Question

Is it possible to specify an object as a parameter in MVC with default values in some way?

E.g.

    public virtual ViewResult Index(RequirementFilters requirementFilters)

I’d like to initialize the values of a couple of parameters on RequirementFilters?

At the moment I am doing

public virtual ViewResult Index(int status=1, bool required =false)

I wanted to create a Filter Object so I could re-use it but I can’t figure out way of setting defaults for the object in the Action Parameters.

Thanks

Graeme

Answer 1

You could create a custom ActionFilter attribute and create an instance of your Filter Object there. You can provide some properties through the custom attribute.

Here’s an example:

public class DefaultQuerySettingsAttribute : ActionFilterAttribute
{
        public string ParameterName { get; set; }
        public Type SettingsType { get; set; }
        public int Rows { get; set; }
        public string SortColumn { get; set; }
        public string SortOrder { get; set; }
        public bool PagingEnabled { get; set; }

        public DefaultQuerySettingsAttribute()
        {
            this.ParameterName = "settings";

            var defaultSettings = new QuerySettings();
            this.Rows = defaultSettings.Rows;
            this.SortColumn = defaultSettings.SortColumn;
            this.SortOrder = defaultSettings.SortOrder;
            this.PagingEnabled = defaultSettings.PagingEnabled;
        }

        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            base.OnActionExecuting(filterContext);

            if (filterContext.ActionParameters.ContainsKey(this.ParameterName))
            {
                var querySettings = filterContext.ActionParameters[this.ParameterName] as QuerySettings;

              if (querySettings == null || string.IsNullOrWhiteSpace(querySettings.SortColumn))
                                        filterContext.ActionParameters[this.ParameterName] = this.GetQuerySettings();
            }
       }

        private QuerySettings GetQuerySettings()
        {
            var querySettings = (QuerySettings)Activator.CreateInstance(SettingsType ?? typeof(QuerySettings));
            querySettings.Rows = Rows;
            querySettings.SortColumn = SortColumn;
            querySettings.SortOrder = SortOrder;
            querySettings.PagingEnabled = PagingEnabled;

            return querySettings;
        }
   }

ParameterName is the name of the argument in the action method (requirementFilters in your case).
You can also specify actual type that will be instantiated by providing SettingsType.