SelectExtensions.DropDownList Method (HtmlHelper, String, IEnumerable<SelectListItem>, String, Object)

项目
02/21/2011

Returns a single-selection select element using the specified HTML helper, the name of the form field, the specified list items, an option label, and the specified HTML attributes.

Namespace: System.Web.Mvc.Html
Assembly: System.Web.Mvc (in System.Web.Mvc.dll)

Syntax

'Declaration
<ExtensionAttribute> _
Public Shared Function DropDownList ( _
    htmlHelper As HtmlHelper, _
    name As String, _
    selectList As IEnumerable(Of SelectListItem), _
    optionLabel As String, _
    htmlAttributes As Object _
) As MvcHtmlString

public static MvcHtmlString DropDownList(
    this HtmlHelper htmlHelper,
    string name,
    IEnumerable<SelectListItem> selectList,
    string optionLabel,
    Object htmlAttributes
)

[ExtensionAttribute]
public:
static MvcHtmlString^ DropDownList(
    HtmlHelper^ htmlHelper, 
    String^ name, 
    IEnumerable<SelectListItem^>^ selectList, 
    String^ optionLabel, 
    Object^ htmlAttributes
)

Parameters

htmlHelper
Type: System.Web.Mvc.HtmlHelper
The HTML helper instance that this method extends.

name
Type: System.String
The name of the form field to return.

selectList
Type: System.Collections.Generic.IEnumerable<SelectListItem>
A collection of SelectListItem objects that are used to populate the drop-down list.

optionLabel
Type: System.String
The text for a default empty item. This parameter can be null reference (Nothing in Visual Basic).

htmlAttributes
Type: System.Object
An object that contains the HTML attributes to set for the element.

Return Value

Type: System.Web.Mvc.MvcHtmlString
An HTML select element with an option subelement for each item in the list.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type HtmlHelper. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).

Exceptions

Exception	Condition
ArgumentException	The name parameter is null reference (Nothing in Visual Basic) or empty.

Remarks

The DropDownList method renders an element that enables the user to select one item from a drop-down list. Each item in the list is a SelectListItem object.

The difference between calling the DropDownList method and using a select element is that the DropDownList method is designed to make it easy to bind to view data or model data.

The htmlAttributes parameter consists of an object that contains name/value pairs. The attributes that are specified in the name/value pairs depend on the HTML element that is being rendered. For example, for a select element, you might provide the following anonymous object:

new { id = "select1", size="8" }

New With { .id = "select1",.size="8" }

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