CODEWITHSUNDEEP
vb.netms-access
dotnetdevcsharp
dotnetdevcsharp

Reputation: 3980

Error when using linq on datatable

I am trying to run the following code converting my datatable to be usable in linq all seems fines and compiles but when I Execute the statement I get the following statement i get the error below new entires just has location and ordernumber in the return values I have to do it this way as I am supporting a legacy access 97 system thanks.

 Dim total = From row In newEntries.AsEnumerable()
            Select row.Field(Of Int32)("location") Distinct
    retVal = Convert.ToInt32(total)

enter image description here

This is my whole code but im still getting an invalid type cast error their is data exsits for this order by teh way 

        Dim retVal As Int32
       Dim newEntries As New DataTable
     Dim script As String = scriptBuilder.GetDistinctOrdersForLocations(OrderNumber)
    newEntries = connection.SqlSelectToDataTable(script)
    Dim total = From row In newEntries.AsEnumerable()
            Select row.Field(Of Int32)("location") Distinct
    retVal = total.Count()

Upvotes: 0

Views: 193

Answers (4)

Ric
Ric

Reputation: 13248

If you want the count of the collection just do this:

retVal = total.Count()

this will return the count from the distinct query that you have written.

Just to clarify, @David B identified the data type of location was int16 not int32, so changing this in the linq query resolved the issue.

Upvotes: 3

dotnetdevcsharp
dotnetdevcsharp

Reputation: 3980

I changed the code to int16 worked here is the code for any one else stuck thanks @Ric 

    Dim retVal As Int32
    Dim newEntries As New DataTable
     Dim script As String = scriptBuilder.GetDistinctOrdersForLocations(OrderNumber)
    newEntries = connection.SqlSelectToDataTable(script)
    Dim total = From row In newEntries.AsEnumerable()
            Select row.Field(Of Int16)("location") Distinct
    retVal = total.Count()

Upvotes: 0

BlueMonkMN
BlueMonkMN

Reputation: 25601

It's important to understand when you write a LINQ query and assign it to a variable, that variable essentially contains a query object, and not the results of running the query. In order to get the value that results from the query, you need to call some method on the query object such as:

total.Single() ' Assumes you expect the query to return exactly one result.

Upvotes: 0

jwatts1980
jwatts1980

Reputation: 7356

Your LINQ query is returning a collection. You should use something like First or FirstOrDefault.

I'm a little rusty on VB LINQ, but try :

retVal = Convert.ToInt32(total.First())

Note: This will throw an error if there are no items in the collection.

Upvotes: 0

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