mongodb repository inc operation using offical mongodb Driver, using Linq Expression Extension

gistfile1.txt

public void Inc(Expression<Func<T, bool>> predicate, Expression<Func<T, T>> updateExpression) 
{
    var propertyNamesAndValues = new Dictionary<string, int>();

    var query = ((MongoQueryable<T>)this.collection.AsQueryable<T>().Where(predicate)).GetMongoQuery();

    var memberInitExpression = (MemberInitExpression)updateExpression.Body;
    if (memberInitExpression == null)
        throw new ArgumentException("The update expression must be of type MemberInitExpression.", "updateExpression");


    foreach (MemberBinding binding in memberInitExpression.Bindings)
    {
        var memberAssignment = binding as MemberAssignment;
        if (memberAssignment == null)
            throw new ArgumentException("The update expression MemberBinding must only by type MemberAssignment.", "updateExpression");

        Expression memberExpression = memberAssignment.Expression;

        ParameterExpression parameterExpression = null;
        memberExpression.Visit((ParameterExpression p) =>
        {
            parameterExpression = p;
            return p;
        });


        if (parameterExpression == null)
        {
            object value;

            if (memberExpression.NodeType == ExpressionType.Constant)
            {
                var constantExpression = memberExpression as ConstantExpression;
                if (constantExpression == null)
                    throw new ArgumentException(
                        "The MemberAssignment expression is not a ConstantExpression.", "updateExpression");

                value = constantExpression.Value;
            }
            else
            {
                LambdaExpression lambda = Expression.Lambda(memberExpression, null);
                value = lambda.Compile().DynamicInvoke();
            }

            if (value != null)
            {
                propertyNamesAndValues.Add(binding.Member.Name, Convert.ToInt32(value));
            }
            else
            {
                propertyNamesAndValues.Add(binding.Member.Name, Convert.ToInt32(value));
            }
        }
    }
    var update = new UpdateBuilder();
    foreach (var kv in propertyNamesAndValues)
    {
        update.Inc(kv.Key, kv.Value);
    }
     
    this.collection.Update(query, update);
}