver.Linq.Processors.PipelineBindingContext.Bind(Expression node)
   at MongoDB.Driver.Linq.Processors.BinderHelper.BindWhere(PipelineExpression pipeline, IBindingContext bindingContext, LambdaExpression lambda)
   at MongoDB.Driver.Linq.Processors.Pipeline.MethodCallBinders.CountBinder.Bind(PipelineExpression pipeline, PipelineBindingContext bindingContext, MethodCallExpression node, IEnumerable`1 arguments)
   at MongoDB.Driver.Linq.Processors.MethodInfoMethodCallBinder`1.Bind(PipelineExpression pipeline, TBindingContext bindingContext, MethodCallExpression node, IEnumerable`1 arguments)
   at MongoDB.Driver.Linq.Processors.PipelineBinderBase`1.BindMethodCall(MethodCallExpression node)
   at MongoDB.Driver.Linq.Processors.PipelineBinderBase`1.Bind(Expression node)
   at MongoDB.Driver.Linq.Processors.Pipeline.PipelineBinder.Bind(Expression node, IBsonSerializerRegistry serializerRegistry)
   at MongoDB.Driver.Linq.MongoQueryProviderImpl`1.Prepare(Expression expression)
   at MongoDB.Driver.Linq.MongoQueryProviderImpl`1.Translate(Expression expression)
   at MongoDB.Driver.Linq.MongoQueryProviderImpl`1.Execute(Expression expression)
   at MongoDB.Driver.Linq.MongoQueryProviderImpl`1.Execute[TResult](Expression expression)
   at System.Linq.Queryable.Count[TSource](IQueryable`1 source, Expression`1 predicate)
   at ConsoleApplication11.Program.Main(String[] args) in c:\users\gushin\documents\visual studio 2015\Projects\ConsoleApplication11\ConsoleApplication11\Program.cs:line 16
   at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
   at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()