code behind file and the class

public class Transition
{
// default constructor   
    public Transition()
    {
        if (StageId == 0)
        {
_queryString = "SELECT PHASE, FROM_STAGE, TO_STAGE, END_REASON FROM     Dbase WHERE PHASE='Complaint'";
        }
        else if (StageId > 0)
        {
_queryString = string.Format("SELECT PHASE, FROM_STAGE, TO_STAGE, END_REASON FROM Dbase WHERE PHASE='Complaint' AND STAGE_FROM_ID={0}",StageId);
               
        }
     }
    
// getters and setters for quesry string
public string QueryString
        { 
            get { return _queryString; }
            set { _queryString = value;}
        }
// getters and setters for stage id
public int StageId
        {
    private get { return _stageId; }
            set { _stageId = value; }
        }
    
 
// The variables  
private string _queryString;
private int    _stageId;
private string _fillDropdownList;     

// This is where I call the class.

ublic partial class GridGroupControl : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
       
        
        Transition trns = new Transition();
        trns.StageId =1672;
        SqlDataSource1.SelectCommand = trns.QueryString;

    }