I want to connect my MySQL to my VB.net.
I am only using Login Form.
I have given the code but the code gives me this error message: Connection must be valid and open
This is my code:
Imports MySql.Data.MySqlClient
Public Class Login
Dim MysqlConn As MySqlConnection
Dim Command As MySqlCommand
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
MysqlConn = New MySqlConnection
MysqlConn.ConnectionString ="server=db4free.net;port=3306;userid=exd****;password=****;database=exd****"
Dim Reader As MySqlDataReader
Try
MysqlConn.Open()
Dim Query As String
Query = "select * from member where Username='" & UsernameTxt.Text & "' and Password='" & PasswordTxt.Text & "' "
Command = New MySqlCommand
Reader = Command.ExecuteReader
Dim count As Integer
count = 0
While Reader.Read
count = count + 1
End While
If count = 1 Then
MessageBox.Show("Correct !")
ElseIf count > 1 Then
MessageBox.Show("Duplicate !")
Else
MessageBox.Show("Not Correct !")
End If
MysqlConn.Close()
Catch ex As Exception
MsgBox(ex.Message)
Finally
MysqlConn.Dispose()
End Try
End Sub
End Class
Can anyone help me to fix that? Thanks.
To associate your Query and Command with the connection you need to do this:
Command = New MySqlCommand(Query, MysqlConn)
You can then perform operations to retrieve the data you need.
At no point do you associate your MysqlConn nor Query to your Command before trying to call ExecuteReader on it. As such, it doesn't have a valid connection at that time.
Query = "select * from member where Username='" & UsernameTxt.Text & "' and Password='" & PasswordTxt.Text & "' ", nombredelaconexion
Related
I am trying to make a little program that writes and reads from a Mysql database. The reading part is going well, but I am a bit stuck in the write part.
This is my code:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Absenden.Click
Dim conn As New MySqlConnection
Dim command As MySqlCommand
Dim myConnectionString As String
myConnectionString = "server=Nothing;uid=to;pwd=see;database=here;"
conn.ConnectionString = myConnectionString
Try
conn.Open()
Dim Querywrite As String
Querywrite = "select * FROM here.message INSERT INTO message admin='" & TB_Name.Text & "' and message='" & TB_Nachricht.Text & "' and Server='" & TB_Server.Text & "' and status='" & TB_Status.Text & "' "
command = New MySqlCommand(Querywrite, connection)
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
conn.Close()
End Sub
The Querywrite part is the problem I think. The input comes from Textboxes in a Windows Form.
Thanks for your help!
Perhaps, if someone shows you once then you will get the idea. The main thing is to always use parameters; not only will you avoid minor sytax and type errors but you will avoid major disasters of malicious input. I guessed at the datatypes of your fields. Please check your database for the types and adjust your code accordingly.
Private Sub InsertData()
Dim strQuery As String = "Insert Into message (admin, message, Server, status) Values (#admin, #message, #Server, #status);"
Using cn As New MySqlConnection("your connection string")
Using cmd As New MySqlCommand With {
.Connection = cn,
.CommandType = CommandType.Text,
.CommandText = strQuery}
cmd.Parameters.Add("#admin", MySqlDbType.VarString).Value = TB_Name.Text
cmd.Parameters.Add("#message", MySqlDbType.VarString).Value = TB_Nachricht.Text
cmd.Parameters.Add("#Server", MySqlDbType.VarString).Value = TB_Server.Text
cmd.Parameters.Add("#status", MySqlDbType.VarString).Value = TB_Status.Text
cn.Open()
cmd.ExecuteNonQuery()
cn.Close()
End Using
End Using
End Sub
I am trying to to add up the points a certain user has earned from a mysql database table
My code returns an error saying the syntax is incorrect, I can't figure out how to make it work>
Here is my code:
Imports MySql.Data.MySqlClient
Public Class Leaderboard
Dim MysqlConn As MySqlConnection
Dim COMMAND As MySqlCommand
Private Sub submitBtn_Click(sender As Object, e As EventArgs) Handles submitBtn.Click
MysqlConn = New MySqlConnection
MysqlConn.ConnectionString =
"server=localhost;userid=root;password=root99;database=database"
Dim READER As MySqlDataReader
Try
MysqlConn.Open()
Dim Query As String
Query = "select SUM(Points) * from database.progress where candidate_number_fk = '" & textbox_can.Text & "'"
COMMAND = New MySqlCommand(Query, MysqlConn)
READER = Command.ExecuteReader
MessageBox.Show("You have successfully submitted your score")
MysqlConn.Close()
Catch ex As MySqlException
MessageBox.Show(ex.Message)
Finally
MysqlConn.Dispose()
End Try
My.Forms.Menu1.Show()
Me.Hide()
End Sub
End Class
This is incorrect SQL syntax:
select SUM(Points) *
from database.progress
where . . .
