Query SQL Database and Store Results in a Variable VB.Net - sql

Question

I am trying to query a SQL DB using a textbox field and retreive a column from the DB and store it in a variable so I can use it in other places within my site. My web form requires the user to enter a few items such as name and zip code.
My database has 3 columns; email address, zip code, and id. I need the input form to query the database and return the "email address" that matches the user's inputted "zip code"
I understand the SQL SELECT statement and the connection string is correct. My queries are working, I just can't seem to figure out how to get the returned "email address" to store in a variable. Any help would be appreciated.
Dim strconnection As String, strSQL As String, strZipCheck As String
Dim objconnection As OleDbConnection = Nothing
Dim objcmd As OleDbCommand = Nothing
Dim RREmail As String = Nothing
Dim zipQuery As String = zipCodeBox.Text
'connection string
strconnection = "provider=SQLOLEDB;Data Source=XXX.XXX.XXX.XXX;Initial Catalog=XXXXXXX;User ID=XXXX;Password=XXXXXXXX;"
objconnection = New OleDbConnection(strconnection)
objconnection.ConnectionString = strconnection
'opens connection to database
objconnection.Open()
strSQL = "SELECT [EMAIL ADDRESS] FROM ZIPCODEDATA WHERE [ZIP CODE] = #ZIP CODE "
objcmd = New OleDbCommand(strSQL, objconnection)
RREmail = CType(objcmd.ExecuteScalar(), String)
lblRREmail.Text = RREmail
objconnection.Close()

Answer 1

While the other comments do point out particular deficiencies with your syntax, I would like to address the question of storing a variable and take it a bit further. I generally do not use parameterized connections unless I am calling stored procedures and need an output parameter. Instead, here is what I often do to create a database connection and get my results.
First I create a public class called dbConn so I dont have to write it out a million times.
Imports System.Data.SqlClient
Public Class dbConn
Public Property strSQL As String
Private objConn As SqlClient.SqlConnection = _
New SqlClient.SqlConnection("Data Source=(local)\dev;Initial Catalog=testDataBase;Persist Security Info=False;Integrated Security = true;")
Public Function getDt() As DataTable
Dim Conn As New SqlClient.SqlConnection
Dim da As SqlClient.SqlDataAdapter
Dim dt As New DataTable
Try
objConn.Open()
da = New SqlClient.SqlDataAdapter(strSQL, objConn)
da.Fill(dt)
da = Nothing
objConn.Close()
objConn = Nothing
Catch ex As Exception
objConn.Close()
objConn = Nothing
End Try
Return dt
End Function
End Class
Then from another class (lets assume its form1) I call up that function to get a datatable returned to me. In this case I select TOP 1 to save your sanity in case by chance there is more than one email address per zip code.
Public sub getdata()
Dim strEmailAddress As String = Nothing
Dim dt As New DataTable
Dim da As New dbConn
da.strSQL = " select top 1 [email address] from [zipcode] " _
& " where [zip code] = '" & strZipCode & "'" _
& " order by [email address] asc"
dt = da.getDt
If dt.Rows.Count > 0 Then
If Not IsDBNull(dt.Rows(0)(0).ToString) Then
strEmailAddress = dt.Rows(0)(0).ToString
End If
End If
End Sub
From there you can use strEmailAddress within the sub after it is set, or you can move the string declaration outside of the sub as a public string declaration to use it elsewhere, or you can create other classes like an email class with a public property for strEmailAddress to pass it off to, etc.
I hope something in there helps you understand how to deal with your problem.