I have the below code return an AsQueryable object from the controller. The Search function works with no errors, and the object returned is AsQueryable(). 

Public Function Search(ssViewModel As VehicleTheftRecoveryVM) As ActionResult
Dim siteSearchResults As IQueryable(Of VehicleTheftRecoveryVM)
Dim siteSearchViewModel As New VehicleTheftRecoveryVM()
If ssViewModel IsNot Nothing Then
siteSearchViewModel = ssViewModel
End If
TryUpdateModel(siteSearchViewModel)
Try
Dim siteSearchCriteria As VehicleTheftRecoveryVM = SetSearchCriteria(siteSearchViewModel)
siteSearchResults = FilterSearchResultsForSearchCriteria(SessionMgr.User.Id, siteSearchCriteria)

Catch ex As Exception
Debug.WriteLine(ex.Message)
End Try

Return View(siteSearchResults)
End Function

Public Function FilterSearchResultsForSearchCriteria(userId As Integer, searchCriteria As VehicleTheftRecoveryVM) As IQueryable(Of VehicleTheftRecoveryVM)
Dim siteQuery = NoFilterSearchResults(userId)
Try
If (Not IsNothing(searchCriteria)) Then

If searchCriteria.StartDate <> Date.MinValue Then
siteQuery = siteQuery.Where(Function(site) site.StartDate >= searchCriteria.CreateDate)
End If

If searchCriteria.StartDate <> Date.MinValue Then
Dim endDate = searchCriteria.StartDate.AddDays(1)
siteQuery = siteQuery.Where(Function(site) site.StartDate <= endDate)
End If

If Not String.IsNullOrEmpty(searchCriteria.StatusIdString) Then
siteQuery = siteQuery.Where(Function(site) site.StatusIdString IsNot Nothing AndAlso site.StatusIdString = searchCriteria.StatusIdString)
End If

If Not String.IsNullOrEmpty(searchCriteria.CountyLookupIdString) Then
siteQuery = siteQuery.Where(Function(site) site.CountyLookupIdString IsNot Nothing AndAlso site.CountyLookupIdString = searchCriteria.CountyLookupIdString)
End If

End If

Catch ex As Exception
Debug.WriteLine(ex.Message)
End Try

Return siteQuery.AsQueryable()
End Function

However, I'm getting the following error when I the isGrid binds.

infragistics.ui.grid.framework.js:30 Uncaught Error: The remote request to fetch data has failed: ( 500 Internal Server Error )
at $.<computed>.<computed>._renderData (infragistics.ui.grid.framework.js:30)
at $.<computed>.<computed>._renderData (VM767 jquery-ui-1.10.4.js:401)
at proxy (jquery-2.1.1.js:513)
at Class._errorCallback (infragistics.datasource.js:36)
at fire (jquery-2.1.1.js:3073)
at Object.fireWith [as rejectWith] (jquery-2.1.1.js:3185)
at done (jquery-2.1.1.js:8253)
at XMLHttpRequest.<anonymous> (jquery-2.1.1.js:8598)

Below is the grid.

function bindSitesGrid() {
try {
$("#TheftGrid").igGrid({
responseDataKey: 'Records',
width: "100%",
height: "400",
autoGenerateColumns: false,
primaryKey: "VTRID",
fixedHeaders: true,
requestType: "Post",
columns: [
{ key: "VTRID", headerText: "", hidden: true },
{
key: "MRN",
headerText: "MRN",
dataType: "string",
width: "10%"
},
{
key: "AgencyTrackingNumber",
headerText: "Agency Tracking Number",
dataType: "string",
width: "10%"
},
{
key: "StartDate",
headerText: "Create Date",
dataType: "date",
width: "10%"
},
{
key: "Agency",
headerText: "Agency",
dataType: "string",
width: "15s%"
},
{
key: "StatusId",
headerText: "Status",
dataType: "string",
width: "15s%"
},
{
key: "County",
headerText: "County",
dataType: "string",
width: "15%"
},
{
key: "Latitude",
headerText: "Latitude",
dataType: "string",
width: "10%"
},
{
key: "Longitude",
headerText: "Longitude",
dataType: "string",
width: "10%"
},
{
key: "ReportLink",
headerText: "Report Link",
formatter: formatViewSiteDocumentButton,
width: "10%"
}
],
autoGenerateLayouts: false,
features: [
{
name: 'Sorting',
type: 'remote',
sortUrlKey: 'sort',
sortUrlKeyAscValue: 'asc',
sortUrlKeyDescValue: 'desc',
columnSettings: [
{ columnKey: 'MRN', allowSorting: false }
]
},
{ name: 'MultiColumnHeaders' },
{
recordCountKey: 'TotalRecordsCount',
pageIndexUrlKey: 'page',
pageSizeUrlKey: 'pageSize',
name: 'Paging',
type: 'remote',
pageSize: portalUI.pageSize(),
pageSizeDropDownLocation: 'inpager'
}
]
});

var parameters = $('#VTRModifiedCriteriaForm').serialize();
var url = '/VTR/VehicleTheftRecovery/Search/?ticks=' + new Date() + "&" + parameters;

$('#TheftGrid').igGrid('option', 'dataSource', url);
}
catch (error) {
console.log(error)
}

}

And here are properties of the object bound into the AsQueryable object

searchResults = (From site In DataContext.VtrVehicleTheftRecoveries
Group Join countyDistrict In DataContext.CountyDistricts On countyDistrict.CountyLookupId Equals site.CountyLookupId Into countyDistrictGroup = Group From countyDistricts In countyDistrictGroup.DefaultIfEmpty()
Group Join countyLookup In DataContext.Lookups On countyDistricts.CountyLookupId Equals countyLookup.Id Into countyLookupGroup = Group From counties In countyLookupGroup.DefaultIfEmpty()
Select New VehicleTheftRecoveryVM With {
.VTRID = site.Vtrid,
.MRN = site.MasterRecordNumber,
.AgencyTrackingNumber = site.AgencyTrackingNumber,
.StartDate = site.CreatedDate,
.Agency = site.AgencyIdNmb,
.StatusId = site.VtrStatus,
.County = counties.Name,
.Latitude = site.Latitude,
.Longitude = site.Longitude,
.ReportLink = site.LinkMrn
}).OrderByDescending(Function(site) site.MRN)

Return searchResults.ToList()

The only errors I'm getting is the http 500 error shown at the top. Is there anyway to get more detailed error messaging?