razor Html.DropdownList提供“请选择”作为optionLabel，“US”作为selectedValue

Question

数据：

var countries = new Dictionary<string,string>();
countries.Add("AF","Afghanistan");
countries.Add("US","United States");
countries.Add("FR","France");

剃刀：

@Html.DropdownList("Countries",new SelectList(countries, "key", "value", "US"), "Select Country")

问题：在我的剃刀中，我为selectedValue指定了"US"，为optionLabel指定了"Select Country"。我希望这会插入"Select Country"作为下拉列表中的第一项，并且已经为我选择了"US"。

实际发生的事情："Select Country"已插入，但未选中"US"。 "Select Country"是。

问题：我可以同时拥有吗？ Razor注入"Please Select"，还预先选择"US"作为默认值？

请注意：我从数据库中的表中获取数据，所以我不希望在那里有“请选择”的实际行，或者必须插入它我自己进入字典。在我的控制器中更容易做模型.Countries = dbRepo.GetCountries（），而不是声明一个空字典，添加“请选择”，然后通过.GetCountries（）循环并添加到原始字典，然后再将其设置为Model.Countries我的观点。

谢谢！

Answer 1

这应该有效。不知道为什么它没有，因为你没有显示你的实际代码。可能在您的实际数据集中没有key = "US"的选项。

但无论如何，让我举一个例子来说明我建议的方法是使用视图模型和强类型帮助器DropDownListFor帮助器。

型号：

public class CountriesViewModel
{
    public string SelectedCountryCode { get; set; }
    public IEnumerable<SelectListItem> Countries { get; set; }
}

控制器：

public class HomeController : Controller
{
    public ActionResult Index()
    {
        var model = new CountriesViewModel();
        // TODO: obviously those will come from your database
        model.Countries = new[]
        {
            new SelectListItem { Value = "AF", Text = "Afghanistan" },
            new SelectListItem { Value = "US", Text = "United States" },
            new SelectListItem { Value = "FR", Text = "France" },
        };

        // Preselect the option with Value = "US"
        // Make sure you have such option in the Countries list
        model.SelectedCountryCode = "US";
        return View(model);
    }
}

查看（~/Views/Home/Index.cshtml）：

@model CountriesViewModel

@Html.DropDownListFor(
    x => x.SelectedCountryCode,
    Model.Countries, 
    "Select Country"
)

