Question

I’ve got the following code:

Dim query As IQueryable(Of someObject) = 
    New ObjectQuery(Of someObject)(queryString, db, MergeOption.NoTracking)
        .Where(CType(Function(x) x.Publish = True,
                     Expression(Of Func(Of someObject, Boolean))))

And it gives me an error that says:

Cannot convert expression of type Func(someObject) System.Nullable(Of
Boolean) to type System.Linq.Expressions.Expression(Of
System.Func(someObject, Boolean)).

I have also tried:

 .Where(CType(Function(x) x.Publish = True,
                     Expression(Of Func(Of someObject, Nullable(Of Boolean)))))

which doesn’t work either.

If I don’t have the CType my where comes up with a narrowing conversion error from IQueryable and IEnumerable, so I need that there, but I am not sure how to write that where parameter as an expression to so it can be converted. Any help?

Answer 1

Don’t use casting with CType here – create the expression directly:

Dim expr As Expression(Of Func(Of someObject, Nullable(Of Boolean))) =
    Function(x) x.Publish = True

Dim query As IQueryable(Of someObject) = 
    New ObjectQuery(Of someObject)(queryString, db, MergeOption.NoTracking)
        .Where(expr)

Expressions need to be created as such. It’s not possible to convert existing Func into an expression.