Extracting the First (Oldest) Value from Dataset Based on Column Value - sql

Question

I don't have a great deal of experience working with DataSets and haven't been able to find the best way of achieving what I want to achieve.
I basically create a DataSet using a SQL Query and then I am trying to find a Specific Value in the 'Field' column and then if there is a 'Y' in the 'Flag' (as apposed to a 'N') Column on the same Row then I want it to change a check box's state to Checked as well as updating a labels text.
What I have seems to work however if no data is returned I get the below error:
Object reference not set to an instance of an object
If I change the code slightly from .FirstOrDefault() to .First() I get this error:
Sequence contains no elements
The part of the code that appears to be causing the problem is listed below. If you need to know anything else I will add it in.
Dim sSQL As String
sSQL =
<SQL>
SELECT MAX(UpdateTime) AS UpdateTime FROM AdminCS_Data_Current
WHERE UpdateUser = |##UpdateUser|
</SQL>
sSQL = Replace(sSQL, "##UpdateUser", AdminCB.Text)
Me.LastUserUpdate.Text = "Last Action: " & Format(ReturnDatabaseValue(sSQL, "UpdateTime", "Data"), "dd/MM/yyyy HH:mm:ss")
Dim EmployeeDataset As New DataSet
Try
sSQL =
<SQL>
SELECT * FROM AdminCS_Data_Current
WHERE UpdateUser = |##UpdateUser| AND CONVERT(DATE, UpdateTime) = CAST(GETDATE() AS DATE)
ORDER BY UpdateTime ASC
</SQL>
sSQL = Replace(sSQL, "##UpdateUser", AdminCB.Text)
EmployeeDataset = ReturnDataSet(sSQL, "Data")
If EmployeeDataset IsNot Nothing Then
Dim eData = EmployeeDataset.Tables(0)
If (eData.Select("Field = 'Timesheets Checked'").FirstOrDefault()("Flag")) IsNot Nothing Then
If eData.Select("Field = 'Timesheets Checked'").FirstOrDefault()("Flag").ToString.Trim = "Y" Then
TShtY.CheckState = CheckState.Checked
TShtTime.Text = Format(eData.Select("Field = 'Timesheets Checked'").First()("UpdateTime"), "HH:mm:ss")
Else
TShtN.CheckState = CheckState.Checked
End If
End If
' The above two IF statements would be repeated several times on each change of "Field"
End If

Answer 1

It would appear that this code has introduced not just iunefficiency but also a bug:
If (eData.Select("Field = 'Timesheets Checked'").FirstOrDefault()("Flag")) IsNot Nothing Then
If eData.Select("Field = 'Timesheets Checked'").FirstOrDefault()("Flag").ToString.Trim = "Y" Then
TShtY.CheckState = CheckState.Checked
TShtTime.Text = Format(eData.Select("Field = 'Timesheets Checked'").First()("UpdateTime"), "HH:mm:ss")
Else
TShtN.CheckState = CheckState.Checked
End If
End If
It should have been written like this in the first place:
Dim row = eData.Select("Field = 'Timesheets Checked'").FirstOrDefault()
If row IsNot Nothing Then
If row("Flag").ToString.Trim = "Y" Then
TShtY.CheckState = CheckState.Checked
TShtTime.Text = Format(row("UpdateTime"), "HH:mm:ss")
Else
TShtN.CheckState = CheckState.Checked
End If
End If
Easier to read, more efficient and avoids that nasty bug.
Also, I'd much rather see this:
Dim row = eData.Select("Field = 'Timesheets Checked'").FirstOrDefault()
If row IsNot Nothing Then
If row("Flag").ToString.Trim = "Y" Then
TShtY.Checked = True
TShtTime.Text = CDate(row("UpdateTime").ToString("HH:mm:ss")
Else
TShtN.Checked = True
End If
End If
You should never use the CheckState of a Checkbox unless it's tri-state, which maybe yours are but I doubt it. As for Format, we're not in VB6 anymore Toto.