Binary expresion CompareTo can't be converted to a predicate expression
Joined: 05-Mar-2008
Joined: 05-Mar-2008
Ok, this is what you should do: - create a class similar like the one I created below. - when LinqMetaData is instantiated, pass an instance of the functionmappings to the linqmetadata constructor like I did in the example below.
that's it.
Example function mapping class (tested it on adventureworks, of course you should name it differently 
)
internal class AdventureWorksFunctionMappings : FunctionMappingStore
{
public AdventureWorksFunctionMappings()
: base()
{
this.Add(new FunctionMapping(typeof(Guid), "CompareTo", 1, "CASE WHEN {0} < {1} THEN -1 WHEN {0} = {1} THEN 0 ELSE 1 END"));
}
}
example usage:
[Test]
public void CompareToOnGuidTest()
{
using(DataAccessAdapter adapter = new DataAccessAdapter())
{
LinqMetaData metaData = new LinqMetaData(adapter, new AdventureWorksFunctionMappings());
var q = (from a in metaData.Address select a)
.Where(a => a.Rowguid.CompareTo(new Guid("57f73b00-26b1-11df-8600-001c2311de1b")) < 0);
int count = 0;
foreach(var v in q)
{
count++;
}
Assert.AreEqual(6, count);
}
}
So where you instantiate the LinqMetaData object you've to specify the instance of your custom function mapping class.
We didn't add a CompareTo() mapping for every type to every DQE as in general it's not necessary to do so. With Guid's it's indeed a different matter, as Guid doesn't implement the '<' or '>' operator. I'm not sure if the query above gives the results you want btw, as comparing Guids is not that easy (as endy-ness has to be taken into account)
Joined: 05-Mar-2008
Joined: 05-Mar-2008
Could you give me the stacktrace where the exception occurs? The WithPath is just another method call at the client so the error happens on the server. To make it easier to find where exactly the exception occurs, it's best if you post the stacktrace so we can look at that method 
Joined: 05-Mar-2008
yes, I see why it goes wrong there. The IQueryable withpath works on, is our provider (LinqMetaData), and it contains the ElementCreator object, which is necessary to create objects from classes in the generated code without the dependency on those classes in the linq provider.
the only way to solve this IMHO is to replace the elements of interlinq in the expression tree at the service with an LLBLGenProQuery instance, using the LinqMetaData instance of the service. This is somewhere in the object returned by the Get<> method IMHO as it would otherwise also never work without WithPath.
I have no knowledge about how interlinq works, though our linq provider has visitor classes which can easily transform whatever node into another one so it's easy to write a visitor class which processes the expression tree on the service, replaces the interlinq objects with objects as if the expression tree was created locally and then you can execute it. However, it requires interlinq's help, as I can't write that class for you as I don't know how interlinq works.
If you want to know how these visitor classes look like, please look into the LinqSupportClasses sourcecode, the ExpressionHandlers namespace/folder and for example at the ExpressionReplacer handler, which is a visitor which can traverse an entire expression tree and replace expressions it understands with expressions it finds in the set it contains.
But again, I have no idea what this 'Get' method does and where inside the data-structure it returns the original expression tree it represents is located.
I thought about a workaround for you, but they all come down to appending WithPath methods, which of course won't work with this linq tree at the service. 