이 ASP.NET MVC SelectList를 작동 시키려면 어떻게해야합니까?

이 ASP.NET MVC SelectList를 작동 시키려면 어떻게해야합니까?

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컨트롤러에 selectList를 작성하여 뷰에 표시합니다.

나는 그것을 즉석에서 만들려고 노력하고 있습니다.

myViewData.PageOptionsDropDown = 
   new SelectList(new [] {"10", "15", "25", "50", "100", "1000"}, "15");

컴파일되지만 출력이 좋지 않습니다 ...

<select id="PageOptionsDropDown" name="PageOptionsDropDown">
    <option>10</option>
    <option>15</option>
    <option>25</option>
    <option>50</option>
    <option>100</option>
    <option>1000</option>
</select>

선택된 항목이 없는지 확인하십시오.

이 문제를 어떻게 해결할 수 있습니까?

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이것이 내가하는 방법입니다

IList<Customer> customers = repository.GetAll<Customer>();
IEnumerable<SelectListItem> selectList = 
    from c in customers
    select new SelectListItem
    {
        Selected = (c.CustomerID == invoice.CustomerID),
        Text = c.Name,
        Value = c.CustomerID.ToString()
    };

언뜻보기에 당신이 무엇을하는지 잘 모르겠습니다 ...

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확장 방법을 사용합니다.

용법

var departmentItems = departments.ToSelectList(d => d.Code + 
                                               " - " + d.Description,
                                               d => d.Id.ToString(),
                                               " - ");

var functionItems = customerFunctions.ToSelectList(f => f.Description, 
                                                   f => f.Id.ToString(), 
                                                   " - ");

와

public static class MCVExtentions
{
    public static List<SelectListItem> ToSelectList<T>(
        this IEnumerable<T> enumerable, 
        Func<T, string> text, 
        Func<T, string> value, 
        string defaultOption)
    {
        var items = enumerable.Select(f => new SelectListItem()
                                     {
                                         Text = text(f), 
                                         Value = value(f) 
                                     }).ToList();
        items.Insert(0, new SelectListItem()
                    {
                        Text = defaultOption, 
                        Value = "-1" 
                    });
        return items;
    }
}

---

items, dataValueField, dataTextField, selectedValue매개 변수로 허용되는 생성자를 사용하여 :

ViewData["myList"] = 
                new SelectList(new[] { "10", "15", "25", "50", "100", "1000" }
                .Select(x => new {value = x, text = x}), 
                "value", "text", "15");

그렇다면 당신의 관점에서 :

<%=Html.DropDownList("myList") %>

---

Thomas Stock의 답변을 바탕으로 다음과 같은 오버로드 된 ToSelectList메소드를 만들었습니다 .

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web.Mvc;

public static partial class Helpers
{
    public static IEnumerable<SelectListItem> ToSelectList<T>(this IEnumerable<T> enumerable, Func<T, object> value, bool selectAll = false)
    {
        return enumerable.ToSelectList(value, value, selectAll);
    }

    public static IEnumerable<SelectListItem> ToSelectList<T>(this IEnumerable<T> enumerable, Func<T, object> value, object selectedValue)
    {
        return enumerable.ToSelectList(value, value, new List<object>() { selectedValue });
    }

    public static IEnumerable<SelectListItem> ToSelectList<T>(this IEnumerable<T> enumerable, Func<T, object> value, IEnumerable<object> selectedValues)
    {
        return enumerable.ToSelectList(value, value, selectedValues);
    }

    public static IEnumerable<SelectListItem> ToSelectList<T>(this IEnumerable<T> enumerable, Func<T, object> value, Func<T, object> text, bool selectAll = false)
    {
        foreach (var f in enumerable.Where(x => x != null))
        {
            yield return new SelectListItem()
            {
                Value = value(f).ToString(),
                Text = text(f).ToString(),
                Selected = selectAll
            };
        }
    }

    public static IEnumerable<SelectListItem> ToSelectList<T>(this IEnumerable<T> enumerable, Func<T, object> value, Func<T, object> text, object selectedValue)
    {
        return enumerable.ToSelectList(value, text, new List<object>() { selectedValue });
    }

    public static IEnumerable<SelectListItem> ToSelectList<T>(this IEnumerable<T> enumerable, Func<T, object> value, Func<T, object> text, IEnumerable<object> selectedValues)
    {
        var sel = selectedValues != null
            ? selectedValues.Where(x => x != null).ToList().ConvertAll<string>(x => x.ToString())
            : new List<string>();

        foreach (var f in enumerable.Where(x => x != null))
        {
            yield return new SelectListItem()
            {
                Value = value(f).ToString(),
                Text = text(f).ToString(),
                Selected = sel.Contains(value(f).ToString())
            };
        }
    }
}

컨트롤러에서 다음을 수행 할 수 있습니다.

var pageOptions = new[] { "10", "15", "25", "50", "100", "1000" };
ViewBag.PageOptions = pageOptions.ToSelectList(o => o, "15" /*selectedValue*/);

마지막으로보기에 다음을 입력하십시오.