结果：

Answer 2

对于寻找国家/地区列表的人来说，这将有所帮助

var countries = new[]
                {
                    new SelectListItem { Value = "AF", Text = "AFGHANISTAN"}, 
                    new SelectListItem { Value = "AX", Text = "ÅLAND ISLANDS"}, 
                    new SelectListItem { Value = "AL", Text = "ALBANIA"}, 
                    new SelectListItem { Value = "DZ", Text = "ALGERIA"}, 
                    new SelectListItem { Value = "AS", Text = "AMERICAN SAMOA"}, 
                    new SelectListItem { Value = "AD", Text = "ANDORRA"}, 
                    new SelectListItem { Value = "AO", Text = "ANGOLA"}, 
                    new SelectListItem { Value = "AI", Text = "ANGUILLA"}, 
                    new SelectListItem { Value = "AQ", Text = "ANTARCTICA"}, 
                    new SelectListItem { Value = "AG", Text = "ANTIGUA AND BARBUDA"}, 
                    new SelectListItem { Value = "AR", Text = "ARGENTINA"}, 
                    new SelectListItem { Value = "AM", Text = "ARMENIA"}, 
                    new SelectListItem { Value = "AW", Text = "ARUBA"}, 
                    new SelectListItem { Value = "AU", Text = "AUSTRALIA"}, 
                    new SelectListItem { Value = "AT", Text = "AUSTRIA"}, 
                    new SelectListItem { Value = "AZ", Text = "AZERBAIJAN"}, 
                    new SelectListItem { Value = "BS", Text = "BAHAMAS"}, 
                    new SelectListItem { Value = "BH", Text = "BAHRAIN"}, 
                    new SelectListItem { Value = "BD", Text = "BANGLADESH"}, 
                    new SelectListItem { Value = "BB", Text = "BARBADOS"}, 
                    new SelectListItem { Value = "BY", Text = "BELARUS"}, 
                    new SelectListItem { Value = "BE", Text = "BELGIUM"}, 
                    new SelectListItem { Value = "BZ", Text = "BELIZE"}, 
                    new SelectListItem { Value = "BJ", Text = "BENIN"}, 
                    new SelectListItem { Value = "BM", Text = "BERMUDA"}, 
                    new SelectListItem { Value = "BT", Text = "BHUTAN"}, 
                    new SelectListItem { Value = "BO", Text = "BOLIVIA, PLURINATIONAL STATE OF"}, 
                    new SelectListItem { Value = "BQ", Text = "BONAIRE, SINT EUSTATIUS AND SABA"}, 
                    new SelectListItem { Value = "BA", Text = "BOSNIA AND HERZEGOVINA"}, 
                    new SelectListItem { Value = "BW", Text = "BOTSWANA"}, 
                    new SelectListItem { Value = "BV", Text = "BOUVET ISLAND"}, 
                    new SelectListItem { Value = "BR", Text = "BRAZIL"}, 
                    new SelectListItem { Value = "IO", Text = "BRITISH INDIAN OCEAN TERRITORY"}, 
                    new SelectListItem { Value = "BN", Text = "BRUNEI DARUSSALAM"}, 
                    new SelectListItem { Value = "BG", Text = "BULGARIA"}, 
                    new SelectListItem { Value = "BF", Text = "BURKINA FASO"}, 
                    new SelectListItem { Value = "BI", Text = "BURUNDI"}, 
                    new SelectListItem { Value = "KH", Text = "CAMBODIA"}, 
                    new SelectListItem { Value = "CM", Text = "CAMEROON"}, 
                    new SelectListItem { Value = "CA", Text = "CANADA"}, 
                    new SelectListItem { Value = "CV", Text = "CAPE VERDE"}, 
                    new SelectListItem { Value = "KY", Text = "CAYMAN ISLANDS"}, 
                    new SelectListItem { Value = "CF", Text = "CENTRAL AFRICAN REPUBLIC"}, 
                    new SelectListItem { Value = "TD", Text = "CHAD"}, 
                    new SelectListItem { Value = "CL", Text = "CHILE"}, 
                    new SelectListItem { Value = "CN", Text = "CHINA"}, 
                    new SelectListItem { Value = "CX", Text = "CHRISTMAS ISLAND"}, 
                    new SelectListItem { Value = "CC", Text = "COCOS (KEELING) ISLANDS"}, 
                    new SelectListItem { Value = "CO", Text = "COLOMBIA"}, 
                    new SelectListItem { Value = "KM", Text = "COMOROS"}, 
                    new SelectListItem { Value = "CG", Text = "CONGO"}, 
