private BsonValue VisitValue(Expression expr, Expression left)
{
// check if left side is an enum and convert to string before return
Func <Type, object, BsonValue> convert = (type, value) =>
{
var enumType = (left as UnaryExpression) == null ? null : (left as UnaryExpression).Operand.Type;
if (enumType != null && enumType.GetTypeInfo().IsEnum)
{
var str = Enum.GetName(enumType, value);
return(_mapper.Serialize(typeof(string), str, 0));
}
return(_mapper.Serialize(type, value, 0));
};
// its a constant; Eg: "fixed string"
if (expr is ConstantExpression)
{
var value = (expr as ConstantExpression);
return(convert(value.Type, value.Value));
}
else if (expr is MemberExpression && _parameters.Count > 0)
{
var mExpr = (MemberExpression)expr;
var mValue = this.VisitValue(mExpr.Expression, left);
var value = mValue.AsDocument[mExpr.Member.Name];
return(convert(typeof(object), value));
}
else if (expr is ParameterExpression)
{
BsonValue result;
if (_parameters.TryGetValue((ParameterExpression)expr, out result))
{
return(result);
}
}
// execute expression
var objectMember = Expression.Convert(expr, typeof(object));
var getterLambda = Expression.Lambda <Func <object> >(objectMember);
var getter = getterLambda.Compile();
return(convert(typeof(object), getter()));
}