I am trying to delete the users username from the database when s/he logs out. My code is the following which doesn't work. I Think it may have something to do with the connection string (database, password thing)
Private Sub Button1_Click_1(sender As System.Object, e As System.EventArgs) Handles Button1.Click
Dim Query As String
Dim con As MySqlConnection = New MySqlConnection("Server=localhost;User ID=root;Password=*Mypassword*;Database=myusers")
con.Open()
Query = "Delete FROM users WHERE name =" + loginuser.Text
'Table = users
'Name = Varchar(20)
'loginuser.text = Name (username)
Dim cmd As MySqlCommand = New MySqlCommand(Query, con)
MsgBox(Query)
Dim i As Integer = cmd.ExecuteNonQuery()
If (i > 0) Then
MsgBox("Record is Successfully Deleted")
Else
MsgBox("Record is not Deleted")
End If
con.Close()
End Sub
You are not enclosing name value with quotes in your sql string,
Ex: Delete FROM users WHERE name = 'abcname'
Change your code to use parameters which is clean and secure way to pass values and you don't have to worry about quotes when working with string parameters
Query = "Delete FROM users WHERE name = #name"
Dim cmd As MySqlCommand = New MySqlCommand(Query, con)
MySqlCommand.Parameters.AddWithValue("#name",loginuser.Text)
String literals need to be enclosed in single quotes so your query should be:
Query = "Delete FROM users WHERE name = '" + loginuser.Text + "'"
Also concatenating a string into a SQL statement opens you up to SQL injection attacks (or even just think about someone putting "O'Brien" as the login name). You should always use parameters instead.
Related
I want parameterize some SQL Statements so my code isn't vunerable to SQL Injections any longer But i have actually no plan how to parameterize for example a where clause.
Dim accID As String = DatabaseConnecter.readField("SELECT ID FROM accounts WHERE accountname ='" & user & "' AND password='" & pw & "';")
The Problem is if you type in a given username, for example test and extend the username with. You can log in without entering the password into the Application.
Edit:
Public Function readField(ByVal sql As String) As String
Dim output As String = "ERROR"
Using cn = New MySqlConnection(connString.ToString())
Using cmd = New MySqlCommand(sql, cn)
cn.Open()
Using rd = cmd.ExecuteReader()
Try
rd.Read()
output = rd.GetString(0)
rd.Close()
Catch ex As Exception
End Try
End Using
cn.Close()
End Using
End Using
Return output
End Function
ยดยดยด
To have a parameterized query you need to create parameters and write a proper SQL text where, in place of values typed directly from your user, you have parameter placeholders.
So, for example, you sql text should be something like this
Dim sqlText = "SELECT ID FROM accounts WHERE accountname =#name AND password=#pwd"
Now you have a parameterized text, but stil we need to create the parameters that will be sent to the database engine together with your sql command.
You can create the parameter (two in this case) in this way before calling the method that executes the query
Dim p1 as MySqlParameter = new MySqlParameter("#name", MySqlDbType.VarChar)
p1.Value = user
Dim p2 as MySqlParameter = new MySqlParameter("#pwd", MySqlDbType.VarChar)
p2.Value = password
Dim pms As List(Of MySqlParameter) = new List(Of MySqlParameter)()
pms.Add(p1)
pms.Add(p2)
Now we need to pass this list to your method (and this requires changes to your method signature)
DatabaseConnecter.readField(sqlText, pms)
The method itself should change to something like
Public Function readField(ByVal sql As String, Optional pms As List(Of MySqlParameter) = Nothing) As String
Dim output As String = "ERROR"
Using cn = New MySqlConnection(connString.ToString())
Using cmd = New MySqlCommand(sql, cn)
cn.Open()
' This block adds the parameter defined by the caller to the command
' The parameters are optional so we need to check if we have really received the list or not
if pms IsNot Nothing Then
cmd.Parameters.AddRange(pms.ToArray())
End If
Using rd = cmd.ExecuteReader()
Try
rd.Read()
output = rd.GetString(0)
rd.Close()
Catch ex As Exception
End Try
End Using
' no need to close when inside a using block
' cn.Close()
End Using
End Using
Return output
End Function
The method now has an optional parameter that will contain the list of the parameters required by the query (or nothing if your query doesn't require parameters). This list is added to the command parameters collection and the query is now executed.
