I want to show the firstname and familyname in a textbox in the main form.

I've got a registrationform with a firstname, familyname, username and password
After registration it is registrated in a tableregistration.
It's working fine to show the username into a textbox in the main form (see code)

How can I show the firstname and familyname in the textbox instead of the username


Code:
 Private Sub Btn_login_Click(sender As Object, e As EventArgs) Handles Btn_login.Click

        Dim cmd As New SqlCommand("select * from tableregistration where username = @username and password = @password ", con)

        con.Open()
        cmd.Parameters.Add("@username", SqlDbType.VarChar).Value = txtusername.Text
        cmd.Parameters.Add("@password", SqlDbType.VarChar).Value = txtpassword.Text

        Dim adapt As New SqlDataAdapter(cmd)

        Dim table As New DataTable
        adapt.Fill(table)

        con.Close()

        If table.Rows.Count() <= 0 Then

            MessageBox.Show("Username or password invalid 
                             or not yet registered !")

            txtusername.Text = ""
            txtpassword.Text = ""
            txtusername.Focus()

        Else

            ' It shows the username perfectly !

            MessageBox.Show("Welcome" & " " & txtusername.Text)
            Frm_main.TextBox1.Text = txtusername.Text
           
            Me.Close()
          
        End If

    End Sub
Thanks in advance.