如何使用dropdownlistfor设置所选值 [英] How do I set the selected value using dropdownlistfor

问题描述

大家好，



我有一个模型，应该使用下拉框更新其属性。我为它创建了一个viewmodel，以便在视图中享受模型绑定，但是当我启动编辑页面时，我之前选择的值没有显示。请传递哪些参数以确保在编辑页面启动时显示上一个选定项目。

请在下面查看我的视图模型，控制器和视图页面。



ViewModel

 命名空间 ProAssure.ICMS.Web.Models.Severity 
 {
  public   class  SeverityUpdateViewModel 
 {
  public  SelectList Criticality { set ;  get ; } 
 
 
  public  SeverityUpdateViewModel（SeverityUpdateDto severityUpdateDto）
 {
 List< SelectListItem> dummyList =  new  List< SelectListItem>（）; 
 
  foreach （ var  availableCriticality  in  severityUpdateDto.Criticality）
 {
  var  listItem =  new  SelectListItem（）
 {
 Text = availableCriticality.ToString（），
 Value = availableCriticality.ToString（）
，Selected = availableCriticality.ToString（）。Equals（severityUpdateDto.Selected。 ToString（））
 
}; 
 dummyList.Add（listItem）; 
} 
 
 此 .Criticality =  new  SelectList（dummyList，   Text，  Value，severityUpdateDto.Selected.ToString（））; 
} 
} 
} 

控制器

  public   async 任务< ActionResult>编辑（ int ？id）
 {
 SeverityUpdateViewModel severityUpdateViewModel =  new  SeverityUpdateViewModel（严重性） ）; 
 
  return 查看（severityUpdateViewModel）; 
} 
 

查看

 < span class =code-keyword><   div     class   =  form-group >  
 @ Html.LabelFor（model => model.Criticality，htmlAttributes：new {@class =control-label col-md-3}）
 < span class =code-keyword><   div     class   =  col-md-9 >  
 @ Html.DropDownListFor（model => model.Criticality，Model.Criticality，new {htmlAttributes = new {@class =form-control}}）
 @ Html.ValidationMessageFor（model => model.Criticality，，new {@class =text-danger }）
 <   / div  > ;  
 <   / div  >  
 

非常感谢

解决方案

这是我使用DropDownListFor方法填充和选择下拉菜单的方式：



包含下拉列表在模型中列为属性

 @ Html.DropDownListFor（model = >  model.AvailabilityCriticalID，Model.AvailabilityCriticalityList）

模型内部：

  public  IEnumerable< SelectListItem> AvailabilityCriticalityList 
 {
  get  
 {
 IEnumerable< SelectListItem>结果=（来自 x   GetAvailabilityCriticalityList（）
  select   new  SelectListItem（）{Text = x.ToString（），Value = x.AvailabilityCriticalityID.ToString（）}）; 
 
  return 结果; 
} 
} 
 

下拉列表中项目的选择是自动的。

Hi All,

I have a model that one its properties should be updated using a drop-down box. I created a viewmodel for it so as to enjoy model-binding at the view but my previously selected value is not showing when I launch the edit page. Please what parameters do I pass to ensure the previous selected item shows when the edit page is launched.
Please find below my view model, controller and view page.

ViewModel

namespace ProAssure.ICMS.Web.Models.Severity
{
    public class SeverityUpdateViewModel
    {
        public SelectList Criticality { set; get; }


        public SeverityUpdateViewModel(SeverityUpdateDto severityUpdateDto)
        {
            List<SelectListItem> dummyList = new List<SelectListItem>();

            foreach (var availableCriticality in severityUpdateDto.Criticality)
            {
                var listItem = new SelectListItem()
                {
                    Text = availableCriticality.ToString(),
                    Value = availableCriticality.ToString()
                  , Selected = availableCriticality.ToString().Equals(severityUpdateDto.Selected.ToString())

                };
                dummyList.Add(listItem);
            }

            this.Criticality = new SelectList(dummyList, "Text", "Value", severityUpdateDto.Selected.ToString());
        }
    }
}

Controller

public async Task<ActionResult> Edit(int? id)
{
    SeverityUpdateViewModel severityUpdateViewModel = new SeverityUpdateViewModel(severity);

    return View(severityUpdateViewModel);
}

View

<div class="form-group">
    @Html.LabelFor(model => model.Criticality, htmlAttributes: new { @class = "control-label col-md-3" })
    <div class="col-md-9">
        @Html.DropDownListFor(model => model.Criticality, Model.Criticality, new { htmlAttributes = new { @class = "form-control" } })
        @Html.ValidationMessageFor(model => model.Criticality, "", new { @class = "text-danger" })
    </div>
</div>

Thank you very much

解决方案

This is the way I have used the DropDownListFor method to fill and select drop downs:

Include the drop down list in the model as a property

@Html.DropDownListFor(model => model.AvailabilityCriticalID, Model.AvailabilityCriticalityList)

Inside the model:

public IEnumerable<SelectListItem> AvailabilityCriticalityList
{
    get
    {
        IEnumerable<SelectListItem> Results = (from x in GetAvailabilityCriticalityList()
                                               select new SelectListItem() { Text = x.ToString(), Value = x.AvailabilityCriticalityID.ToString() });

        return Results;
    }
}

The selection of the item in the drop down is automatic.

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