How to set the Default value for DropDown when post back

When I select a value in the dropdownlist I get a postback and the value I selected is selected even after the postback. How do I get the default value, <--Select Project--> as selected value again after the postback? in mvc how do i do this plz help me

myn controlers like this

[AcceptVerbs(HttpVerbs.Post)]
        public ActionResult BugDetails(FormCollection form,string Projects,string  Prirority,string CreatedBy,BugModel model)
        {
            var modelList = new List<bugmodel>();
            ViewBag.Projects = new SelectList(GetProjects(), "ProjectId", "ProjectName");
            ViewBag.Prirority = new SelectList(GetPriority(), "PriorityID", "Prirority");
            ViewBag.CreatedBy = new SelectList(GetEmployee(), "EmployeeID", "EmployeeName");
            using (SqlConnection conn = new SqlConnection(@"Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=BugtrackerNew;Data Source=SSDEV5-HP\SQLEXPRESS"))
            {
                SqlCommand dCmd = new SqlCommand("Filter", conn);
                dCmd.CommandType = CommandType.StoredProcedure;                
                conn.Open();
                dCmd.Parameters.Add(new SqlParameter("@ProjectID", Projects));
                dCmd.Parameters.Add(new SqlParameter("@PriorityID",Prirority));
                dCmd.Parameters.Add(new SqlParameter("@CreatedByID",CreatedBy));
                SqlDataAdapter da = new SqlDataAdapter(dCmd);
                DataSet ds = new DataSet();
                da.Fill(ds);
                for (int i = 0; i <= ds.Tables[0].Rows.Count - 1; i++)
                {
                        model.BugID = Convert.ToInt16(ds.Tables[0].Rows[i]["BugID"]);
                        model.Title = ds.Tables[0].Rows[i]["Title"].ToString();
                        model.Description = ds.Tables[0].Rows[i]["Description"].ToString();
                        model.ProjectName = ds.Tables[0].Rows[i]["ProjectName"].ToString();
                        model.Version = ds.Tables[0].Rows[i]["Version"].ToString();
                        model.BuildNumber = ds.Tables[0].Rows[i]["BuildNumber"].ToString();
                        model.Category = ds.Tables[0].Rows[i]["Category"].ToString();
                        model.CreatedDate = ds.Tables[0].Rows[i]["CreatedDate"].ToString();
                        model.Severity = ds.Tables[0].Rows[i]["Severity"].ToString();
                        model.Prirority = ds.Tables[0].Rows[i]["Priorities"].ToString();
                        model.ReleasePhase = ds.Tables[0].Rows[i]["ReleasePhase"].ToString();
                        model.Type = ds.Tables[0].Rows[i]["Types"].ToString();
                        model.CreatedBy = ds.Tables[0].Rows[i]["CreatedByID"].ToString();
                        model.AssignedTo = ds.Tables[0].Rows[i]["AssignedTo"].ToString();
                        model.Status = ds.Tables[0].Rows[i]["ToStatus"].ToString();
                        modelList.Add(model);
                    }             
                conn.Close();             
                return View(modelList);
            }
        }


myn view page is 


 using (Html.BeginForm())
                         { %>  
                         
                            <%: Html.DropDownList("Projects", (SelectList)ViewBag.Projects)%>                           

                               <%: Html.DropDownList("Prirority", (SelectList)ViewBag.Prirority, "Select Project")%>  
                                             

                               <%: Html.DropDownList("CreatedBy", (SelectList)ViewBag.CreatedBy, "--Select Project--")%></bugmodel>

Tags: MVC3