如何在MVC3中回发时为DropDown设置默认值

Question

我正在使用MVC3，并且我有一个下拉列表，我需要从数据库中设置默认值。

当我在下拉列表中选择一个值时，我得到一个回传，并且我选择的值甚至在回发之后被选中。我如何获得默认值，< - 在回发后再次选择项目 - >作为选定值？这是如何在MVC中完成的？

下面是我使用的控制器和视图。

我的模型

namespace BugTracker.Models 
{ 
    public class BugModel 
    { 
     public List<BugModel> InsertBug {get; set;} 
     public List<BugModel> Bugs { get; set; } 
     public Int16 BugID { get; set; } 
     [Required(ErrorMessage = "Title is required")] 
     public string Title { get; set; } 
     [Required(ErrorMessage = "Description is required")] 
     public string Description {get; set;} 
     [Required(ErrorMessage = "Version is required")] 
     public string Version { get; set; } 
     [Required(ErrorMessage = "BuildNumber is required")] 
     public string BuildNumber { get; set; } 
     [Required(ErrorMessage = "CreatedDate is required")] 
     public string CreatedDate { get; set; } 
     [Required(ErrorMessage = "GetDate is required")] 
     public string GetDate { get; set; } 

     public List<BugModel> GetProjects { get; set; } 
     public int ProjectID { get; set; } 
     [Required(ErrorMessage = "ProjectName is required")] 
     public string ProjectName { get; set; } 

     public List<BugModel> GetEmployee {get; set;} 
     public int EmployeeID { get; set; } 
     public int CreatedByID { get; set; } 
     [Required(ErrorMessage = "EmployeeName is required")] 
     public string EmployeeName {get;set;} 
     [Required(ErrorMessage = "CreatedBy is required")] 
     public string CreatedBy { get; set; } 

     public List<BugModel> GetCategory { get; set;} 
     public int CategoryID { get; set; } 
     [Required(ErrorMessage = "Category is required")] 
     public string Category { get; set;} 

     public List<BugModel> GetSeverity { get; set;} 
     public int SeverityID { get; set; } 
     [Required(ErrorMessage = "Severity is required")] 
     public string Severity { get; set; } 

     public List<BugModel> GetPriority { get; set; } 
     public int PriorityID { get; set; } 
     [Required(ErrorMessage = "Prirority is required")] 
     public string Prirority { get; set;} 

     public List<BugModel> GetReleasePhase { get; set;} 
     public int ReleasePhaseID { get; set; } 
     [Required(ErrorMessage = "ReleasePhase is required")] 
     public string ReleasePhase { get; set;} 

     public List<BugModel> GetTypes { get; set; } 
     public int TypeID { get; set; } 
     [Required(ErrorMessage = "Type is required")] 
     public string Type { get; set; } 
public List<BugModel> GetBugHistory { get; set; }  
     [Required(ErrorMessage = "AssignTo is required")] 
     public string AssignTo { get; set; } 

    } 
} 

我的控制器是

[AcceptVerbs(HttpVerbs.Post)]  
public ActionResult BugDetails(FormCollection form,string Projects,string Prirority,string CreatedBy,BugModel model)  
{ 
    var modelList = new List();  
    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();    
      conn.Close();    
      return View(modelList); 
     } 
    }  

我的视图页面是

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--")%> 
} 

当第e页面从回发返回，我想要选择默认值，但在MVC中没有页面加载方法。所以，请有人指出我正确的方向。

预先感谢您。

Answer 1

通过使用DropDownListFor（），您可以将想要的项目传递到您的视图中的模型。

实施例：

@{ var projects= (IEnumerable<Projects>)ViewBag.Projects; } 


@Html.DropDownListFor(m => m.ProjectId, projects, string.Empty) 

总之，使用模型来确定在下拉列表所选择的值，提供通过您的viewbag可能值。 如果您的模型上的属性是属性类型的默认值，则dropdownlistfor将显示带有可能值的列表的第一个值。