Final Note: Storing passwords in clear text into a database is a well known security problem. I suggest you to search about how to store passwords in a database.
Private Function GetID(User As String, pw As String) As String
Using cmd As New SqlCommand("SELECT ID FROM accounts WHERE accountname =#user AND password=#password", New SqlConnection(SQLConnString))
cmd.Parameters.AddWithValue("#user", User)
cmd.Parameters.Add("#password", SqlDbType.NVarChar)
cmd.Parameters("#password").Value = pw
Try
cmd.Connection.Open()
Return cmd.ExecuteScalar()
Catch ex As Exception
'handle error
Return Nothing
Finally
cmd.Connection.Close()
End Try
End Using
End Function
I've demostrated two methods of setting the parameters. Search for more info or comparison.
I want to be able to read a value (in this case an Group ID). All the topics and tutorials I've watched/read take the data and put it into a textbox.
I don't want to put it in a textbox in this case; I want to grab the Group ID and then say:
If Group ID = 4 then login
Here is an image of the database.
Basically, but none of the tutorials I watch or the multiple forums. None of them take a a value and say if value = 4 then login or do something else.
If text = "1" Then
MysqlConn = New MySqlConnection
MysqlConn.ConnectionString =
"server='ip of server'.; username=; password=; database="
Dim READER As MySqlDataReader
Dim member_group_id As String
Try
MysqlConn.Open()
Dim Query As String
Query = "SELECT * FROM `core_members` where name='" & TextBox2.Text & "'"
Query = "SELECT * FROM `nexus_licensekeys` where lkey_key='" & TextBox1.Text & "'"
COMMAND = New MySqlCommand(Query, MysqlConn)
READER = COMMAND.ExecuteReader
Dim count As Integer
count = 0
While READER.Read
count = count + 1
End While
Here is what I have so far. I'm kind of new implementing mysql data with visual basic and only recently started to get into it. I'm not sure what comes next or how to even start with reading the group id etc.
As I said any help from here on out would be highly appreciated of how to read the group id and say if this group id = this number then do this or that. I'm sure you get the idea.
I divided the code into UI Sub, and Data Access Function that can return data to the UI. Your Event procedure code should be rather brief and the functions should have a single purpose.
Keep your database objects local to the method. This way you can have better control. The Using...End Using blocks ensure that your database objects are closed and disposed even if there is an error.
I leave it to you to add validation code. Checking for empty TextBox or no return of records.
I hope this serves as a quick introduction to using ADO.net. The take away is:
Use Parameters
Make sure connections are closed. (Using blocks)
Private ConnString As String = "server=ip of server; username=; password=; database="
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim GroupID As String = GetGroupID(TextBox1.Text)
If GroupID = "4" Then
'your code here
End If
Dim LocalTable As DataTable = GetLicenseKeysData(TextBox1.Text)
'Get the count
Dim RowCount As Integer = LocalTable.Rows.Count
'Display the data
DataGridView1.DataSource = LocalTable
End Sub
Private Function GetGroupID(InputName As String) As String
'Are you sure member_group_id is a String? Sure looks like it should be an Integer
Dim member_group_id As String = ""
'You can pass the connection string directly to the constructor of the connection
Using MysqlConn As New MySqlConnection(ConnString)
'If you only need the value of one field Select just the field not *
'ALWAYS use parameters. See comment by #djv concerning drop table
Using cmd As New MySqlCommand("SELECT g_id FROM core_members where name= #Name")
'The parameters are interperted by the server as a value and not executable code
'so even if a malicious user entered "drop table" it would not be executed.
cmd.Parameters.Add("#Name", MySqlDbType.VarChar).Value = InputName
MysqlConn.Open()
'ExecuteScalar returns the first column of the first row of the result set
member_group_id = cmd.ExecuteScalar.ToString
End Using
End Using
Return member_group_id
End Function
Private Function GetLicenseKeysData(InputName As String) As DataTable
Dim dt As New DataTable
Using cn As New MySqlConnection(ConnString)
Using cmd As New MySqlCommand("SELECT * FROM `nexus_licensekeys` where lkey_key= #Name;", cn)
cmd.Parameters.Add("#Name", MySqlDbType.VarChar).Value = InputName
cn.Open()
dt.Load(cmd.ExecuteReader())
End Using
End Using
Return dt
End Function
I'm working on a project that needs to prevent double username inserted in a database my code looks like this:
Command = New MySqlCommand("Select * From userscanner", Connection)
Command.ExecuteNonQuery()
Dim dr As MySqlDataReader
dr = Command.ExecuteReader
With dr
.Read()
Dim check As String = .Item(1)
.Close()
If check = txtbox_username.Text Then
MsgBox("Username Already Taken")
Exit Sub
My problem is it only gets 1 column or is there any other way to prevent double username in my database?
