下拉不工作MVC C＃剃刀

Question

我有一个页面，有3个下拉列表，客户，项目和设施。 当第一次加载页面时，我可以将这些值加载到数据库的下拉列表中。

更改客户端中的选定值应该基于所选客户端加载新项目，改变所选项目的相同方式应加载属于选定项目的新设施。

当我更改客户端值时，项目和设施加载正常，甚至认为所选客户端未显示在下拉列表中。但是当我改变项目或设施似乎没有发生时，所有选定的值都会返回0。 这里是CSHTML代码

@using (Html.BeginForm("Index", "Home")) { 
    @Html.DropDownListFor(x => x.SelectedClientId, new SelectList(Model.Clients, "PrimaryKey", "Name", Model.SelectedClientId), "--Select Client--", new { onchange = "this.form.submit();" }); 
} 
@using (Html.BeginForm("Index", "Home")) { 
    @Html.DropDownListFor(y => y.SelectedProjectId, new SelectList(Model.Projects, "PrimaryKey", "Name", Model.SelectedProjectId), "--Select Project--", new { onchange = "this.form.submit();" }) 
} 
@using (Html.BeginForm("Index", "Home")) { 
    @Html.DropDownListFor(z => z.SelectedFacilityId, new SelectList(Model.Facilities, "PrimaryKey", "Name", Model.SelectedFacilityId), "--Select Facility--", new { onchange = "this.form.submit();" }) 
} 

这里是IndexViewModel

public class IndexViewModel { 
    public int SelectedClientId { get; set; } 
    public BusinessEntityCollection<Client> Clients { get; set; } 

    public int SelectedProjectId { get; set; } 
    public BusinessEntityCollection<Project> Projects { get; set; } 

    public int SelectedFacilityId { get; set; } 
    public BusinessEntityCollection<Facility> Facilities { get; set; } 
} 

这里是HomeController的

public ActionResult Index(IndexViewModel model) { 

BusinessEntityCollection<Client> clients = new BusinessEntityCollection<Client>(); 
BusinessEntityCollection<Project> projects = new BusinessEntityCollection<Project>(); 
BusinessEntityCollection<Facility> facilities = new BusinessEntityCollection<Facility>(); 

clients = ClientController.GetClients(); 

if (Request.HttpMethod == "POST") { 
    Session["SelectedClientId"] = model.SelectedClientId; 
    Session["SelectedProjectId"] = model.SelectedProjectId; 
    Session["SelectedFacilityId"] = model.SelectedFacilityId; 

    if (Session["SelectedClientId"] == null) { 
     projects.Add(new Project() { Name = "None", PrimaryKey = 0 }); 
    } 
    else { 
     if (Convert.ToInt32(Session["SelectedClientId"]) == 0) { 
      projects = ProjectController.GetUserProjects(clients[0].PrimaryKey); 
      Session["SelectedClientId"] = clients[0].PrimaryKey; 
     } 
     else 
      projects = ProjectController.GetUserProjects(Convert.ToInt32(Session["SelectedClientId"])); 
    } 

    if (Session["SelectedProjectId"] == null) { 
     facilities.Add(new Facility() { Name = "None", PrimaryKey = 0 }); 
    } 
    else { 
     if (Convert.ToInt32(Session["SelectedProjectId"]) != 0) 
      facilities = FacilityController.GetFacilitiesByProject(Convert.ToInt32(Session["SelectedProjectId"])); 
    } 
} 

model.Clients = clients; model.Projects = projects; model.Facilities = facilities; 
return View(model); 

}

我想选择的值保存到会话变量和检索他们，但它似乎并没有工作。

Answer 1

对于所有三个下拉菜单，您都需要一个表单。并非每种形式。

@using (Html.BeginForm("Index", "Home")) { 
    @Html.DropDownListFor(x => x.SelectedClientId, new SelectList(Model.Clients, "PrimaryKey", "Name", Model.SelectedClientId), "--Select Client--", new { onchange = "this.form.submit();" }); 

    @Html.DropDownListFor(y => y.SelectedProjectId, new SelectList(Model.Projects, "PrimaryKey", "Name", Model.SelectedProjectId), "--Select Project--", new { onchange = "this.form.submit();" }) 

    @Html.DropDownListFor(z => z.SelectedFacilityId, new SelectList(Model.Facilities, "PrimaryKey", "Name", Model.SelectedFacilityId), "--Select Facility--", new { onchange = "this.form.submit();" }) 
}