Pass collection of enums to ASP.NET MVC ActionMethod

Question

Is there a way to pass a collection of Enums to an ActionMethod (on a GET) automatically?

For example, if I have the following enum definition:

enum DaysEnum {Sat, Sun, Mon, Tue, Wed, Thu, Fri};

and, I have an ActionMethod definition of:

ActionResult SampleActionMethod ( List<DaysEnum> days)

Is there a way I could render, in a View, a URL that would pass in a collection of DayEnums. Something like:

var someDays = new List<DaysEnum> {DaysEnum.Sat, DaysEnum.Sun, DaysEnum.Mon};

Url.Route(new { days = someDays, controller="whatever", action="SampleActionMethod"});

The default model binder doesn't seem to support this, since I'm currently getting the following rendered:

http://.../System.Collections.Generic.List`1[DaysEnum]

I know I can do this by manually flattening the collection to, say, a dash-deliniated string, and then recreate the collection in the ActionMethod, but I was looking at something more elegant. Various blog posts talk about passing in collections, but that is more about when doing POSTS.

Answer 1

<%= Html.ActionLink("test enums", "SampleActionMethod", new RouteValueDictionary { 
    { "days[0]", DaysEnum.Sun }, { "days[1]", DaysEnum.Mon } 
}) %>

Answer 2

i m afraid complex data types can not be carried with GET request. u can use some hidden values and post the data if u do want to send these values as collection

Answer 3

We do this using a custom model binder for the controller parameter, and an extension method to form the parameter in the URL.

The model binder looks like this:

/// <summary>
/// Custom binder class.
/// </summary>
public class DaysEnumModelBinder : IModelBinder
{
    /// <summary>
    /// Convert a comma-separated string to a list.
    /// </summary>
    /// <param name="rawValue">Raw value from binding context.</param>
    /// <returns>List of enum values.</returns>
    public static List<DaysEnum> ConvertArray(object rawValue)
    {
        var results = new List<DaysEnum>();

        string[] query = rawValue as string[];

        if (query != null && query.Length != 0)
        {
            string[] parts = query[0].Split(',');

            foreach (string part in parts)
            {
                try
                {
                    DaysEnum resultValue = (DaysEnum)Enum.Parse(typeof(DaysEnum), part, true);
                    results.Add(resultValue);
                }
                catch (ArgumentException)
                {
                }
            }
        }

        return results;
    }

    /// <summary>
    /// Implement IModelBinder to bind a comma-separated array of int values to a single array.
    /// </summary>
    /// <param name="controllerContext">The controller context.</param>
    /// <param name="bindingContext">The binding context.</param>
    /// <returns>Int array where applied to the correct type of object.</returns>
    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        if (!bindingContext.ValueProvider.ContainsPrefix(bindingContext.ModelName))
        {
            return new DefaultModelBinder().BindModel(controllerContext, bindingContext);
        }

        if (bindingContext.ModelType == typeof(DaysEnum[]))
        {
            List<DaysEnum> results = ConvertArray(bindingContext.ValueProvider.GetValue(bindingContext.ModelName).RawValue);

            return results.ToArray();
        }

        return new DefaultModelBinder().BindModel(controllerContext, bindingContext);
    }
}

Then in your controller method you hook up the binder like so:

ActionResult MyMethod([ModelBinder(typeof(DaysEnumModelBinder))] DaysEnum[] days)
{
    ...
}

Finally in your view render the URL with something like string.Join(",", days.Select(d => d.ToString())).