The following search will use the first of four SelectMany
overloads. ()
Example 1
var v = from pa in dataContext.Person
from n in
pa.PersonNames
where
n.FirstName.StartsWith("M")
select n;
I have this working.
Now I need to have a more realistic situation whereby the query will
cross multiple collections. For example
the below code:
Example 2
var v = from pa in dataContext.Person
from n in
pa.PersonNames
from i in
pa.PersonIdentifiers
where n.FirstName.StartsWith("M")
|| i.Ident.Equals("1001")
select n;
With this query in Example 2, I believe I need to use a
different overload of the SelectMany extension method than I used in Example
1. The overload wich I think I need is
the following:
public static IQueryable<TResult>
SelectMany<TSource, TCollection, TResult>(
this
IQueryable<TSource> source,
Expression<Func<TSource, IEnumerable<TCollection>>>
collectionSelector,
Expression<Func<TSource, TCollection, TResult>>
resultSelector
)
My initial attempt was:
ParameterExpression personExp =
Expression.Parameter(typeof(Person), "Person");
var selectManyNameArg =
Expression.Lambda<Func<Person,
IEnumerable<PersonName>>>(
Expression.Property(personExp,
"PersonNames"), personExp);
var selectManyIdenArg =
Expression.Lambda<Func<Person,
IEnumerable<PersonIdentifier>>>(
Expression.Property(personExp,
"PersonIdentifiers"), personExp);
Expression selectManyCall = Expression.Call(
typeof(Queryable),
"SelectMany",
new Type[] {
typeof(Person), typeof(PersonName), typeof(PersonIdentifier)},
Expression.Constant(queryableData),
selectManyNameArg,
selectManyIdenArg);
But again I keep getting the same exception which is being
thrown from the SelectMany extension method. The arguments I have provided do
not match up with any of the signatures for the SelectMany overloads. Documentation on Expression Trees (other
than the simple expression1 greater than expression2 samples) is scarce. At this point I am not even sure what the
best way to debug the issue is. Any help
would be appreciated.
