How can I compare a text box entry against a list of database values in the Text_Changed event - asp.net

Question

as the title states I am trying to compare or validate a text box entry against a list of acceptable values stored in my database. As of now I have taken the values from my database and store them in a List(of String) and I have a for loop that loops through that list and returns true if the values match, if the values do not match it will return false. Below I have attached the code I am currently working with.
Protected Sub txtSearchOC_TextChanged(sender As Object, e As EventArgs) Handles txtSearchOC.TextChanged
Dim listEType As List(Of String) = New List(Of String)
Dim eType As String = txtSearchOC.Text
Dim strResult As String = ""
lblPrefix.Text = ""
lblList.Text = ""
Dim TypeIDQuery As String = "
SELECT a.OrderCode
FROM SKU AS a
INNER JOIN EnrollmentType AS e ON a.EnrollmentTypeID = e.TypeID
INNER JOIN Enrollment AS f ON e.RecID = f.EnrollmentTypeID
WHERE f.AccountNumber = '12345';
"
Using connEType As New SqlConnection(ConfigurationManager.ConnectionStrings("WarrantyConnectionString").ToString)
Using cmdEType As New SqlCommand(TypeIDQuery, connEType)
cmdEType.Parameters.Add("#AccountNumber", SqlDbType.VarChar, 15).Value = "12345"
connEType.Open()
Using sdrEType As SqlDataReader = cmdEType.ExecuteReader
While sdrEType.Read
listEType.Add(sdrEType("OrderCode").ToString)
End While
End Using
End Using
End Using
For Each Item As String In listEType
strResult &= Item & ", "
Next
For i = 0 To listEType.Count - 1
If eType = listEType(i) Then
lblPrefix.Text = "True"
End If
If eType <> listEType(i) Then
lblList.Text = "Error"
End If
Next
'lblList.Text = strResult
End Sub
In the code I declare my list and a variable to store the text value of the text box. To verify that it pulled the appropriate values from the database I have the strResult variable and can confirm that the appropriate values are being stored.
The problem I am having has to do with the For loop I have at the bottom, when I enter in a valid value that is contained in the listEType, I get the confirmation message of "True" indicating it has matched with one of the values, but I also get the "Error" message indicating that it does not match. If I enter in a value that is not contained in the list I only get the "Error" message which is supposed to happen.
My question is, based on the code I have supplied, why would that For loop be returning both "True" and "Error" at the same time for a valid entry? Also, if there is a better way to accomplish what I am trying to do, I am all ears so to speak as I am relatively new to programming.

Answer 1

Well, as others suggested, a drop down (combo box) would be better.
However, lets assume for some reason you don't want a combo box.
I would not loop the data. You have this amazing database engine, and it can do all the work - and no need to loop the data for such a operation. Why not query the database, and check for the value?
Say like this:
Protected Sub txtSearchOC_TextChanged(sender As Object, e As EventArgs) Handles txtSearchOC.TextChanged
If txtSearchOC.Text <> "" Then
Dim TypeIDQuery As String = "
SELECT a.OrderCode FROM SKU AS a
INNER JOIN EnrollmentType AS e ON a.EnrollmentTypeID = e.TypeID
INNER JOIN Enrollment AS f ON e.RecID = f.EnrollmentTypeID
WHERE f.AccountNumber = #AccoutNumber;"
Using connEType As New SqlConnection(ConfigurationManager.ConnectionStrings("WarrantyConnectionString").ToString)
Using cmdEType As New SqlCommand(TypeIDQuery, connEType)
cmdEType.Parameters.Add("#AccountNumber", SqlDbType.NVarChar).Value = txtSearchOC.Text
connEType.Open()
Dim rstData As New DataTable
rstData.Load(cmdEType.ExecuteReader)
If rstData.Rows.Count > 0 Then
' we have a valid match
lblPrefix.Text = "True"
Else
' we do not have a valid match
lblPrefix.Text = "False"
End If
End Using
End Using
End If
End Sub
So, pull the data into a data table. You can then check the row count, or even pull other values out of that one row. But, I don't see any need for some loop here.