                    new SelectListItem { Value = "CD", Text = "CONGO, THE DEMOCRATIC REPUBLIC OF THE"}, 
                    new SelectListItem { Value = "CK", Text = "COOK ISLANDS"}, 
                    new SelectListItem { Value = "CR", Text = "COSTA RICA"}, 
                    new SelectListItem { Value = "CI", Text = "CÔTE D'IVOIRE"}, 
                    new SelectListItem { Value = "HR", Text = "CROATIA"}, 
                    new SelectListItem { Value = "CU", Text = "CUBA"}, 
                    new SelectListItem { Value = "CW", Text = "CURAÇAO"}, 
                    new SelectListItem { Value = "CY", Text = "CYPRUS"}, 
                    new SelectListItem { Value = "CZ", Text = "CZECH REPUBLIC"}, 
                    new SelectListItem { Value = "DK", Text = "DENMARK"}, 
                    new SelectListItem { Value = "DJ", Text = "DJIBOUTI"}, 
                    new SelectListItem { Value = "DM", Text = "DOMINICA"}, 
                    new SelectListItem { Value = "DO", Text = "DOMINICAN REPUBLIC"}, 
                    new SelectListItem { Value = "EC", Text = "ECUADOR"}, 
                    new SelectListItem { Value = "EG", Text = "EGYPT"}, 
                    new SelectListItem { Value = "SV", Text = "EL SALVADOR"}, 
                    new SelectListItem { Value = "GQ", Text = "EQUATORIAL GUINEA"}, 
                    new SelectListItem { Value = "ER", Text = "ERITREA"}, 
                    new SelectListItem { Value = "EE", Text = "ESTONIA"}, 
                    new SelectListItem { Value = "ET", Text = "ETHIOPIA"}, 
                    new SelectListItem { Value = "FK", Text = "FALKLAND ISLANDS (MALVINAS)"}, 
                    new SelectListItem { Value = "FO", Text = "FAROE ISLANDS"}, 
                    new SelectListItem { Value = "FJ", Text = "FIJI"}, 
                    new SelectListItem { Value = "FI", Text = "FINLAND"}, 
                    new SelectListItem { Value = "FR", Text = "FRANCE"}, 
                    new SelectListItem { Value = "GF", Text = "FRENCH GUIANA"}, 
                    new SelectListItem { Value = "PF", Text = "FRENCH POLYNESIA"}, 
                    new SelectListItem { Value = "TF", Text = "FRENCH SOUTHERN TERRITORIES"}, 
                    new SelectListItem { Value = "GA", Text = "GABON"}, 
                    new SelectListItem { Value = "GM", Text = "GAMBIA"}, 
                    new SelectListItem { Value = "GE", Text = "GEORGIA"}, 
                    new SelectListItem { Value = "DE", Text = "GERMANY"}, 
                    new SelectListItem { Value = "GH", Text = "GHANA"}, 
                    new SelectListItem { Value = "GI", Text = "GIBRALTAR"}, 
                    new SelectListItem { Value = "GR", Text = "GREECE"}, 
                    new SelectListItem { Value = "GL", Text = "GREENLAND"}, 
                    new SelectListItem { Value = "GD", Text = "GRENADA"}, 
                    new SelectListItem { Value = "GP", Text = "GUADELOUPE"}, 
                    new SelectListItem { Value = "GU", Text = "GUAM"}, 
                    new SelectListItem { Value = "GT", Text = "GUATEMALA"}, 
                    new SelectListItem { Value = "GG", Text = "GUERNSEY"}, 
                    new SelectListItem { Value = "GN", Text = "GUINEA"}, 
                    new SelectListItem { Value = "GW", Text = "GUINEA-BISSAU"}, 
                    new SelectListItem { Value = "GY", Text = "GUYANA"}, 
                    new SelectListItem { Value = "HT", Text = "HAITI"}, 
                    new SelectListItem { Value = "HM", Text = "HEARD ISLAND AND MCDONALD ISLANDS"}, 
                    new SelectListItem { Value = "VA", Text = "HOLY SEE (VATICAN CITY STATE)"}, 
                    new SelectListItem { Value = "HN", Text = "HONDURAS"}, 
                    new SelectListItem { Value = "HK", Text = "HONG KONG"}, 
                    new SelectListItem { Value = "HU", Text = "HUNGARY"}, 
                    new SelectListItem { Value = "IS", Text = "ICELAND"}, 
                    new SelectListItem { Value = "IN", Text = "INDIA"}, 
