Index was out of bound array exeption in Mysql - mysql

Question

I have MySQL table for storing user details which contain 3 columns namely "UserName" ,"password" ,"Access Level". when i try to load details in to VB.net variables it shows " Index was out of bound arrray" Exeption
I am new to mysql please help
I have tried to change the index value of mysqldatareader()
DBConnectionMySql()
myCommandMySql.Connection = myConnectionMySql
myConnectionMySql.Open()
'-----
myCommandMySql.CommandText = "select * from tbl_userregistration where UserName = '" & Trim(Username_TextBox.Text) & "'"
myDataReaderMySql = myCommandMySql.ExecuteReader
If myDataReaderMySql.Read() = Nothing Then
MessageBox.Show("Invalide User Name you Enter!", "Username/Password checker", MessageBoxButtons.OK, MessageBoxIcon.Warning)
Username_TextBox.Focus()
Else
If Username_TextBox.Text = myDataReaderMySql(1) And Password_TextBox.Text = myDataReaderMySql(2) Then
user = Username_TextBox.Text
username = Username_TextBox.Text
Weighing_frm.Show()
Me.Visible = False
Me.Refresh()
Else
MessageBox.Show("Invalide Username Or Password please check and Re-Login!", "Username/Password checker", MessageBoxButtons.OK, MessageBoxIcon.Warning)
Username_TextBox.Focus()
when i try to log in in vb.net form from the loaded data "Index was outside the bounds of the array" error message was shown

Answer 1

Keep you data objects local so you can be sure they are closed and disposed. A Using...End Using block ensures this even if there is an error. You can make your connection string a form level variable so you can use it anywhere but that is the only form level variable you need.
You can pass your connection string directly to the constructor of the connection.
You can pass your sql command text and the connection directly to the constructor of the command.
Please always use Parameters. Not only will it save you from misplacing quotes but it will help ensure that correct datatypes are sent to the database. The most important thing is it helps protect you database from sql injection which can destroy your database. I had to guess at the datatypes in your database. Check the database and adjust the code accordingly.
The DataReader.Read method returns a Boolean so, checking if it returns Nothing is not a valid test. Boolean is a value type so it always returns True or False, never Nothing.
The username is always going to match because that is what you sent to the database in the where clause. As noted in comments by #Jimi, the indexes for the fields returned by the data reader start at 0 so, username would be 0, password 1 and, access level 2. Almost all collections in .net start at index 0.
Why are you using 2 different variables with the same value?
user = Username_TextBox.Text
username = Username_TextBox.Text
What is this supposed to do?
Me.Refresh()
In a real application you would NEVER store passwords as plain text. They would be salted and hashed.
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Using cn As New MySqlConnection("Your connection string")
Using cmd As New MySqlCommand("select * from tbl_userregistration where UserName = #UserName;", cn)
cmd.Parameters.Add("#UserName", MySqlDbType.Text).Value = Trim(Username_TextBox.Text)
cn.Open()
Using dr = cmd.ExecuteReader
If dr.HasRows Then
dr.Read()
If Password_TextBox.Text = myDataReaderMySql(1) Then
user = Username_TextBox.Text
Weighing_frm.Show()
Me.Visible = False
Else
MessageBox.Show("Invalide Username Or Password please check and Re-Login!", "Username/Password checker", MessageBoxButtons.OK, MessageBoxIcon.Warning)
Username_TextBox.Focus()
End If
Else
MessageBox.Show("Invalid User Name you Enter!", "Username/Password checker", MessageBoxButtons.OK, MessageBoxIcon.Warning)
Username_TextBox.Focus()
End If
End Using
End Using
End Using
End Sub