Retrieving Stored Procedure Results - sql-server

Question

I'm trying to switch a user between three different screens depending on what a stored procedure returns in a BtnView_Click procedure in asp.net VB. The SP would return a "0, 1, or NULL". Currently it's only returning a "1" and not the others. I'm having trouble with the Reader.Read area with the IF statement and i'm wondering if there's a simple fix to this so it directs everything accuratley.
This is what I currently have (updated)
Sub BtnView_Click(ByVal sender As Object, ByVal e As CommandEventArgs)
Session.Add("SvarRecord", e.CommandArgument)
Dim sb As New System.Text.StringBuilder()
Dim connectionString As String = ConfigurationManager.ConnectionStrings("CS_Connection").ConnectionString
Using connection As New SqlConnection(connectionString)
Dim myCommand As New SqlCommand("View", connection)
myCommand.CommandType = CommandType.StoredProcedure
Dim sqlRecord As SqlParameter = New SqlParameter("#Name", SqlDbType.VarChar)
sqlRecord.Value = Session("SvarRecord")
myCommand.Parameters.Add(sqlRecord)
connection.Open()
Using reader As SqlClient.SqlDataReader = myCommand.ExecuteReader
REM Read() returns True if data can be read
If reader.Read() Then
REM IsDbNull checks if given column (by ordinal) contains DbNull.
REM You need it because you can not convert DbNull to a number. As alternative
REM you may read it as object and compare by yourself.
If reader.IsDBNull(0) Then
Response.Redirect("Entry.Aspx")
REM We are sure it is not DbNull and we can assume it is an integer
ElseIf reader.GetInt32(0) = 0 Then
Response.Redirect("Negatives.Aspx")
ElseIf reader.GetInt32(0) = 1 Then
Response.Redirect("PrevEntry.Aspx")
End If
End If
reader.Close()
End Using
connection.Close()
connection.Dispose()
End Using

Answer 1

You're comparing HasRows property (a Boolean that indicates if recordset is empty or not), not value returned from your stored procedure.
Change your code to:
Using reader As SqlClient.SqlDataReader = myCommand.ExecuteReader
Rem Read() returns True if data can be read
If reader.Read() Then
Rem IsDbNull checks if given column (by ordinal) contains DbNull.
Rem You need it because you can not convert DbNull to a number.
Rem As alternative you may read it as object and compare by yourself.
If reader.IsDbNull(0) Then
Response.Redirect("Entry.Aspx")
Rem We are sure it is not DbNull and we can assume it is an integer
ElseIf reader.GetInt32(0) = 0 Then
Response.Redirect("Negatives.Aspx")
ElseIf reader.GetInt32(0) = 1 Then
Response.Redirect("PrevEntry.Aspx")
End If
End If
End Using
Here I assume your stored procedure returns an integer value. If it's not you can get/compare with right value or convert it to integer. First case (same for the other If):
ElseIf reader.GetString(0) = "0" Then
Second case:
ElseIf Convert.ToInt32(reader.GetObject(0)) = 0 Then
Last note about your code, as suggested by Jhon in his comment your code may fail for an unlimited number of reasons, you'd better to always wrap disposable objects in a Using statement like this:
Dim connectionString As String =
ConfigurationManager.ConnectionStrings("CS_Connection").ConnectionString)
Using connection As New SqlConnection(connectionString)
Rem Put here all code that uses connection
End Using
This will ensure connection and other shared (and limited!) resources will always be released even in case of error. Edit: compiler won't complain about comparison of a Boolean and a String because you didn't set OPTION STRICT to ON (see #Tim's answer for more details).

Answer 2

First, use the Using-statement to dispose/close the connection and anything else implementing IDisposable even on error. Second, you should really set OPTION STRICT to on globally, then this will not compile which is a good thing:
If reader.HasRows = "0" Then
The problem with that code is that HasRows is a Boolean but you are comparing it with a String. That would result in a compiler error normaly, but OPTION STRICT off allows it. The Boolean will be converted to a String implicitely. So this comparison seems to work but it does not.
Actually you have to read the field, you can use the Get... methods:
If reader.HasRows Then
If reader.IsDBNull(0) Then
Response.Redirect("Entry.Aspx")
ElseIf reader.GetInt32(0) = 1 Then
Response.Redirect("PrevEntry.Aspx")
ElseIf reader.GetInt32(0) = 0 Then
Response.Redirect("Negatives.Aspx")
End If
End If