                    new SelectListItem { Value = "ID", Text = "INDONESIA"}, 
                    new SelectListItem { Value = "IR", Text = "IRAN, ISLAMIC REPUBLIC OF"}, 
                    new SelectListItem { Value = "IQ", Text = "IRAQ"}, 
                    new SelectListItem { Value = "IE", Text = "IRELAND"}, 
                    new SelectListItem { Value = "IM", Text = "ISLE OF MAN"}, 
                    new SelectListItem { Value = "IL", Text = "ISRAEL"}, 
                    new SelectListItem { Value = "IT", Text = "ITALY"}, 
                    new SelectListItem { Value = "JM", Text = "JAMAICA"}, 
                    new SelectListItem { Value = "JP", Text = "JAPAN"}, 
                    new SelectListItem { Value = "JE", Text = "JERSEY"}, 
                    new SelectListItem { Value = "JO", Text = "JORDAN"}, 
                    new SelectListItem { Value = "KZ", Text = "KAZAKHSTAN"}, 
                    new SelectListItem { Value = "KE", Text = "KENYA"}, 
                    new SelectListItem { Value = "KI", Text = "KIRIBATI"}, 
                    new SelectListItem { Value = "KP", Text = "KOREA, DEMOCRATIC PEOPLE'S REPUBLIC OF"}, 
                    new SelectListItem { Value = "KR", Text = "KOREA, REPUBLIC OF"}, 
                    new SelectListItem { Value = "KW", Text = "KUWAIT"}, 
                    new SelectListItem { Value = "KG", Text = "KYRGYZSTAN"}, 
                    new SelectListItem { Value = "LA", Text = "LAO PEOPLE'S DEMOCRATIC REPUBLIC"}, 
                    new SelectListItem { Value = "LV", Text = "LATVIA"}, 
                    new SelectListItem { Value = "LB", Text = "LEBANON"}, 
                    new SelectListItem { Value = "LS", Text = "LESOTHO"}, 
                    new SelectListItem { Value = "LR", Text = "LIBERIA"}, 
                    new SelectListItem { Value = "LY", Text = "LIBYA"}, 
                    new SelectListItem { Value = "LI", Text = "LIECHTENSTEIN"}, 
                    new SelectListItem { Value = "LT", Text = "LITHUANIA"}, 
                    new SelectListItem { Value = "LU", Text = "LUXEMBOURG"}, 
                    new SelectListItem { Value = "MO", Text = "MACAO"}, 
                    new SelectListItem { Value = "MK", Text = "MACEDONIA, THE FORMER YUGOSLAV REPUBLIC OF"}, 
                    new SelectListItem { Value = "MG", Text = "MADAGASCAR"}, 
                    new SelectListItem { Value = "MW", Text = "MALAWI"}, 
                    new SelectListItem { Value = "MY", Text = "MALAYSIA"}, 
                    new SelectListItem { Value = "MV", Text = "MALDIVES"}, 
                    new SelectListItem { Value = "ML", Text = "MALI"}, 
                    new SelectListItem { Value = "MT", Text = "MALTA"}, 
                    new SelectListItem { Value = "MH", Text = "MARSHALL ISLANDS"}, 
                    new SelectListItem { Value = "MQ", Text = "MARTINIQUE"}, 
                    new SelectListItem { Value = "MR", Text = "MAURITANIA"}, 
                    new SelectListItem { Value = "MU", Text = "MAURITIUS"}, 
                    new SelectListItem { Value = "YT", Text = "MAYOTTE"}, 
                    new SelectListItem { Value = "MX", Text = "MEXICO"}, 
                    new SelectListItem { Value = "FM", Text = "MICRONESIA, FEDERATED STATES OF"}, 
                    new SelectListItem { Value = "MD", Text = "MOLDOVA, REPUBLIC OF"}, 
                    new SelectListItem { Value = "MC", Text = "MONACO"}, 
                    new SelectListItem { Value = "MN", Text = "MONGOLIA"}, 
                    new SelectListItem { Value = "ME", Text = "MONTENEGRO"}, 
                    new SelectListItem { Value = "MS", Text = "MONTSERRAT"}, 
                    new SelectListItem { Value = "MA", Text = "MOROCCO"}, 
                    new SelectListItem { Value = "MZ", Text = "MOZAMBIQUE"}, 
                    new SelectListItem { Value = "MM", Text = "MYANMAR"}, 
                    new SelectListItem { Value = "NA", Text = "NAMIBIA"}, 
                    new SelectListItem { Value = "NR", Text = "NAURU"}, 