Presumably, you intend:
select SUM(Points) as sumpoints
from database.progress
where . . .
You can then pull the field from the result set by name.
Note: There may be other problems with your code. This only addresses the SQL query.
The first part of the program, which reads the database works fine, the problem is with deleting. The database looks like: ID, Username and Text.
The code I'm currently using:
Public Class Form1
Dim dbCon As MySqlConnection
Dim strQuery As String = ""
Dim SQLCmd As MySqlCommand
Dim dr As MySqlDataReader
Private Sub Delete()
Try
dbCon = New MySqlConnection(Connection string)
strQuery = "Delete * FROM otletek WHERE id = " & TextBox2.Text
SQLCmd = New MySqlCommand(strQuery, dbCon)
dbCon.Open()
MsgBox(strQuery)
dbCon.Close()
Catch ex As Exception
MsgBox("Connection error" & vbCrLf & ex.Message)
End Try
End Sub
Are you missing the code that executes the SQL command?
SQLCmd.ExecuteNonQuery()
try this:
strQuery = "Delete FROM otletek WHERE id = " & TextBox2.Text
it's a SQL injection waiting to happen - bad idea.
How to Inserting Label.text data into mySql table.
i have no problem with textbox.text but i can't figure out how it with Label.text
i try the same code with textbox.text
parameterB_Answer.Value = TextBox1.Text
it work find but when i try with
parameterB_Answer.Value = Label1.Text
mySqlReader seems can't read it.
Update:
1.1.1 is label1.text. My Idea is to insert the text "1.1.1" from Label1 as Primary key and the Textbox(textbox1.text) as the following
my code is:
Try
Dim StrSQL As String = "INSERT INTO boranga" & _
"(IdBorangA,Answers)" & _
"VALUES (#B_IdA,#B_Answer);"
Dim myCommand As MySqlCommand = New MySqlCommand(StrSQL, conn.open)
myCommand.CommandType = CommandType.Text
Dim parameterB_IdA As MySqlParameter = New MySqlParameter("#B_IdA", MySqlDbType.VarChar, 300)
parameterB_IdA.Value = Label1.Text
Dim parameterB_Answer As MySqlParameter = New MySqlParameter("#B_Answer", MySqlDbType.VarChar, 300)
parameterB_Answer.Value = TextBox1.Text
With myCommand.Parameters
.Add(parameterB_IdA)
.Add(parameterB_Answer)
End With
Dim result As MySqlDataReader = myCommand.ExecuteReader(CommandBehavior.CloseConnection)
MsgBox("Tersimpan", vbYes, "boranga")
Catch SqlEx As MySqlException
Throw New Exception(SqlEx.Message.ToString())
End Try
but when I change the value of Label1.text (1.1.1) to 111, it works just fine. probably because I put INT for the column for label1.text to fill while "1.1.1" isn't integer
thank a lot
PS:seems i can't post image because low of reputation
Try using this code format first of all:
Private Sub btnLogin_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLogin.Click
Dim conn As MySqlConnection
'Connect to the database using these credentials
conn = New MySqlConnection
conn.ConnectionString = "server=your server site (generally long url); user id=login id for mysql user; password=self explanatory; database=name of the DB you're trying to reach"
'Try and connect (conn.open)
Try
conn.Open()
Catch myerror As MySqlException 'If it fails do this... (i.e. no internet connection, etc.)
