LINQ expression to expression tree via API in VB - vb.net

Question

I have a relatively simple LINQ expression which I need to convert into VB expression tree syntax. This is likely an easy task for folks that are familiar, but I am new to the realm of LINQ expression trees.
In my samples, you see a "New Int16() {}" array. That value must be parameterized at run-time with an array of values from another code element.
my query is:
from i in tblInstitutions
let ChildHasCategory = i.tblInstCtgyHistories.Where(Function(CtgyHist) CtgyHist.EndDate is Nothing AND ( (New Int16() {32,35,38,34}).Contains(CtgyHist.InstCtgyCodeFK)))
where ChildHasCategory.Any()
select i
Which can also be represented as:
tblInstitutions
.Select (i => new {
i = i,
ChildHasCategory = (IEnumerable<tblInstCtgyHistory>)(i.tblInstCtgyHistories)
.Where (
CtgyHist =>
((CtgyHist.EndDate == null) &
(IEnumerable<Int16>)(new Int16[] { 32, 35, 38, 34 } ).Contains (CtgyHist.InstCtgyCodeFK)
)
)
}
)
.Where ($VB$It => $VB$It.ChildHasCategory.Any ())
.Select ($VB$It => $VB$It.i)
This is going to be used in the context of a custom filter in an ASP.NET Dynamic Data web application. I'd like to mimic the default approach.
A sample of one of the other dynamic filter code-behind is:
Public Overrides Function GetQueryable(source As IQueryable) As IQueryable
Dim value = TextBox1.Text
If String.IsNullOrWhiteSpace(value) Then
Return source
End If
If DefaultValues IsNot Nothing Then
DefaultValues(Column.Name) = value
End If
Dim parameter = Expression.Parameter(source.ElementType)
Dim columnProperty = Expression.PropertyOrField(parameter, Column.Name)
Dim likeValue = Expression.Constant(value, GetType(String))
Dim condition = Expression.Call(columnProperty, GetType(String).GetMethod("Contains"), likeValue)
Dim where = Expression.Call(GetType(Queryable), "Where", New Type() {source.ElementType}, source.Expression, Expression.Lambda(condition, parameter))
Return source.Provider.CreateQuery(where)
End Function

Answer 1

I'm not sure you really need to worry about expression trees here. First off, we should be able to express your query as follows:
Dim targetCodes = new Int16() {32, 35, 38, 34 } ' This could be data driven as well
return from i in tblInstitutions
where i.tblInstCtgyHistories.Any(Function(ctgyHist) ctgyHist.EndDate is Nothing AndAlso
targetCodes.Contains(ctgyHist.InstCtgyCodeFK))
select i
Given that, under what case do you need the custom expression tree?