Inlining Stephen Muecke's answer to [MVC5 Razor html.dropdownlistfor set selected when value is in array][1]

>Unfortunately `@Html.DropDownListFor()` behaves a little differently than other helpers when rendering controls in a loop. This has been previously reported as an issue on CodePlex (not sure if its a bug or just a limitation)

>The are 2 options to solve this to ensure the correct option is selected based on the model property

>---

>### **Option 1**  - Use an `EditorTemplate`

>Create a custom `EditorTemplate` for the type in the collection. Create a partial in `/Views/Shared/EditorTemplates/AggregationLevelConfiguration.cshtml` (note the name must match the name of the type


> 
    
>     @model yourAssembly.AggregationLevelConfiguration
    @Html.DropDownListFor(m => m.HelperCodeType, (SelectList)ViewData["CodeTypeItems"])
    .... // other properties of AggregationLevelConfiguration

> and then in the main view, pass the `SelectList` to the `EditorTemplate` as `additionalViewData`

> 

>     @using (Html.BeginForm())
    {
      ...
      @Html.EditorFor(m => m.Configurations , new { CodeTypeItems = Model.CodeTypeItems })
      ...

>---

>### **Option 2** - Generate a new `SelectList` in each iteration and set the `selectedValue`

>In this option your property `CodeTypeItems` should to be `IEnumerable<GenericIdNameType>`, not a `SelectList` (or just make `codeTypes` a public property). Then in the main view

> 

>     @Html.DropDownListFor(m => m.Configurations[0].HelperCodeType, new SelectList(Model.CodeTypeItems, "Id", "Name", Model.Configurations[0].HelperCodeType)

>**Side note**: there is no need to use `new { id = "Configurations[0].HelperCodeType"` - the `DropDownListFor()` method already generated that `id` attribute


Note: Also double check that you don't have other non-list related binding issues as described in these questions:

* [Html.DropdownListFor selected value not being set][2]
* [DropDownListFor Not Selecting Value][3]

[1]: https://stackoverflow.com/a/37411482/1366033
[2]: https://stackoverflow.com/q/19476530/1366033
[3]: https://stackoverflow.com/q/2278056/1366033

I have problems to set the default selected value of a DropDownList with DropDownListFor in ASP MVC 4.

When the property which I want to preselect is in a list it's never selected by default as expected.

Here is my code reduced to the important stuff:

Models:

    public class Renter
    {
	    ...
	    public virtual List<RentLine> RentLines { get; set; }
	    ...
	
        public Renter()
	    {
		    ...
            RentLines = new List<RentLine>();
		    ...
        }
    }
    
    public class RentLine
    {
        ...
        public Guid RenterId { get; set; }
        public virtual Renter Renter { get; set; }	
        public Guid GarageId { get; set; }
        public virtual Garage Garage { get; set; }
        ...
        
        public RentLine()
        {
            //
            // Testcase for default value in dropdownlist
            //
            GarageId = new Guid("e926dcac-05ac-4fc1-92a2-014345e6e11c");
        }
    }

Controller:

    public ActionResult Hinzufuegen()
    {
        var model = new AddRenterViewModel();
        return View(model);
    }

ViewModel:

	public class AddRenterViewModel
	{
		public Renter Renter { get; set; }
		
		public List<SelectListItem> RentableGarageItems { get; set; }
		
		...
		
		public AddRenterViewModel()
		{
			Renter = new Renter();
			Renter.RentLines.Add(new RentLine());
			
			RentableGarageItems = new List<SelectListItem>();
			foreach (var garage in Singleton.Instance.Entities.GetRentableGarages().OrderBy(g => g.No))
			{
				RentableGarageItems.Add(new SelectListItem{Text = garage.No.ToString(), Value = garage.Id.ToString()});
			}
		}	
	}

View:

	@model Grossgaragenverwaltung.ViewModels.AddRenterViewModel
	...
	Garage Nr. @Html.DropDownListFor(m => m.Renter.RentLines[0].GarageId, Model.RentableGarageItems) @* No selected value *@
			   @Html.TextBoxFor(m => m.Renter.RentLines[0].GarageId) @* Shows the id 'e926dcac-05ac-4fc1-92a2-014345e6e11c' as set in the constructor *@
	...

Here is the result, no selected value:

	Garage Nr.
	<select id="Renter_RentLines_0__GarageId" name="Renter.RentLines[0].GarageId" data-val-required="Das Feld "GarageId" ist erforderlich." data-val="true">
	<option value="225a761d-7d12-4e02-9d72-d54fb6934f05">1</option>
	<option value="d28fb4fb-d65b-4674-90d6-a4ab9636be80">2</option>
	<option value="e06b520b-e876-4870-b321-dc65f77967a7">3</option>
	<option value="56832d98-aa5a-4e1a-af44-2d7e00f2bb3a">4</option>
	<option value="551f1fa9-13a5-40ce-b795-50063e605027">5</option>
	<option value="bace4b40-92ab-4757-9716-2a2878c2c9e8">6</option>
	<option value="f9baf45b-96bf-463e-a234-a1522bfc9b9b">7</option>
	<option value="91d1d866-6346-4ab0-b2aa-35b56eeaf2b0">8</option>
	<option value="62eb3727-eab2-4180-90cd-7dc59119f44e">9</option>
	<option value="59768097-c772-4421-b907-a24397a106f5">10</option>
	<option value="270acf6b-e4e3-41c3-86dd-4381a313848a">11</option>
	<option value="923269cd-1ead-4346-90ce-6344acda5b1b">12</option>
	<option value="981ee61e-408b-4b08-a7d3-26c909f04a9d">13</option>
	<option value="f1c5043c-fe41-4a8e-8c58-e88363885de4">14</option>
	<option value="e926dcac-05ac-4fc1-92a2-014345e6e11c">15</option>
	<option value="5577dc00-7cfa-4bcd-99ad-3f356e4325ae">16</option>
	</select>
	<input id="Renter_RentLines_0__GarageId" type="text" value="e926dcac-05ac-4fc1-92a2-014345e6e11c" name="Renter.RentLines[0].GarageId">

How can i get this work?

UPDATE:
Here is a working example where everything works like expected, the problem occurs only in the case you see above:


	public class Renter
	{
		...
		public Salutation Salutation { get; set; }
		...

		public Renter()
		{
			...
			Salutation = Salutation.Male;
			...
		}
	}

	public ActionResult Hinzufuegen()
	{
		var model = new AddRenterViewModel();
		return View(model);
	}

	public class AddRenterViewModel
	{
		public Renter Renter { get; set; }

		public List&lt;SelectListItem&gt; SalutationItems { get; set; }

		...

		public AddRenterViewModel()
		{
			Renter = new Renter();
			Renter.RentLines.Add(new RentLine());

			SalutationItems = new List&lt;SelectListItem&gt;();
			foreach (Salutation salutation in Enum.GetValues(typeof(Salutation)))
			{
			   SalutationItems.Add(new SelectListItem { Text = NameEnum.GetName(salutation), Value = salutation.ToString() });
			}
		}   
	}

	@Html.DropDownListFor(m =&gt; m.Renter.Salutation, Model.SalutationItems)

	&lt;select id="Renter_Salutation" name="Renter.Salutation" data-val-required="Das Feld "Salutation" ist erforderlich." data-val="true"&gt;
	&lt;option value="Company"&gt;Firma&lt;/option&gt;
	&lt;option value="Male" selected="selected"&gt;Männlich&lt;/option&gt;
	&lt;option value="Female"&gt;Weiblich&lt;/option&gt;
	&lt;/select&gt;
