I'm new to Visual Basic, I am quite proficient in php which is why I moved on to VB. I am having trouble getting data and displaying it. Here's my full code which is supposed to look in my database "game", find the row with username "kenazz" and display the username "kenazz".
Imports MySql.Data.MySqlClient
Public Class Form1
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim cs As String = "Database=game;Data Source=localhost;" _
& "User Id=root;Password="
Dim conn As New MySqlConnection(cs)
Try
conn.Open()
Dim stm As String = "SELECT * FROM users WHERE users.username = 'Kenazz'"
Dim cmd As MySqlCommand = New MySqlCommand(stm, conn)
Dim reader As MySqlDataReader = cmd.ExecuteReader()
While reader.Read()
Console.WriteLine(reader.GetInt32("id") & ": " _
& reader.GetString("username"))
End While
reader.Close()
Catch ex As MySqlException
Console.WriteLine("Error: " & ex.ToString())
Finally
conn.Close()
End Try
End Sub
End Class
Where am I going wrong?
Related
I am trying to display value in combobox using MySQL in vb.net. Right now the problem that I am facing is that combobox is not displaying values from MySQL. I have the below code:
MySqlConn = New MySqlConnection
MySqlConn.ConnectionString = "server=localhost;userid=root;password=root;database=s974_db"
Try
MySqlConn.Open()
Label21.Text = "DB Connection Successful"
Dim Query As String
Query = "select * from s974_db.processors where Name='" & ComboBox1.Text & "'"
COMMAND = New MySqlCommand(Query, MySqlConn)
READER = COMMAND.ExecuteReader
While READER.Read
Label10.Text = READER.GetDouble("Price")
End While
MySqlConn.Close()
Catch ex As MySqlException
MessageBox.Show(ex.Message)
Finally
MySqlConn.Dispose()
End Try
However, using the above code Combobox1.Text returns nothing but if I use below code which has a different query it works:
MySqlConn = New MySqlConnection
MySqlConn.ConnectionString = "server=localhost;userid=root;password=root;database=s974_db"
Try
MySqlConn.Open()
Label21.Text = "DB Connection Successful"
Dim Query As String
Query = "select * from s974_db.processors"
COMMAND = New MySqlCommand(Query, MySqlConn)
READER = COMMAND.ExecuteReader
While READER.Read
Dim sName = READER.GetString("Name")
ComboBox1.Items.Add(sName)
End While
MySqlConn.Close()
Catch ex As MySqlException
MessageBox.Show(ex.Message)
Finally
MySqlConn.Dispose()
End Try
Could someone please check and let me know what could be the issue? Thanks!
so the highlights as i mentioned them in the comments
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
' You need only to open aconnection once
MySqlConn = New MySqlConnection
MySqlConn.ConnectionString = "server=localhost;userid=root;password=root;database=s974_db"
Try
MySqlConn.Open()
Label21.Text = "db connection successful"
'First load both Combobox
Dim query As String
query = "select * from s974_db.processors"
COMMAND = New MySqlCommand(query, MySqlConn)
READER = COMMAND.ExecuteReader
While READER.Read
Dim sname = READER.GetString("name")
ComboBox1.Items.Add(sname)
ComboBox2.Items.Add(sname)
End While
Catch ex As MySqlException
MessageBox.Show(ex.Message)
Finally
End Try
End Sub
Private Sub Form1_Closing(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Closing
Try
MySqlConn.Close()
MySqlConn.Dispose()
Catch ex As Exception
End Try
End Sub
ANd now the Comboboxes
Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) Handles ComboBox1.SelectedIndexChanged
'Only when there is a item selected , ask for data
If ComboBox1.SelectedIndex > -1 Then
Try
Dim Query As String
Query = "select * from s974_db.processors where Name='" & ComboBox1.Text & "'"
COMMAND = New MySqlCommand(Query, MySqlConn)
READER = COMMAND.ExecuteReader
While READER.Read
Label11.Text = READER.GetDouble("Price")
End While
Catch ex As MySqlException
MessageBox.Show(ex.Message)
Finally
End Try
End If
End Sub
Private Sub ComboBox2_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox2.SelectedIndexChanged
If ComboBox2.SelectedIndex > -1 Then
Try
Dim Query As String
Query = "select * from s974_db.processors where Name='" & ComboBox1.Text & "'"
COMMAND = New MySqlCommand(Query, MySqlConn)
READER = COMMAND.ExecuteReader
While READER.Read
Label10.Text = READER.GetDouble("Price")
End While
Catch ex As MySqlException
MessageBox.Show(ex.Message)
Finally
End Try
End If
End Sub
This is exactly as i described on Form_load you fill both comboboxes
When you now change one of the comboxes one of the label change too.
