ASP.NET MVC - Creating a DropDownList helper for enums

re: ASP.NET MVC - Creating a DropDownList helper for enums

Shimmy Weitzhandler — Wed, 24 Apr 2013 23:57:50 GMT

What about flags Enum??

re: ASP.NET MVC - Creating a DropDownList helper for enums

Jeremy Holovacs — Tue, 19 Mar 2013 20:55:34 GMT

for the nullable enum,

ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData)

fails before getting to the type line.

re: ASP.NET MVC - Creating a DropDownList helper for enums

firepol — Wed, 20 Feb 2013 05:36:21 GMT

Hi Stuart, thank you for the great tutorial! I tried Shea Strickland suggestion but it didn't work for me (I wanted to save the integer in my DB). So I kept the Helper as explained in the tutorial and did as suggested here in my model class: stackoverflow.com/.../best-method-to-store-enum-in-database hope it helps, I lost a few hours to figure this out...

re: ASP.NET MVC - Creating a DropDownList helper for enums

Daniel Bradley — Thu, 21 Jun 2012 11:53:19 GMT

Did my own implementation, created a new gist for people to fork:

gist.github.com/2965119

Summary:

Generic expression support

Nullable<Enum> support

Optional custom display text

Full documentation

re: ASP.NET MVC - Creating a DropDownList helper for enums

Fernando Alonso — Sat, 14 Apr 2012 03:06:52 GMT

I liked this post. Thanks Stuart.

I made some changes in order to use DisplayAttribute annotations instead of a TypeConverter. I like to define my enums this way:

public enum TransferFrequency

{

[Display(Name = "One time, immediately")]

OneTime,

[Display(Name = "One time, on...")]

OneTimeOn,

[Display(Name = "Weekly")]

Weekly

}

Here's the code in case anyone is interested (semi tested so use at your own risk):

public static MvcHtmlString EnumDropDownListFor<TModel, TEnum>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TEnum>> expression, object htmlAttributes)

{

ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);

Type enumType = GetNonNullableModelType(metadata);

Type baseEnumType = Enum.GetUnderlyingType(enumType);

List<SelectListItem> items = new List<SelectListItem>();

foreach (FieldInfo field in enumType.GetFields(BindingFlags.Static | BindingFlags.GetField | BindingFlags.Public))

{

string text = field.Name;

string value = Convert.ChangeType(field.GetValue(null), baseEnumType).ToString();

bool selected = field.GetValue(null).Equals(metadata.Model);

foreach (var displayAttribute in field.GetCustomAttributes(true).OfType<DisplayAttribute>())

{

text = displayAttribute.GetName();

}

items.Add(new SelectListItem()

{

Text = text,

Value = value,

Selected = selected

});

}

if (metadata.IsNullableValueType)

{

items.Insert(0, new SelectListItem { Text = "", Value = "" });

}

return SelectExtensions.DropDownListFor(htmlHelper, expression, items, htmlAttributes);

}

re: ASP.NET MVC - Creating a DropDownList helper for enums

Nick — Fri, 16 Mar 2012 17:00:28 GMT

I took a stab at a different approach for the SplitString method. Not exhaustively tested though:

public string SplitString(string stringValue)

{

return Regex.Replace(stringValue, @"((?<=[a-z])[A-Z]\w|(?<=\w)[A-Z][a-z])", @" $0");

}

re: ASP.NET MVC - Creating a DropDownList helper for enums

stuartle — Fri, 17 Jun 2011 08:05:18 GMT

@ Damo123 - the code I used for the blog post is below. I've not tested it beyond the needs of this blog post though, so use with extreme caution :-)

public class PascalCaseWordSplittingEnumConverter : EnumConverter

{

public PascalCaseWordSplittingEnumConverter(Type type)

: base(type)

{

}

public override object ConvertTo(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value, Type destinationType)

{

if (destinationType == typeof(string))

{

string stringValue = (string) base.ConvertTo(context, culture, value, destinationType);

stringValue = SplitString(stringValue);

return stringValue;

}

return base.ConvertTo(context, culture, value, destinationType);

}

public string SplitString(string stringValue)

{

StringBuilder buf = new StringBuilder(stringValue);

// assume first letter is upper!

bool lastWasUpper = true;

int lastSpaceIndex = -1;

for (int i = 1; i < buf.Length; i++)

{

bool isUpper = char.IsUpper(buf[i]);

if (isUpper & !lastWasUpper)

{

buf.Insert(i, ' ');

lastSpaceIndex = i;

}

if (!isUpper && lastWasUpper)

{

if (lastSpaceIndex != i - 2)

{

buf.Insert(i - 1, ' ');

lastSpaceIndex = i - 1;

}

lastWasUpper = isUpper;

}

return buf.ToString();

}

re: ASP.NET MVC - Creating a DropDownList helper for enums

Damo123 — Thu, 16 Jun 2011 01:23:41 GMT

Great post Stuart. Thanks very much.

How about posting the code for PascalCaseWordSplittingEnumConverter? I've had a look at creating a custom type converter and it seems non-trivial.

cheers.

re: ASP.NET MVC - Creating a DropDownList helper for enums

Shea Strickland — Thu, 10 Feb 2011 13:07:39 GMT

In addition to what stuartle said for converting to the enum's actual value, not name, you can use:

Type baseEnumType = Enum.GetUnderlyingType(enumType);

...

then set the value of the SelectListItem to:

Value = Convert.ChangeType(value, baseEnumType).ToString(),

...

For those instances where you don't actually know if the underlying type of you Enum is Int :)

re: ASP.NET MVC - Creating a DropDownList helper for enums

Mounhim — Tue, 08 Feb 2011 15:00:45 GMT

Done compiling. I'll read the next time better before commenting. Sorry.