reading and comparing data values in MySQL database in vb.net - mysql

Question

I'm trying to collect input from the user, check it against my database, and see if it exists in the database. If it does the program is supposed to fetch the last name, first name, and fees of the respective individual and output it.
Code:
Imports Mysql.Data.MySqlClient
Public Class Form1
Dim reader As MySqlDataReader
Dim command As New MySqlCommand
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim myConnectionString As String
myConnectionString = "server=localhost;" _
& "uid=root;" _
& "pwd=Emma#21*GCTU;" _
& "database=dummystudents"
Try
Dim conn As New MySql.Data.MySqlClient.MySqlConnection(myConnectionString)
conn.Open()
Dim sql As String = "SELECT idstudents FROM students WHERE idstudents = #TextBox1.Text "
command = New MySqlCommand(sql, conn)
reader = command.ExecuteReader()
If reader.Read() Then
TextBox2.Text = reader(1)
TextBox3.Text = reader(2)
TextBox4.Text = reader(3)
End If
Catch ex As MySql.Data.MySqlClient.MySqlException
MessageBox.Show(ex.Message)
End Try
End Sub
End Class

Answer 1

Here's your SQL code:
SELECT idstudents FROM students WHERE idstudents = #TextBox1.Text
What's the point of pulling idstudents out when that's the value you're putting in? Worse, though, that's ALL you're pulling out, then you do this:
TextBox2.Text = reader(1)
TextBox3.Text = reader(2)
TextBox4.Text = reader(3)
which would require you to pull back at least four columns.
The modification mentioned in the comments may well get your code to execute but it's not the right way to go. It looks like you tried to use a parameter but failed. Do that but do it right, i.e.
Dim sql As String = "SELECT idstudents, otherColumnsHere FROM students WHERE idstudents = #idstudents"
Using connection As New MySqlConnection(myConnectionString),
command As New MySqlCommand(sql, connection)
command.Parameters.Add("#idstudents", MySqlDbType.Int32).Value = CInt(TextBox1.Text)
conn.Open()
Using reader = command.ExecuteReader()
If reader.Read() Then
TextBox2.Text = reader(1)
TextBox3.Text = reader(2)
TextBox4.Text = reader(3)
End If
End Using
End Using