@Html.DropDownList("PageOptionsDropDown", ViewBag.PageOptions as IEnumerable<SelectListItem>, "(Select one)")

원하는 결과가 나옵니다. 물론 "(Select one)"첫 번째 빈 항목을 원하지 않으면 위 의 optionLabel을 생략 할 수 있습니다 .

<select id="PageOptionsDropDown" name="PageOptionsDropDown">
<option value="">(Select one)</option>
<option value="10">10</option>
<option selected="selected" value="15">15</option>
<option value="25">25</option>
<option value="50">50</option>
<option value="100">100</option>
<option value="1000">1000</option>
</select>

Update: A revised code listing can be found here with XML comments.

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The problem is, SelectList works as designed. The bug is in the design. You may set the Selected Property in SelectedItem, but this will completely be ignored, if you traverse the list with the GetEnumerator() (or if Mvc does that for you). Mvc will create new SelectListItems instead.

You have to use the SelectList ctor with the SelectListItem[], the Text-Name, the Value-Name and the SelectedValue. Be aware to pass as SelectedValue the VALUE of SelectListItem, which you want to be selected, not the SelectListItem itself! Example:

SelectList sl = new SelectList( new[]{
  new SelectListItem{ Text="one", Value="1"},
  new SelectListItem{ Text="two", Value="2"},
  new SelectListItem{ Text="three", Value="3"}
}, "Text", "Value", "2" );

(not tested this, but I had the same problem)

then the 2nd option will get the selected="selected" attribute. That looks like good old DataSets ;-)

---

This is an option:

myViewData.PageOptionsDropDown = new[] 
{
 new SelectListItem { Text = "10", Value = "10" },
 new SelectListItem { Text = "15", Value = "15", Selected = true }
 new SelectListItem { Text = "25", Value = "25" },
 new SelectListItem { Text = "50", Value = "50" },
 new SelectListItem { Text = "100", Value = "100" },
 new SelectListItem { Text = "1000", Value = "1000" },
}

---

If that's literally all you want to do then just declaring the array as string fixes the selected item problem:

myViewData.PageOptionsDropDown = 
   new SelectList(new string[] {"10", "15", "25", "50", "100", "1000"}, "15");

---

It's very simple to get SelectList and SelectedValue working together, even if your property isn't a simple object like a Int, String or a Double value.

Example:

Assuming our Region object is something like this:

public class Region {
     public Guid ID { get; set; }
     public Guid Name { get; set; }
}

And your view model is something like:

public class ContactViewModel {
     public DateTime Date { get; set; }
     public Region Region { get; set; }
     public List<Region> Regions { get; set; }
}

You can have the code below:

@Html.DropDownListFor(x => x.Region, new SelectList(Model.Regions, "ID", "Name")) 

Only if you override the ToString method of Region object to something like:

public class Region {
     public Guid ID { get; set; }
     public Guid Name { get; set; }

     public override string ToString()
     {
         return ID.ToString();
     }
}

This have 100% garantee to work.

But I really believe the best way to get SelectList 100% working in all circustances is by using the Equals method to test DropDownList or ListBox property value against each item on items collection.

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It seems if you have a strongly typed view you need to change the ID of the dropdown so that it is NOT the name of a property on the inherrited class. You then need to put some logic in your edit (POST) method to pull off the selected value from the FORMCollection and put it on to your instance before committing your changes.

This is certainly a little strange, but i tried it and it works.

So if you class has a field called CountryId say, and you're displaying a list of country names, make the dropdown have an id of CountryName rather than CountryId, then in the post, you can do something with Collection["CountryName"].

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I had the exact same problem. The solution is simple. Just change the "name" parameter passed to the DropDownList helper to something that does not match any of the properties existing in your ViewModel. read more here: http://www.dotnetguy.co.uk/post/2009/06/25/net-mvc-selectlists-selected-value-does-not-get-set-in-the-view

I quote the Dan Watson:

In MVC if the view is strongly typed the selectlist’s selected option will be overridden and the selected option property set on the constructor will never reach the view and the first option in the dropdown will be selected instead (why is still a bit of a mystery).

cheers!