Sometimes you have to update the Element to see a change
in that case you write at the end of the loop
Label10.Update()
Starting at the top...
Keep your database objects local to the method where they are used. (Not Form level variables) You can make the connection string a class level string variable. This is the only way you can ensure that they are closed and disposed.
Using...End Using blocks will close and dispose your database objects even if there is an error. The constructor of the connection takes the connection string. Connections are precious objects. Don't open the connection until directly before the .Execute method and close it as soon as possible.
It doesn't make much sense that the user could select an item from ComboBox1 before the Form.Load.
In general, we don't want to download anymore data than necessary and we want to hit the database as little as possible. In the Form.Load we bind the combobox to a data table that contains the name and price fields, setting the display and value members. Now, whenever the user picks a name in the combo we can retrieve the price without connecting to the database again.
I noticed that you were using Val in another event. This is an old VB6 method that can give you unexpected results. .Net and vb.net have all sorts of ways to get numbers out of strings that are faster and more reliable. CInt, .TryParse, .Parse, CType, Convert.To etc.
Public Class Form1
Private ConString As String = "server=localhost;userid=root;password=root;database=s974_db"
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'Fill combobox
Dim dt As New DataTable
Using cn As New MySqlConnection(ConString),
cmd As New MySqlCommand("select Name, Price from processors;", cn)
cn.Open()
dt.Load(cmd.ExecuteReader)
End Using 'Closes and disposes both connection and command
ComboBox1.DataSource = dt
ComboBox1.DisplayMember = "Name"
ComboBox1.ValueMember = "Price"
End Sub
Private Sub ComboBox1_SelectionChangeCommitted(sender As Object, e As EventArgs) Handles ComboBox1.SelectionChangeCommitted
Label10.Text = ComboBox1.SelectedValue.ToString
ClearLabels()
End Sub
Private Sub ClearLabels()
Label11.Text = ""
Label12.Text = ""
Label13.Text = ""
Label14.Text = ""
Label15.Text = ""
Label16.Text = ""
Label17.Text = ""
Label18.Text = ""
Label19.Text = ""
Label20.Text = ""
End Sub
End Class
I'm trying to show image from mysql to PictureBox, and I set it to show on a form load. But when my form loads, picture doesn't appear, and the code shows no errors. Here's the code:
Private Sub frmStudentskiPanel_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Konekcija = New MySqlConnection
Konekcija.ConnectionString = "server=localhost; userid=root; password=masterzlaja123; database=proba"
Dim Command As MySqlCommand
Dim reader As MySqlDataReader
Dim img() As Byte
Try
Konekcija.Open()
Dim Query As String
Query = "Select Slika from proba.studenti where Korisnicko_ime = '" & Label2.Text & "' "
Command = New MySqlCommand(Query, Konekcija)
reader = Command.ExecuteReader
While reader.Read()
img = reader.Item("Slika")
Dim mstream As New MemoryStream(img)
PictureBox1.Image = Image.FromStream(mstream)
End While
Konekcija.Close()
Catch ex As Exception
MessageBox.Show(ex.Message)
Finally
Konekcija.Dispose()
End Try
End Sub
End Class
I'm trying to make a chat in Vb.net using MySQL and I want to load the chat into a list-box where would be the (username) ''par'' and the (message).
But it keeps showing me errors and i don't understand how to solve it.
Here's my code:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim stringConn As String
Dim stringCmd As String
Dim myConn As MySqlConnection
Dim myCmd As MySqlCommand
stringCmd = "SELECT par, message FROM chat"
stringConn = "server=localhost; user id=studio; password=mypw; database=studio;"
myConn = New MySqlConnection(stringConn)
myCmd = New MySqlCommand(stringCmd, myConn)
myConn.Open()
Dim myReader As MySqlDataReader
myReader = myCmd.ExecuteReader()
'Reset your List box here.
ListBox1.Items.Clear()
While myReader.Read()
--------------Here is my problem ---------------
ListBox1.Items.Add(myReader.GetString(1//username//) & " " & myReader.GetString(2//message//))
----end-- of the---problem---
End While
myReader.Close()
myConn.Close()
End Sub
You could try this:
If myReader.HasRows = True Then
Do While myReader.Read()
ListBox1.Items.Add(myReader(0) & " " & myReader(1))
Loop
End If
Best Regards
I have a program that takes info from the user and logs them into a database using Phpmyadmin, our code is the exact same, except for my friend he can't login.
