VB.NET: LINQ Query on DataTable - WHERE Id >=0 - database

Question

Hey people,
I am bugfixing an application for some friends of mine. They are using VB.NET and Windows Forms, while I am in team C#/WPF/ASP. My knowledge about LINQ is also very limited even if its all .NET. I hope you can help me.
The situation
There are two combos on the form.
They are getting their data from the same table status.
The order of the status objects depends on the id-column.
The second combo shall only contain status having id >= combo1.id. So that the user can only select status in the second combo that are "greater-equal" than the status in the first combo.
The smallest status.id is 3.
The code
(please ignore the useless back and forward casting of index etc. I wanted to show you the code as I revieved it.)
Dim index As String = cmbStatusFrom.SelectedValue.ToString()
If index = "0" Then
index = "1"
End If
Dim query As IEnumerable(Of DataRow) = _
From status In ContextDataTable.AsEnumerable() _
Where status.Field(Of Integer)("Id") >= Integer.Parse(index) _
Select status
The problem
Without
If index = "0" Then
index = "1"
End If
the resulting datatable contains one more row than it should.
(0 means that the empty-item has been selected in the first combo) The row has id = 0 (like the empty-row)
Again, the smallest existing id is 3. So it should not make any difference if one uses >=0, 1, 2 or 3. But it seemingly does. Or more likely, there is some really stupid mistake in the code and which I just can't find.
Anyone has got an idea what the problem is?
I do appreciate any help. :-)
greetz steven

Answer 1

I'd like to help, but I'm not quite sure I understand your question. Given the information you have here, that code should work. The only unknown is the actual datatype of the value of the combo, but unless the .Field(Of T) is throwing an InvalidCastException, you should be good there. I wrote the following code and threw it into a unit test project, and everything came out good . . . at least with regard to the length of the resulting set of data.
Code
<TestCase(0, ExpectedResult:=4)>
<TestCase(1, ExpectedResult:=4)>
<TestCase(2, ExpectedResult:=3)>
<TestCase(3, ExpectedResult:=2)>
<TestCase(4, ExpectedResult:=1)>
<TestCase(5, ExpectedResult:=0)>
Public Function tmptest(ByVal selected As Integer) As Integer
Dim d As New DataTable
d.Columns.Add(New DataColumn("id", GetType(Integer)))
For j = 0 To 5
Dim r = d.NewRow()
r("id") = j
d.Rows.Add(r)
Next
If selected = 0 Then selected = 1
Dim query = From status In d.AsEnumerable()
Where status.Field(Of Integer)("id") > selected
Select status
Return query.Count
End Function
Results