I need all column in my username column. I'm using VB and MySQL.
You should ask your database if a particular user name exists or not.
This could be done with a WHERE clause
Dim sqlText = "SELECT 1 FROM userscanner WHERE username = #name"
Using Command = New MySqlCommand(sqlText, Connection)
Command.Parameters.Add("#name", MySqlDbType.VarChar).Value = txtbox_username.Text
Dim result = Command.ExecuteScalar()
if result IsNot Nothing Then
MsgBox("Username Already Taken")
End If
End Using
Here I assume that your database table named userscanner has a field named username (the field retrieved by your code with Item(1)) where you store the user names. Adding a WHERE condition and a simple return of 1 if there is a record allows to use the simple ExecuteScalar that returns the value 1 if there is a matching record to your textbox value or Nothing if there is no record
I found an answer to the question on my own.
Command = New MySqlCommand("Select * From userscanner WHERE Username = '" & txtbox_username.Text & "'", Connection)
Command.ExecuteNonQuery()
Dim dr As MySqlDataReader
dr = Command.ExecuteReader
dr.Read()
dr.Close()
If dr.HasRows Then
MsgBox("Username Already Taken")
Thanks for the help guys
Ok from the answer from the previous question the reasoning still applies here but this time A different issue. There is a login system (Loginvb.vb) that I got for the launcher I was creating and was wondering 2 things:
Is there a better way to do the Login check with the database (as in
more secure) (the login style will have a web based registration
setting via PHP script)?
Is there a way to take a certain column (labled as access) in the database and put it
as a public string so I can check if it will equal 1 2 or 3 in a
different form labeled as Main.vb
Here is the current login check:
Public Sub login_Click(sender As Object, e As EventArgs) Handles login.Click
If txtuserName.Text = "" Or txtpassWord.Text = "" Then
MsgBox("You cannot progress until you login....(moron =p)")
Else
'Connects To the Database
Dim connect As MySqlConnection
connect = New MySqlConnection()
connect.ConnectionString = "server=127.0.0.1;user id=sc;Password=derp;database=sclaunch" 'not the actual login ;)
Try
connect.Open()
Catch myerror As MySqlException
MsgBox("Error Connecting to Database. Please Try again !")
End Try
'SQL Query To Get The Details
Dim myAdapter As New MySqlDataAdapter
Dim sqlquerry = "Select * From login where username = '" + txtuserName.Text + "' And password= '" + txtpassWord.Text + "'"
Dim myCommand As New MySqlCommand()
'My fail attempt at what I am trying to do :(
Dim sql22 As MySqlConnection
sql22 = New MySqlConnection()
sql22.ConnectionString = "Select * From login where access ="
'End of fail attempt
myCommand.Connection = connect
myCommand.CommandText = sqlquerry
'Starting The Query
myAdapter.SelectCommand = myCommand
Dim mydata As MySqlDataReader
mydata = myCommand.ExecuteReader
'To check the Username and password and to validate the login
If mydata.HasRows = 0 Then
MsgBox("Invalid Login")
Else
'fail testing xD
Label3.Text = sql22
MsgBox("You are now Loged In!")
End If
End If
End Sub
Still basically learning more and more as I am coding all this got to love trial and error and the moments where you get stuck =/ (Sorry to the admins or whatever for fixing tag issues still new to the site xD)
Assuming that the same table login that contains the credentials contains also the access column that you want to retrieve, then I have changed a lot of your code
Dim sqlquerry = "Select * From login where username = #name AND password=#pwd"
Dim myCommand As New MySqlCommand(sqlquery, connect)
myCommand.Parameters.AddWithValue("#name", txtuserName.Text)
myCommand.Parameters.AddWithValue("#pwd", txtpassWord.Text)
Dim mydata = myCommand.ExecuteReader
If mydata.HasRows = False Then
MsgBox("Invalid Login")
Else
' the same record that contains the credentials contains the access field'
mydata.Read()
Label3.Text = mydata("access").ToString()
MsgBox("You are now Loged In!")