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All these answers look great, but seems to be that the controller is preparing data for a View in a well-known structured format vs. letting the view simply iterate an IEnumerable<> delivered via the model and build a standard select list then let DefaultModelBinder deliver the selected item back to you via an action parameter. Yes, no, why not? Separation of concerns, yes? Seems odd to have the controller to build something so UI and View specific.

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Simple:

string[] someName = new string[] {"10", "15", "25", "50", "100", "1000"};
myViewData.PageOptionsDropDown = new SelectList(someName, "15");

---

I just ran it like this and had no problems,

public class myViewDataObj
    {
        public SelectList PageOptionsDropDown { get; set; }
    }

public ActionResult About()
        {
            myViewDataObj myViewData = new myViewDataObj();
            myViewData.PageOptionsDropDown =
                  new SelectList(new[] { "10", "15", "25", "50", "100", "1000" }, "15");

            ViewData["myList"] = myViewData.PageOptionsDropDown;
            return View();
        }

and

<%=Html.DropDownList("myList") %>

it also worked if you do this,

public ActionResult About()
        {
            myViewDataObj myViewData = new myViewDataObj();
            myViewData.PageOptionsDropDown =
                  new SelectList(new[] { "10", "15", "25", "50", "100", "1000" });

            ViewData["myListValues"] = myViewData.PageOptionsDropDown;
            ViewData["myList"] = "15";
            return View();
        }

and

<%=Html.DropDownList("myList",(IEnumerable<SelectListItem>)ViewData["myListValues"]) %>

---

Using your example this worked for me:

controller:

ViewData["PageOptionsDropDown"] = new SelectList(new[] { "10", "15", "25", "50", "100", "1000" }, "15");

view:

<%= Html.DropDownList("PageOptionsDropDown")%>

---

MonthRepository monthRepository = new MonthRepository();
IQueryable<MonthEntity> entities = monthRepository.GetAllMonth();
List<MonthEntity> monthEntities = new List<MonthEntity>();

foreach(var r in entities)
{
    monthEntities.Add(r);
}

ViewData["Month"] = new SelectList(monthEntities, "MonthID", "Month", "Mars");

---

I do it like this:

List<SelectListItem> list = new List<SelectListItem>{
new SelectListItem {Selected = true, Text = "Select", Value = "0"},
new SelectListItem {Selected = true, Text = "1", Value = "1"},
new SelectListItem {Selected = true, Text = "2", Value = "2"}
};
return list.ToArray();

The ToArray() takes care of the problems.

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If you want to pass some random text to your DropDownList, for example --Select-- you can easy do this using this code:

@Html.DropDownListFor(x => x.CategoryId, new SelectList(Model.Categories, "Id", "Name"), "--Select--", new { @class = "form-control" })

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It may be the case that you have some ambiguity in your ViewData:

Take a look Here

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the value selected in the model takes advantage instead of the default item. (I agree I didn't read all posts)

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I can't remember how mvc 1 was setup, but it seems that it wanted the select list named the same as the field it belonged too...

What I found, as someone kind of said above, is that my select lists weren't working in mvc2 when the ViewData they were sent as was named the same as the field.

For example:

<%= Html.DropDownListFor((model => model.ForID), (SelectList)ViewData["ForName"]) %>

works when

<%= Html.DropDownListFor((model => model.ForID), (SelectList)ViewData["ForID"]) %>

does not work as the ViewData name "ForID" is named the same as the field it is working for

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A possible explanation is that the selectlist value that you are binding to is not a string.

So in that example, is the parameter 'PageOptionsDropDown' a string in your model? Because if it isn't then the selected value in the list wouldn't be shown.

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If you look in the source code for MVC 2 at the Html.DropDownList extension method, it never checks the SelectList class SelectedValue property. It will only ever try to match against your Model.

All the above are all variations on a theme, ie how do you send a bunch of data to the view to for a drop-down list & they're all as good as each other (more-or-less).

The problem is in the view. Either create your own DropDownList extension method that does respect the selectvalue you set, or iterate though by hand. Which ever works best for you.

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If you have a collection in your model and your View is strongly type, some variation of this will work:

@Html.DropDownListFor(x => x.RegionID, 
    new SelectList(Model.Regions,"RegionID", "RegionName", Model.RegionID))

-or-

@Html.DropDownList("RegionID", 
    new SelectList(Model.Regions, "RegionID", "RegionName", Model.RegionID))

참고URL : https://stackoverflow.com/questions/781987/how-can-i-get-this-asp-net-mvc-selectlist-to-work