การเลือกค่าทั้งหมดจาก Combobox ต้องทำยังไงคะ ใช้SelectedIndexChangedได้รึปล่าวคะ

Private Sub cbosite_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cbosite.SelectedIndexChanged

        sb = New StringBuilder
        sb.Append("SELECT * FROM STAFF")
        sb.Append(" WHERE Site_code like '" & (cbosite.SelectedIndex).ToString & "'")
        connection()
        da = New SqlDataAdapter(sb.ToString, conn)
        ds = New DataSet
        For i = 0 To da.Fill(ds, "Site") - 1
            cbosite.Properties.Items.Add(ds.Tables("Site").Rows(i)("site_name").ToString)
            site_Code.Add(ds.Tables("Site").Rows(i)("Site_code").ToString)
            site_id.Add(ds.Tables("Site").Rows(i)("Site_id").ToString)
        Next
        da.Fill(ds, "STAFF")
        GridControl1.DataSource = ds.Tables("STAFF")
        format_grid()
        conn.Close()

        
    End Sub