Code is here:
Both our database name, tables and columns are the EXACT same, he can register the account to the DB so it stores it, but when he tries to login with the same information it says that it was unsuccessful.
SignUpForm(THIS WORKS)
Public Class frmSignup
Dim ServerString As String = "Server=localhost;User Id=root;Password=;Database=accountinfo"
Dim SQLConnection As MySqlConnection = New MySqlConnection
Private Sub Form3_Load(sender As Object, e As EventArgs) Handles MyBase.Load
SQLConnection.ConnectionString = ServerString
Try
If SQLConnection.State = ConnectionState.Closed Then
SQLConnection.Open()
MsgBox("Successfully connected to DB")
Else
SQLConnection.Close()
MsgBox("Failed to connect to DB")
End If
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Sub
Public Sub SaveAccountInformation(ByRef SQLStatement As String)
Dim cmd As MySqlCommand = New MySqlCommand
With cmd
.CommandText = SQLStatement
.CommandType = CommandType.Text
.Connection = SQLConnection
.ExecuteNonQuery()
End With
SQLConnection.Close()
SQLConnection.Dispose()
End Sub
Private Sub btnSignup_Click(sender As Object, e As EventArgs) Handles btnSignup.Click
If txtPasswd.Text = txtPasswd2.Text Then
MessageBox.Show("Passwords Match!")
Dim HashedPass As String = ""
'Converts the Password into bytes, computes the hash of those bytes, and then converts them into a Base64 string
Using MD5hash As MD5 = MD5.Create()
HashedPass = System.Convert.ToBase64String(MD5hash.ComputeHash(System.Text.Encoding.ASCII.GetBytes(txtPasswd.Text)))
End Using
Dim SQLStatement As String = "INSERT INTO accountinfodb(`Usernames`, `Passwords`) VALUES ('" & txtUsername.Text & "','" & HashedPass & "')"
SaveAccountInformation(SQLStatement)
MessageBox.Show("Account Successfully Registered")
frmLogin.Show()
frmLoginScreen.Hide()
Else
MessageBox.Show("Passwords Do Not Match!")
txtPasswd.Text = Focus()
txtPasswd.Clear()
txtPasswd2.Text = Focus()
txtPasswd2.Clear()
End If
End Sub
End Class
LOGIN FORM(THIS DOES NOT WORK FOR HIM BUT IT WORKS FOR ME)
Imports MySql.Data.MySqlClient
Imports System.Security.Cryptography
Public Class frmLogin
Private Sub btnLogin_Click(sender As Object, e As EventArgs) Handles btnLogin.Click
Dim conStr = "Server=localhost;User Id=root;Password=;Database=accountinfo"
Dim SQL = "SELECT * FROM accountinfodb WHERE Usernames = #uname AND `Passwords` = #pword"
Dim HashedPass As String = ""
'Converts the Password into bytes, computes the hash of those bytes, and then converts them into a Base64 string
Using MD5hash As MD5 = MD5.Create()
HashedPass = System.Convert.ToBase64String(MD5hash.ComputeHash(System.Text.Encoding.ASCII.GetBytes(txtPasswd.Text)))
End Using
' this object will be closed and dispose # End Using
Using dbCon As New MySqlConnection(conStr)
' the command object likewise
Using cmd As New MySqlCommand(SQL, dbCon)
dbCon.Open()
cmd.Parameters.Add(New MySqlParameter("#uname", txtUsername.Text))
cmd.Parameters.Add(New MySqlParameter("#pword", HashedPass))
' create a Using scope block for the reader
Using rdr As MySqlDataReader = cmd.ExecuteReader
If rdr.HasRows Then
MessageBox.Show("Welcome, " & txtUsername.Text)
frmProduct.Show()
Else
MessageBox.Show("Oops! Login unsuccessful!(Password/Username may be wrong, or the user may not exist!")
txtUsername.Clear()
txtUsername.Focus()
txtPasswd.Clear()
End If
End Using
End Using ' close/dispose command
End Using ' close/dispose connection
End Sub
End Class
WOULD ALSO LIKE TO MENTION
I shared my files over google drive with him, so he did not copy and paste any of the code. This is the exact same files from MY computer.
Ok I found the issue, he was using an outdated version of MySQL while my version was the most up to date. I reinstalled the proper MySQL server to the newest version and it worked!
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()