End If
What I have changed:
Removed the string concatenation and added the appropriate parameters
Removed myAdapter and every references to it (not needed, you don't
fill DataTable/DataSet)
Removed sql22 and every references to it. It's a Connection and you
try to use like a Command
Fixed the check on HasRows (Returns a boolean not an integer. Are you
using Option Strict Off?)
Why won't this delete the data in my MySQL database!?
Private Sub Button4_Click(sender As System.Object, e As System.EventArgs) Handles Button4.Click
Dim dbCon As MySqlConnection
Dim strQuery As String = ""
Dim SQLCmd As MySqlCommand
Dim DR As MySqlDataReader
Try
dbCon = New MySqlConnection("Server=Localhost;Database=myusers;Uid=root;Pwd=Mypassword")
strQuery = "DELETE settings FROM settings WHERE user=" & Me.loginuser.Text
'* FROM settings WHERE user = "Testuser"'
SQLCmd = New MySqlCommand(strQuery, dbCon)
' OPEN THE DB AND KICKOFF THE QUERY
dbCon.Open()
DR = SQLCmd.ExecuteReader
While DR.Read
req1.Text = "" And exlink.Text = ""
End While
' DONE! Close DB
DR.Close()
dbCon.Close()
Catch ex As Exception
TextBox8.Text = ("Fail" & vbCrLf & vbCrLf & ex.Message)
End Try
Here is a picture of my database:
Alternatively I could somehow make it replace what is already in the database, in which case please help me with that.
Try
strQuery = "DELETE FROM settings " _
& " WHERE user = '" & Me.loginuser.Text & "'"
but as was stated earlier, you should be using parameterized queries. If you had a user named O'Brien then your query (as composed above) would fail because of the embedded single quote. When you use DELETE, you are deleting entire records and you already specify the table name in the FROM clause.
I will try to change your code in this way
Using con = New MySqlConnection("Server=.....")
con.Open()
Dim sqlText = "DELETE * FROM settings WHERE user = #ulogin"
Using cmd = new MySqlCommand(sqlText, con)
cmd.Parameters.AddWithValue("#ulogin", Me.loginuser.Text)
cmd.ExecuteNonQuery()
End Using
End Using
First and foremost, do not use string concatenation to create command texts to pass to the database engine. In that way you risk Sql Injections, also, if the user name contains a single quote (i.e. O'Hara) your code will fail with a syntax error (Same problems arise for date formatting, parsing numeric decimals and other globalization issues). Instead a parametrized query like the one in code above will avoid all of these problems.
In a parametrized query, the text of the query doesn't contains the actual value for the search condition or the update or insert data. Instead it contains placeholders ( in our case it is called #ulogin). The correct value to insert at the placeholders position is specified using one or more MySqlParameter added to the Parameters collection of the MySqlCommand. In this case I have used the AddWithValue method that derives the correct datatype directly from the datatype of the value. Because Me.loginuser.Text is a string value then the parameter will be treated as a string value replacing incorrect single quotes and removing extraneus characters usually used to Mount Sql Injections Attacks. The engine will do the rest inserting the correct value at the placeholder at execution time
EDIT: Seeing your comment about the MySql connector used, I will try to update my answer to show a semi-equivalent version for NET 1.
Try
Dim con As MySqlConnection = New MySqlConnection("Server=.....")
con.Open()
Dim sqlText as String = "DELETE * FROM settings WHERE user = #ulogin"
Dim cmd As MySqlCommand = new MySqlCommand(sqlText, con)
Dim par As MySqlParameter = New MySqlParameter("#ulogin", MySqlDbType.VarChar)
par.Value = Me.loginuser.Text
cmd.Parameters.Add(par)
cmd.ExecuteNonQuery()
Finally
con.Close()
End Try
I am not sure if the connector 1.0.10 supports the parameter name with the # prefix or just the : prefix
i dont think you can use double quotes in mysql, i think its single quotes only. try
Query = "DELETE * FROM settings WHERE user = '" & Me.loginuser.Text & "'"