Alex (Xtensive) wrote:

1) It's a bad idea to use DirectSqlAccessor here. LINQ is definitely better, since you shouldn't care about the mapping. You should just build the query (expression tree there) dynamically.

Just yesterday we've added quite useful version of Query.All method: Query.All(Type entityType). It can be used with dynamic query for exactly such cases:

var entityType = typeof (AnyEntityType); // i.e. type is defined in runtime
var query =  Query.All(type).Select("new(TextField as TextField, ValueField as ValueField)"); // dynamic condition

// Let's perform query and cast the result to static type we know
var result = new List<KeyValuePair<string,string>>();
foreach (dynamic d in query)
  result.Add(new KeyValuePair<string,string>(d.TextField, d.ValueField);

2) You can acquire all the mapping information using entity.TypeInfo property (TypeInfo object). All TypeInfo objects describing persistent types are available via Domain.Model.Types collection.

mahdness wrote:

Ok, now we're talking about something really interesting.

1) Query.All() This was pretty easy to implement ourselves with typeof(Query).GetMethod("All", BindingFlags.Static).MakeGenericType(entityType) But good anyway.

2) Select("new(TextField as TextField.....") So, if I have a Customer entity with fields (Name, PhoneNumber, AssignedTo) where AssignedTo is of type Employee, and Employee has fields (Name, Salary), can I do:

Query.All(typeof(Customer)).Select("new(Name, PhoneNumber, AssignedTo, AssignedTo.Name, AssignedTo.Salary)")

Or how am I supposed to do that? And what if I have a type I'd like to project it to (i.e. if I do NOT want to use anonymous types)?

3) What's the best practice for implementing a Where(...) clause? Using Dynamic LINQ? Or have you developed another option?

4) Prefetching In #2 above, will the query automatically prefetch the required fields (namely AssignedTo.Name and AssignedTo.Salary from the referenced Employee type)? If not, how can we specify prefetch?

Thanks guys!

Alex (Xtensive) wrote:

2 hannankhanji:

Use either domain.Model.Types[string shortTypeName] or domain.Model.Types.Find(string fullTypeName) methods to get TypeInfo object (our persistent type model).

TypeInfo.UnderlyingType is .NET Type object corresponding to it.

I forgot to mention that changes related to Query.All(Type type) aren't available yet (will be available in the nearest update).

2 mahdness:

> This was pretty easy to implement ourselves

Almost true: our LINQ translator handles its usage e.g. in subqueries as well ;)

**> Query.All(typeof(Customer)).Select("new(Name...

Or how am I supposed to do that? And what if I have a type I'd like to project it to (i.e. if I do NOT want to use anonymous types)?**

Yes, nearly. Unfortunately, you can't project it to non-anonymous type with DynamicLINQ - because it doesn't support this (i.e. it isn't dependent on us).

Hmm, it seems I forgot to mention that example relies on DynamicLINQ as well.

> What's the best practice for implementing a Where(...) clause? Using Dynamic LINQ? Or have you developed another option?

Yes, DynamicLINQ is the simplest option. Another is, well, you know - manual expression tree construction.

> ... will the query automatically prefetch the required fields (namely AssignedTo.Name and AssignedTo.Salary from the referenced Employee type)?

Hopefully :) Actually this depends on expression generated by DynamicLINQ. As far as I can judge, it must be identical to the expression in string. Thus DO will prefetch all the fields used there.