                    new SelectListItem { Value = "NP", Text = "NEPAL"}, 
                    new SelectListItem { Value = "NL", Text = "NETHERLANDS"}, 
                    new SelectListItem { Value = "NC", Text = "NEW CALEDONIA"}, 
                    new SelectListItem { Value = "NZ", Text = "NEW ZEALAND"}, 
                    new SelectListItem { Value = "NI", Text = "NICARAGUA"}, 
                    new SelectListItem { Value = "NE", Text = "NIGER"}, 
                    new SelectListItem { Value = "NG", Text = "NIGERIA"}, 
                    new SelectListItem { Value = "NU", Text = "NIUE"}, 
                    new SelectListItem { Value = "NF", Text = "NORFOLK ISLAND"}, 
                    new SelectListItem { Value = "MP", Text = "NORTHERN MARIANA ISLANDS"}, 
                    new SelectListItem { Value = "NO", Text = "NORWAY"}, 
                    new SelectListItem { Value = "OM", Text = "OMAN"}, 
                    new SelectListItem { Value = "PK", Text = "PAKISTAN"}, 
                    new SelectListItem { Value = "PW", Text = "PALAU"}, 
                    new SelectListItem { Value = "PS", Text = "PALESTINIAN TERRITORY, OCCUPIED"}, 
                    new SelectListItem { Value = "PA", Text = "PANAMA"}, 
                    new SelectListItem { Value = "PG", Text = "PAPUA NEW GUINEA"}, 
                    new SelectListItem { Value = "PY", Text = "PARAGUAY"}, 
                    new SelectListItem { Value = "PE", Text = "PERU"}, 
                    new SelectListItem { Value = "PH", Text = "PHILIPPINES"}, 
                    new SelectListItem { Value = "PN", Text = "PITCAIRN"}, 
                    new SelectListItem { Value = "PL", Text = "POLAND"}, 
                    new SelectListItem { Value = "PT", Text = "PORTUGAL"}, 
                    new SelectListItem { Value = "PR", Text = "PUERTO RICO"}, 
                    new SelectListItem { Value = "QA", Text = "QATAR"}, 
                    new SelectListItem { Value = "RE", Text = "RÉUNION"}, 
                    new SelectListItem { Value = "RO", Text = "ROMANIA"}, 
                    new SelectListItem { Value = "RU", Text = "RUSSIAN FEDERATION"}, 
                    new SelectListItem { Value = "RW", Text = "RWANDA"}, 
                    new SelectListItem { Value = "BL", Text = "SAINT BARTHÉLEMY"}, 
                    new SelectListItem { Value = "SH", Text = "SAINT HELENA, ASCENSION AND TRISTAN DA CUNHA"}, 
                    new SelectListItem { Value = "KN", Text = "SAINT KITTS AND NEVIS"}, 
                    new SelectListItem { Value = "LC", Text = "SAINT LUCIA"}, 
                    new SelectListItem { Value = "MF", Text = "SAINT MARTIN (FRENCH PART)"}, 
                    new SelectListItem { Value = "PM", Text = "SAINT PIERRE AND MIQUELON"}, 
                    new SelectListItem { Value = "VC", Text = "SAINT VINCENT AND THE GRENADINES"}, 
                    new SelectListItem { Value = "WS", Text = "SAMOA"}, 
                    new SelectListItem { Value = "SM", Text = "SAN MARINO"}, 
                    new SelectListItem { Value = "ST", Text = "SAO TOME AND PRINCIPE"}, 
                    new SelectListItem { Value = "SA", Text = "SAUDI ARABIA"}, 
                    new SelectListItem { Value = "SN", Text = "SENEGAL"}, 
                    new SelectListItem { Value = "RS", Text = "SERBIA"}, 
                    new SelectListItem { Value = "SC", Text = "SEYCHELLES"}, 
                    new SelectListItem { Value = "SL", Text = "SIERRA LEONE"}, 
                    new SelectListItem { Value = "SG", Text = "SINGAPORE"}, 
                    new SelectListItem { Value = "SX", Text = "SINT MAARTEN (DUTCH PART)"}, 
                    new SelectListItem { Value = "SK", Text = "SLOVAKIA"}, 
                    new SelectListItem { Value = "SI", Text = "SLOVENIA"}, 
                    new SelectListItem { Value = "SB", Text = "SOLOMON ISLANDS"}, 
                    new SelectListItem { Value = "SO", Text = "SOMALIA"}, 
                    new SelectListItem { Value = "ZA", Text = "SOUTH AFRICA"}, 
