title: OLEDBException: No value given for one or more required parameters in vb.net
body: <p>I'm new to programming and am having a problem with a web application I am coding in VB.net. I have an Access database in my project and am using a parameterized query to retrieve information from it. The weird thing is, I use almost the same query on another page that works fine, but this one gives me teh "No value given for one or more required parameters" error. I have been searching most of the day and realize the question has been asked but can't find the solution to my problem. I think I am using the "?" correctly, have the right number of parameters in the right order, and everything is spelled right. Here is my code:</p>
  
  <pre><code> Dim strWthStn As String
      strWthStn = cboRainProb2.Text
      Dim strWthStnParm As New OleDb.OleDbParameter()
      strWthStnParm.Value = strWthStn
  
      Dim strMonth As String
      strMonth = cboRainProb.Text
      Dim strMonthParm As New OleDb.OleDbParameter()
      strMonthParm.Value = strMonth
  
      Dim sql As String 'Query to select the station for rainfall probability values
  
      sql = "SELECT 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 " &amp;
      "FROM Rainfall Probability " &amp;
      "WHERE Station = ?" &amp;
      "AND Mth = ?"
  
      'Connects to the Access database and selects data based on query
      Dim AccessConnect As String
      AccessConnect = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=F:\Megan\Visual Studio Projects\DroughtCalculatorND_Web\DroughtCalculatorND_Web\NDStations.mdb"
      Dim conn As New OleDb.OleDbConnection
      Dim selectCommand As New OleDbCommand(sql, conn)
      selectCommand.Parameters.Add(strWthStnParm)
      selectCommand.Parameters.Add(strMonthParm)
      conn.ConnectionString = AccessConnect
      conn.Open()
  
      'Reads the data into a list
      Dim reader As OleDbDataReader =
          selectCommand.ExecuteReader(CommandBehavior.CloseConnection)
      Dim RainByYear As New List(Of Double)
      reader.Read()
      RainByYear.Add(reader("1999"))
      RainByYear.Add(reader("2000"))
      RainByYear.Add(reader("2001"))
      RainByYear.Add(reader("2002"))
      RainByYear.Add(reader("2003"))
      RainByYear.Add(reader("2004"))
      RainByYear.Add(reader("2005"))
      RainByYear.Add(reader("2006"))
      RainByYear.Add(reader("2007"))
      RainByYear.Add(reader("2008"))
      RainByYear.Add(reader("2009"))
      RainByYear.Add(reader("2010"))
  
      RainByYear.Sort()
  </code></pre>
  
  <p>etc.</p>
  
  <p>The program errors at the Dim reader at OleDBDataReader line. I used a breakpoint there to check everything and both parameters had the correct value. I appreciate any help, thanks.</p>