VB insert records in database

Imports System.Data.SqlClient
Imports System.Windows
Imports System.Xml

Public Class Form1

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim Username = txtUserName.Text
        Dim phone = txtPhone.Text
        Dim add = txtAddress.Text
        Dim comments = txtComments.Text

        Dim connetionString As String
        Dim connection As SqlConnection
        Dim adapter As SqlDataAdapter
        Dim ds As New DataSet
        Dim sql As String

        Try

            connetionString = "Data Source=(local);Initial Catalog=cand;User ID=test;Password=test"
            connection = New SqlConnection(connetionString)

            connection.Open()


            sql = "Insert Into person values ('" & txtUserName.Text & "','" & txtPhone.Text & "' , '" & txtAddress.Text & "', '" & txtComments.Text & "') "

            adapter = New SqlDataAdapter(sql, connection)
            adapter.Fill(ds)

            Dim insert As New SqlCommand(sql, connection)

            insert.Parameters.AddWithValue(Username, txtUserName.Text)
            insert.Parameters.AddWithValue(phone, txtPhone.Text)
            insert.Parameters.AddWithValue(add, txtAddress.Text)
            insert.Parameters.AddWithValue(comments, txtComments.Text)

            insert.ExecuteNonQuery()

            MsgBox("Successfully Saved")
            Me.Visible = False

        Catch ex As Exception

            MessageBox.Show(ex.Message)


        End Try

    End Sub

    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        Dim connetionString As String
        Dim connection As SqlConnection
        Dim adapter As SqlDataAdapter
        Dim ds As New DataSet
        Dim sql As String

        connetionString = "Data Source=(local);Initial Catalog=cand;User ID=test;Password=test"
        connection = New SqlConnection(connetionString)
        sql = "select * from person"
        Try
            connection.Open()
            adapter = New SqlDataAdapter(sql, connection)
            adapter.Fill(ds)
            connection.Close()
            ds.WriteXml("Person.xml")
            MsgBox("Done")
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try

    End Sub
End Class