Connecting To A Database Via Class Object Visual Basic 2010 - mysql

Question

i have 2 classes
connect class
Imports MySql.Data
Imports MySql.Data.MySqlClient
Public Class connect
Dim dbCon As MySqlConnection
Dim strQuery As String = ""
Dim SqlCmd As MySqlCommand
Dim DR As MySqlDataReader
Public Function Con2Db() As Boolean
Try
'Prepare connection and query
dbCon = New MySqlConnection("Server=localhost; User Id = root; Pwd = 12345; Database = digitallibrary")
If dbCon.State = ConnectionState.Closed Then
dbCon.Open()
Return True
Else
dbCon.Close()
splash.Label1.Text = "Connection is Close"
Return False
End If
Catch ex As Exception
MsgBox("FAIL")
Return False
End Try
End Function
End Class
And query Class
Imports MySql.Data
Imports MySql.Data.MySqlClient
Public Class query
Dim dbCon As MySqlConnection
Dim strQuery As String = ""
Dim SqlCmd As MySqlCommand
Dim DR As MySqlDataReader
Public Sub insert(ByVal ln As String, ByVal fn As String, ByVal mn As String, ByVal user As String, ByVal email As String, ByVal bdate As String, ByVal jdate As String, ByVal jtime As String, ByVal pwd As String)
Try
strQuery = "INSERT INTO user_tbl(user_ln,user_fn,user_mn,username,user_email,user_bdate, user_jdate, user_jtime)VALUES('" + ln + "','" + fn + "','" + mn + "','" + user + "','" + email + "','" + bdate + "','" + jdate + "','" + jtime + "' );" & _
"INSERT INTO login_tbl(username,password)VALUES('" + user + "','" + pwd + "')"
SqlCmd = New MySqlCommand(strQuery, dbCon)
SqlCmd.ExecuteNonQuery()
dbCon.Close()
Catch ex As Exception
MsgBox("Error " & ex.Message)
End Try
End Sub
End Class
Also A registration form
Public Class registration
Private Sub registration_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim con As New connect
If (con.Con2Db = True) Then
Label13.Text = "Connected To Database"
Else
Label13.Text = "Not Connected To Database"
End If
End Sub
Private Sub submit_btn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles submit_btn.Click
Dim ins As New query
Dim ln As String = ln_txt.Text
Dim fn As String = fn_txt.Text
Dim mn As String = mn_txt.Text
Dim user As String = user_txt.Text
Dim pwd As String = pwd_txt.Text
Dim cpwd As String = cpwd_txt.Text
Dim email As String = email_txt.Text
Dim year As String = year_cbx.Text
Dim month As String = month_cbx.Text
Dim day As String = day_cbx.Text
Dim bdate As String = year + "-" + month + "-" + day
Dim jdate As String = Format(Date.Now, "yyyy-MM-dd")
Dim jtime As String = Format(Date.Now, "HH:mm:ss")
ins.insert(ln, fn, mn, user, email, bdate, jdate, jtime, pwd)
End Sub
End Class
Everything is okay and it is saying on the label that the connection is successful but when I run the code it gives an error
Error Connection must be valid and open
I don't understand why the connection is said to be closed when the function is returning true...
If people are wondering why separate it to each classes it's because i'm trying to code cleanly(i hope and think) and i want to be more flexible in programming

Answer 1

The problem is that your 'connect' class has no relationship to your 'insert' function, meaning you are creating a new connection in each one. What you would have to do is create a Shared connection to your database that your connect class would manage, and your 'insert' function would use the existing connection.
There is nothing wrong with separating code into various sections, but you must know how to do it efficiently. I typically keep connection management and query execution in the same sections to avoid passing around extra objects. Here is what I would do:
Imports MySql.Data
Imports MySql.Data.MySqlClient
Public Class QueryManager
Dim dbCon As MySqlConnection
Public Sub ManageConnection(ByVal CloseConnection As Boolean)
Try
'Prepare connection and query'
dbCon = New MySqlConnection("Server=localhost; User Id = root; Pwd = 12345; Database = digitallibrary")
If CloseConnection = False Then
If dbCon.State = ConnectionState.Closed Then _
dbCon.Open()
Else
dbCon.Close()
End If
Catch ex As Exception
MsgBox("FAIL")
End Try
End Sub
Public Sub Insert(ByVal ln As String, ByVal fn As String, ByVal mn As String, ByVal user As String, ByVal email As String, ByVal bdate As String, ByVal jdate As String, ByVal jtime As String, ByVal pwd As String)
Try
ManageConnection(True) 'Open connection'
Dim strQuery As String = "INSERT INTO user_tbl(user_ln,user_fn,user_mn,username,user_email,user_bdate, user_jdate, user_jtime)" & _
"VALUES('" + ln + "','" + fn + "','" + mn + "','" + user + "','" + email + "','" + bdate + "','" + jdate + "','" + jtime + "' );" & _
"INSERT INTO login_tbl(username,password)VALUES('" + user + "','" + pwd + "')"
Dim SqlCmd As New MySqlCommand(strQuery, dbCon)
SqlCmd.ExecuteNonQuery()
ManageConnection(False) 'Close connection'
Catch ex As Exception
MsgBox("Error " & ex.Message)
End Try
End Sub
End Class
You would also no longer require the 'registration_Load' sub since the connection will only be opened while it's being used. If you wanted to create one shared connection and persist it through the entire application, you could adjust the functions to reflect your needs.