Adding Nodes to Tree via LINQ creates "query operator not supported" during runtime

Question

I am trying to get my head around a LINQ issue. The ultimate goal is to load tree view with data acquired from LINQ to SQL (view). The issue is when I try to access the data acquired it keeps throwing a "query operator not supported during runtime". The code involved is no more than:

    Dim tasklistdata As New lqDataContext
    Dim UserID As Integer

    UserID = (From vwUser In tasklistdata.Operators _
             Where vwUser.UserName Is Login.txtUsername.Text _
             Select vwUser.OperatorID).Single

    Dim lqHospitalList = From vwHospitalList In tasklistdata.SPM_Accounts _
                          Where vwHospitalList.OperatorID = UserID _
                          Order By vwHospitalList.CustomerName, vwHospitalList.Class _
                          Select vwHospitalList.CustomerName, vwHospitalList.Class, vwHospitalList.ClassCount, vwHospitalList.Charges

    tvHospitalSelect.Nodes.Add(lqHospitalList(0).CustomerName)

if I were to change the code to lqHospitalList.First.CustomerName it works as expected, however changing it to array position is where the issue arises. Please direct me to where my flaw in logic is.

Answer 1

Linq querys are not lists, so they don't have an index. To iterate over all the items you can use a foreach like so:

For Each hospital In lqHospitalList
    tvHospitalSelect.Nodes.Add(hospital.CustomerName)
Next

If you want to convert the query to a list:

lqHospitalList.ToList

or array:

lqHospitalList.ToArray