MsgBox("Error connecting to database. Check your internet connection.", MsgBoxStyle.Critical)
End Try
'MySQL query (where to call for information)
Dim myAdapter As New MySqlDataAdapter
'Tell where to find the file with the emails/passes stored
Dim sqlquery = "SELECT * FROM the database you selected above WHERE Email = '" & txtEmail.Text & "' AND Password = '" & txtPassword.Text & "'"
Dim myCommand As New MySqlCommand
myCommand.Connection = conn
myCommand.CommandText = sqlquery
'Start query
myAdapter.SelectCommand = myCommand
Dim myData As MySqlDataReader
myData = myCommand.ExecuteReader
If myData.HasRows = 0 Then
MsgBox("Invalid email address or password.", MsgBoxStyle.Critical)
Else
MsgBox("Logged in as " & txtEmail.Text & ".", MsgBoxStyle.Information)
Me.Close()
End If
End Sub
And to insert label.text try replacing one of the textbox.text fields first and see if it will accept it. If it does, then the answer was all in the formatting.
Also, do not forget to call:
imports mysql.data.mysqlclient
and make sure to add the mysql.data reference.
when I input data are not yet available. button does not work
but when I enter existing data in the database, the button work for find existing records in the database and msgbox.appear
this my coding. (i am using Microsoft Visual Basic 2008 express edition database mysql)
Imports MySql.Data.MySqlClient
Public Class Form2
Public conn As MySqlConnection
Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Application.DoEvents()
Button1.Focus()
conn = New MySqlConnection
'conn.ConnectionString = "server=localhost;database=ilmu;userid=root;password= ''"
Try
conn.Open()
Catch ex As Exception
MessageBox.Show("Error1: " & ex.Message)
End Try
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
conn = New MySqlConnection("server=localhost;database=ilmu;userid=root;password= ''")
Try
conn.Open()
Dim sqlquery As String = "SELECT * FROM visitor WHERE nama = '" & TextBox1.Text & "';"
Dim data As MySqlDataReader
Dim adapter As New MySqlDataAdapter
Dim command As New MySqlCommand
command.CommandText = sqlquery
command.Connection = conn
adapter.SelectCommand = command
data = command.ExecuteReader
While data.Read()
If data.HasRows() = True Then
If data(2).ToString = TextBox2.Text Then
command = New MySqlCommand
command.Connection = conn
tkhupd = Now.ToString("yyyy-MM-dd HH:mm:tt")
command.CommandText = "INSERT INTO visitor(noK,khupd)VALUES ('" & TextBox1.Text & "','" & tkhupd & "')"
command.ExecuteNonQuery()
MessageBox.Show(" Berjaya, Sila Masuk. ", "Tahniah", MessageBoxButtons.OK, MessageBoxIcon.Information)
Else
MsgBox("exist")
End If
Else
MsgBox("Failed Login.")
End If
End While
Catch ex As Exception
End Try
End Sub
End Class
I am not sure what you are trying to do when there is not matching record in the database, but you don't have any code that would be hit in the case of no matching entries.
If there are no matching records, your while condition isn't met and nothing in the loop happens.
Fixing it likely involves rearranging the order of your loop and your if condition.
Check to see if data.hasRows first.
Example:
If data.HasRows() = True Then
While Data.Read
//code here for found rows
End While
Else
//code for no matching entries
End If
And as has been mentioned in Joel's comment, you really should look at using parameterized queries.
example of your insert command altered:
command.CommandText = "INSERT INTO visitor(noK,khupd)VALUES (?noK,?khupd)"
command.Parameters.AddWithValue("?noK",TextBox1.Text)
command.Parameters.AddWithValue("?khupd", tkhupd)
command.ExecuteNonQuery()