อยากให้ช่วยดูโค๊ด insert ให้หน่อยค่ะ มันเออเรอร์ ไม่ยอม insert ให้ ไม่ทราบผิดตรงไหนค่ะ

Imports System.Data
Imports System.Data.SqlClient

Public Class Register
    Dim sqlcon As SqlConnection
    Dim ds As DataSet
    Dim da As SqlDataAdapter

    Private Sub Register_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        sqlcon = New SqlConnection("Data Source=XXXXXXXXX;Initial Catalog=DVDRent;Integrated Security=True")

        If sqlcon.State = ConnectionState.Closed Then
            sqlcon.Open()
        End If
    End Sub

    Private Sub btmreturnok_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btmreturnok.Click




            Dim str As String = "INSERT INTO Employees (id,pass,fname,lname,mobi,rank) VALUES ('" & txtuserregis.Text.Trim & "','" & txtpasswordregis.Text.Trim & "','" & txtfname.Text.Trim & "','" & txtlname.Text.Trim & "','" & txtmobi.Text.Trim & "','" & ComboBoxpos.SelectedItem.Trim & "')"
            Dim com As New SqlCommand(str, sqlcon)
            Dim dr As SqlDataReader = com.ExecuteReader()
            If dr.HasRows Then
                dr.Read()
            Else
                MessageBox.Show("Complete")
            End If
            dr.Close()
        End If

    End Sub
End Class