private BsonValue VisitValue(Expression expr)
{
// its a constant; Eg: "fixed string"
if (expr is ConstantExpression)
{
var value = expr as ConstantExpression;
return(_mapper.Serialize(value.Type, value.Value, 0));
}
if (expr is MemberExpression && _parameters.Count > 0)
{
var mExpr = (MemberExpression)expr;
var mValue = VisitValue(mExpr.Expression);
var value = mValue.AsDocument[mExpr.Member.Name];
return(_mapper.Serialize(typeof(object), value, 0));
}
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(_mapper.Serialize(typeof(object), getter(), 0));
}
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()));
}
private BsonValue VisitValue(Expression expr)
{
// its a constant; Eg: "fixed string"
if (expr is ConstantExpression)
{
var value = (expr as ConstantExpression).Value;
return(_mapper.Serialize(value));
}
// execute expression
var objectMember = Expression.Convert(expr, typeof(object));
var getterLambda = Expression.Lambda <Func <object> >(objectMember);
var getter = getterLambda.Compile();
return(_mapper.Serialize(getter()));
}
/// <summary>
/// Visit :: x => x.Age + `10` (will create parameter: `p0`, `p1`, ...)
/// </summary>
protected override Expression VisitConstant(ConstantExpression node)
{
MemberExpression prevNode;
var value = node.Value;
// https://stackoverflow.com/a/29708655/3286260
while (_nodes.Count > 0 && (prevNode = _nodes.Peek() as MemberExpression) != null)
{
if (prevNode.Member is FieldInfo fieldInfo)
{
value = fieldInfo.GetValue(value);
}
else if (prevNode.Member is PropertyInfo propertyInfo)
{
value = propertyInfo.GetValue(value);
}
_nodes.Pop();
}
ENSURE(_nodes.Count == 0, "counter stack must be zero to eval all properties/field over object");
var parameter = "p" + (_paramIndex++);
_builder.AppendFormat("@" + parameter);
var type = value?.GetType();
// if type is string, use direct BsonValue(string) to avoid rules like TrimWhitespace/EmptyStringToNull in mapper
var arg = type == null ? BsonValue.Null :
type == typeof(string) ? new BsonValue((string)value) :
_mapper.Serialize(value.GetType(), value);
_parameters[parameter] = arg;
return(node);
}
