I am trying to make a very simple program that connects to a MySQL database using VB.NET. My program only has one form and one label. I setup my MySQL database to have a table and one field (a VARCHAR)
called "Tab1". I manually inserted the value "CLOSED" into the Tab1 field using PHPMyAdmin. I want my program to change the value of the field to OPEN/CLOSED and I also want the label text on my form to
change too when it's clicked.
So far, I've added the MySQL.data reference to my project and added:
Imports System
Imports System.Data
Imports MySql.Data.MySqlClient
To the General_Declarations
Also I declared a global variable containing a MySQL Connection:
Public Class Form1
Dim conn As New MySqlConnection
Here is my function that connects to MySQL:
Private Function Connect(ByVal server As String, ByRef user As String, ByRef password As String, ByRef database As String)
' Connection string with MySQL Info
conn.ConnectionString = "server=" + server + ";" _
& "user id=" + user + ";" _
& "password=" + password + ";" _
& "database=" + database + ";"
Try
conn.Open()
Return True
Catch ex As MySqlException
Return MsgBox(ex.Message)
End Try
End Function
I made the program connect to MySQL on Form_Load like this:
Connect("db4free.net", "boomun", "*******", "boomdb")
And it connects fine but here is where I have the trouble.... I want the field to change from CLOSED to OPEN when I click Label1. It does, but it doesn't change back on the second click. Somehow I need a working code to Update the Tab1 field in my table.
Here is what I have so far:
Private Sub Label1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Label1.Click
Dim myCommand As New MySqlCommand
Dim myAdapter As New MySqlDataAdapter
Dim myData As MySqlDataReader
Dim SQL As String
SQL = "SELECT * FROM `boomtable` WHERE `Tab1` = 'CLOSED'"
myCommand.Connection = conn
myCommand.CommandText = SQL
myAdapter.SelectCommand = myCommand
Try
myData = myCommand.ExecuteReader()
myData.Read()
If myData.HasRows = 0 Then
' *** UPDATE boomtable SET Tab1 = CLOSED WHERE Tab1 = OPEN ***
Label1.Text = "CLOSED"
myData.Close()
Else
Label1.Text = "OPEN"
' *** UPDATE boomtable SET Tab1 = OPEN WHERE Tab1 = CLOSED ***
myData.Close()
End If
Catch ex As MySqlException
MsgBox(ex.Message)
End Try
End Sub
That UPDATE line isn't working for me... Can anyone please provide a working code? Thanks I really appreciate it!!
Here is the entire code of the project all together:
Imports System
Imports System.Data
Imports MySql.Data.MySqlClient
Public Class Form1
Dim conn As New MySqlConnection
Private Function Connect(ByVal server As String, ByRef user As String, ByRef password As String, ByRef database As String)
' Connection string with MySQL Info
conn.ConnectionString = "server=" + server + ";" _
& "user id=" + user + ";" _
& "password=" + password + ";" _
& "database=" + database + ";"
Try
conn.Open()
Return True
Catch ex As MySqlException
Return MsgBox(ex.Message)
End Try
End Function
Private Sub Label1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Label1.Click
Dim myCommand As New MySqlCommand
Dim myAdapter As New MySqlDataAdapter
Dim myData As MySqlDataReader
Dim SQL As String
SQL = "SELECT * FROM `boomtable` WHERE `Tab1` = 'CLOSED'"
myCommand.Connection = conn
myCommand.CommandText = SQL
myAdapter.SelectCommand = myCommand
Try
myData = myCommand.ExecuteReader()
myData.Read()
If myData.HasRows = 0 Then
' *** UPDATE boomtable SET Tab1 = CLOSED WHERE Tab1 = OPEN ***
Label1.Text = "CLOSED"
myData.Close()
Else
Label1.Text = "OPEN"
' *** UPDATE boomtable SET Tab1 = OPEN WHERE Tab1 = CLOSED ***
myData.Close()
End If
Catch ex As MySqlException
MsgBox(ex.Message)
End Try
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Connect("db4free.net", "boomun", "boom123", "boomdb")
End Sub
End Class
Try the following statement instead:
UPDATE boomtable SET Tab1 = 'OPEN' WHERE Tab1 = 'CLOSED'
Ofcourse use a ExecuteNonQuery method to execute the statement. If you meant that OPEN and CLOSE are variables, use Parameters for that instead (it's safer).
Like this...
Else
Label1.Text = "OPEN"
SQL = "UPDATE boomtable SET Tab1 = 'OPEN' WHERE Tab1 = 'CLOSED'"
myCommand.CommandText = SQL
myCommand.ExecuteNonQuery()
myData.Close()
End If
???
One mistake here is using a global connection object. .Net database connections use a feature called connection pooling, which means most of the time it's really better to create a new connection object for each call out to your database. What you can do is use that global to keep your connection string .
Private Sub Label1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Label1.Click
Dim SQL As String = "SELECT * FROM `boomtable` WHERE `Tab1` = 'CLOSED'"
Using rdrCn As New MySqlConnection(connectionString), _
rdrCmd As New MySqlCommand(SQL, rdrCn)
rdrCn.Open()
Using myData As MySqlDataReader = rdrCmd.ExecuteReader()
SQL = "UPDATE boomtable SET Tab1= @NewState WHERE Tab1 = @OldState"
Using updCn As New MySqlConnection(connectionString), _
updCmd As New MySqlCommand(SQL, updcn)
updCmd.Parameters.Add("@NewState", MySqlDbType.VarChar, 6)
updCmd.Parameters.Add("@OldState", MySqlDbType.VarChar, 6)
If myData.Read()
Label1.Text = "CLOSED"
updCmd.Parameters(0).Value = "CLOSED"
updCmd.Parameters(1).Value = "OPEN"
Else
Label1.Text = "OPEN"
Label1.Text = "CLOSED"
updCmd.Parameters(0).Value = "OPEN"
updCmd.Parameters(1).Value = "CLOSED"
End If
updCn.Open()
upCmd.ExecuteNonQuery()
End Using
End Using
End Using
End Sub
But the bigger question here is why you're going to the database twice at all?
Private Sub Label1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Label1.Click
Dim SQL As String = "UPDATE boomtable SET Tab1 = CASE WHEN Tab1='CLOSED' THEN 'OPEN' ELSE 'CLOSED' END;SELECT Tab1 FROM boomtable LIMIT 1;"
Using cn As New MySqlConnection(connectionString), _
cmd As New MySqlCommand(SQL)
cn.Open()
Label1.Text = CStr(cmd.ExecuteScalar())
End Using
End Sub
Now isn't that a whole lot neater?
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