Hashing passwords for a login form in vb.net - mysql

Question

I have a Login form, I haven't done anything about hashing the password yet, I have been reading about hash here and there yet it really confuses me and don't really know how to implement it in my code for the login form.
Code for hashing I saw
Dim bytes() as byte = System.Text.Encoding.UTF8.GetBytes(stringPassword);
dim hashOfBytes() as byte = new System.Security.Cryptography.SHA1Managed().ComputeHash(bytes)
Dim strHash as string = Convert.ToBase64String(hashOfBytes)
Convert back to bytes
hashOfBytes = Convert.FromBase64String(strHash)
** My Login Form Code**
Using conn As New MySqlConnection("Server = localhost; Username= root; Password =; Database = forms")
Using cmd
With cmd
MsgBox("Connection Established")
.Connection = conn
.Parameters.Clear()
.CommandText = "SELECT * FROM users WHERE BINARY Username = #iUsername AND Password = #iPassword"
.Parameters.Add(New MySqlParameter("#iUsername", txtUser.Text))
.Parameters.Add(New MySqlParameter("#iPassword", txtPass.Text))
End With
Try
conn.Open()
dr = cmd.ExecuteReader()
Catch ex As MySqlException
MsgBox(ex.Message.ToString())
End Try
End Using
End Using
If dr.HasRows = 0 Then
MsgBox("Invalid user")
Conn.Close()
Else
Start.Show()
Conn.Close()
End If
End Sub

Answer 1

You should store the hash value of the password in the Password field of your table.
Then you search for user and the password hash, not directly for the password taken from the input box.
However, your code will still fail because you try to use the MySqlDataReader after the disposing of the connection. Move the check for rows inside the Using block
Dim strHash as string = Convert.ToBase64String(hashOfBytes)
.....
Dim userIsValid as Boolean = False
Using conn As New MySqlConnection(.........)
Using cmd
....
.Parameters.Add(New MySqlParameter("#iPassword", strHashPass))
Try
conn.Open()
dr = cmd.ExecuteReader()
userIsValid = dr.HasRows
Catch ex As MySqlException
MsgBox(ex.Message.ToString())
End Try
End Using
End Using
if userIsValid then
.....
else
.....
End