                    new SelectListItem { Value = "GS", Text = "SOUTH GEORGIA AND THE SOUTH SANDWICH ISLANDS"}, 
                    new SelectListItem { Value = "SS", Text = "SOUTH SUDAN"}, 
                    new SelectListItem { Value = "ES", Text = "SPAIN"}, 
                    new SelectListItem { Value = "LK", Text = "SRI LANKA"}, 
                    new SelectListItem { Value = "SD", Text = "SUDAN"}, 
                    new SelectListItem { Value = "SR", Text = "SURINAME"}, 
                    new SelectListItem { Value = "SJ", Text = "SVALBARD AND JAN MAYEN"}, 
                    new SelectListItem { Value = "SZ", Text = "SWAZILAND"}, 
                    new SelectListItem { Value = "SE", Text = "SWEDEN"}, 
                    new SelectListItem { Value = "CH", Text = "SWITZERLAND"}, 
                    new SelectListItem { Value = "SY", Text = "SYRIAN ARAB REPUBLIC"}, 
                    new SelectListItem { Value = "TW", Text = "TAIWAN, PROVINCE OF CHINA"}, 
                    new SelectListItem { Value = "TJ", Text = "TAJIKISTAN"}, 
                    new SelectListItem { Value = "TZ", Text = "TANZANIA, UNITED REPUBLIC OF"}, 
                    new SelectListItem { Value = "TH", Text = "THAILAND"}, 
                    new SelectListItem { Value = "TL", Text = "TIMOR-LESTE"}, 
                    new SelectListItem { Value = "TG", Text = "TOGO"}, 
                    new SelectListItem { Value = "TK", Text = "TOKELAU"}, 
                    new SelectListItem { Value = "TO", Text = "TONGA"}, 
                    new SelectListItem { Value = "TT", Text = "TRINIDAD AND TOBAGO"}, 
                    new SelectListItem { Value = "TN", Text = "TUNISIA"}, 
                    new SelectListItem { Value = "TR", Text = "TURKEY"}, 
                    new SelectListItem { Value = "TM", Text = "TURKMENISTAN"}, 
                    new SelectListItem { Value = "TC", Text = "TURKS AND CAICOS ISLANDS"}, 
                    new SelectListItem { Value = "TV", Text = "TUVALU"}, 
                    new SelectListItem { Value = "UG", Text = "UGANDA"}, 
                    new SelectListItem { Value = "UA", Text = "UKRAINE"}, 
                    new SelectListItem { Value = "AE", Text = "UNITED ARAB EMIRATES"}, 
                    new SelectListItem { Value = "GB", Text = "UNITED KINGDOM"}, 
                    new SelectListItem { Value = "US", Text = "UNITED STATES"}, 
                    new SelectListItem { Value = "UM", Text = "UNITED STATES MINOR OUTLYING ISLANDS"}, 
                    new SelectListItem { Value = "UY", Text = "URUGUAY"}, 
                    new SelectListItem { Value = "UZ", Text = "UZBEKISTAN"}, 
                    new SelectListItem { Value = "VU", Text = "VANUATU"}, 
                    new SelectListItem { Value = "VE", Text = "VENEZUELA, BOLIVARIAN REPUBLIC OF"}, 
                    new SelectListItem { Value = "VN", Text = "VIET NAM"}, 
                    new SelectListItem { Value = "VG", Text = "VIRGIN ISLANDS, BRITISH"}, 
                    new SelectListItem { Value = "VI", Text = "VIRGIN ISLANDS, U.S."}, 
                    new SelectListItem { Value = "WF", Text = "WALLIS AND FUTUNA"}, 
                    new SelectListItem { Value = "EH", Text = "WESTERN SAHARA"}, 
                    new SelectListItem { Value = "YE", Text = "YEMEN"}, 
                    new SelectListItem { Value = "ZM", Text = "ZAMBIA"}, 
                    new SelectListItem { Value = "ZW", Text = "ZIMBABWE"}, 

                };

Answer 3

答案在这里：ASP.Net Html.DropDownList Selected Element not Selected也可能是解决方案。

您可以使用“Countries”作为下拉列表的名称，使用“countries”作为SelectList的名称。尝试将其中一个重命名为不同的东西。

Answer 4

我知道这篇文章很老，但对于那些寻找国家名单的人来说，这是一个简单的方法：

// List of coutries
List<string> CountryList = new List<string>();

CultureInfo[] CInfoList = CultureInfo.GetCultures(CultureTypes.SpecificCultures);

CountryList.Add("");
foreach (CultureInfo CInfo in CInfoList)
{
    RegionInfo R = new RegionInfo(CInfo.LCID);
    if (!(CountryList.Contains(R.EnglishName)))
    {
        CountryList.Add(R.EnglishName);
    }
}
CountryList.Sort();