Want to save selected (i.e., more than 1) enums as string with NHibernate

Question

I cannot for the life of me get this to work with my existing code, but I am trying to save my enum selections as strings in NHibernate. Basically, I have a UI check box and if the user selects multiple check boxes I want to store those selections. Now, I can get NHibernate to store ONE selection (e.g., from a drop down or radio button list, where the user is limited to one choice only).

This is the jist of what I have for an enum:

public enum IncomeType
{
    [Display(Name = "Full-Time Employment")]
    FullTime,
    [Display(Name = "Part-Time Employment")]
    PartTime,
    [Display(Name = "Self-Employment")]
    SelfEmployed,
    [Display(Name = "Rental")]
    Rental,
    [Display(Name = "Social Security Payments")]
    SocialSecurity,
    [Display(Name = "Retirement / Pension Payments")]
    Retirement,
    [Display(Name = "Child Support Payments")]
    ChildSupport,
    [Display(Name = "Spousal Maintenance")]
    Maintenance,
    [Display(Name = "Other")]
    Other
}

I use a method to "select" whether a checkbox list is shown (if my BulkItemThreshold equals the number of options, a checkbox list is displayed). Here is that method:

public static IEnumerable<SelectListItem> GetItemsFromEnumString<T>
    (T selectedValue = default(T)) where T : struct
{
    return from name in Enum.GetNames(typeof(T))
       let enumValue = Convert.ToString((T)Enum.Parse(typeof(T), name, true))
    
    select new SelectListItem
    {
        Text = GetEnumDescription(name, typeof(T)),
        Value = enumValue,
        Selected = enumValue.Equals(selectedValue)
    };
}

(Note: some items in there are helpers, but I don't believe they are relevant; also, the selected input is displayed using a template .cshtml file - again, not sure if that's relevant)

Now, I call this thusly:

public class IncomeTypeSelectorAttribute : SelectorAttribute
{
    public override IEnumerable<SelectListItem> GetItems()
    {
        return Selector.GetItemsFromEnumString<IncomeType>();
    }
}

And finally, we get to the virtual property (using a proxy) but this is where NHibernate throws a wrench (Note: this was working fine for me before NHibernate, and now I am trying to get many lines of code working with it WITHOUT having to re-do everything; if I re-do everything I will probably triple the code I already have to get it to work):

Property (record):

[IncomeTypeSelector(BulkSelectionThreshold = 9)]
public virtual List<string> IndividualIncomeTypeCheckBox { get; set; }

proxy (part):

public List<string> IndividualIncomeTypeCheckBox
{
    get { return Record.IndividualIncomeTypeCheckBox; }
    set { Record.IndividualIncomeTypeCheckBox = value; }
}

Again, this is how I was doing things and it was working great before NHibernate. But now I have to use NHibernate. No getting around it.

I am using a service class that it tying the two together in a Create method to save in the DB with NHibernate, and for the above it would ordinarily look like this:

 part.IndividualIncomeTypeCheckBox = record.IndividualIncomeTypeCheckBox;

This would work if it were just one selection.

Well, I've spent a good two (2) months trying to get this to work. It's tough because I have lots of code where the user can make only one selection (such as with a radiobutton list) and it works GREAT - even with NHibernate. Let me give you an example:

public virtual IncomeType? IndividualIncomeTypeCheckBox { get; set; }

If I do the above, it will display a drop down list, and NHibernate will store the ONE allowable option selected by the user in the DB no problem. But more than one option with List<string> does not work.

Now, I have tried everything I could find here or elsewhere and nothing works. Yes, I know it should be IList<IncomeType> or some other variant. But if I use this then NHibernate requires that IncomeType be another table in the DB. This is too much code to write for such a simple thing I believe. We are not talking a many-to-many relation in the sense that this is not a User with Multiple addresses (wherein addresses would have street, city, state, zip, etc.).

I have tried different types of proxy get and set code, but nothing works. I have tried [Flags] and other things working with string only, but to no avail. Those last solutions would "work" but ONLY to save the first item selected out of multiple (i.e., in my scenario, if the user selected "FullTime" and "Rental" as Income Types, then only "FullTime" (string) would be saved or "1" ([Flags]/int), not both items selected.

I have a situation where I re-display the choices using a ReadOnly attribute like this:

[IncomeTypeSelector]
[ReadOnly(true)]
public List<string> IndividualIncomeTypeCheckBoxPost
{
    get { return IndividualIncomeTypeCheckBox; }
}

This would display on the UI, but I tried doing something like this with NHibernate and it wouldn't work.

Could anyone please show me, using the above, how I can go about getting NHibernate to store more than one enum in this checkbox list scenario?

UPDATE: More poking around here and on the web, and I came up with the following (which still does not work).

Property (record):

[IncomeTypeSelector(BulkSelectionThreshold = 9)]
public virtual IList<IncomeTypeRecord> IndividualIncomeTypeCheckBox
{ 
    get { return incomeType; } 
    set { incomeType= value; } 
}
private IList<IncomeTypeRecord> incomeType = 
    new List<IncomeTypeRecord>();

Proxy (part):

public IList<IncomeTypeRecord> IndividualIncomeTypeCheckBox
{
    get { return Record.IndividualIncomeTypeCheckBox; }
    set { Record.IndividualIncomeTypeCheckBox= value; }
}

And a change to the enum:

public enum IncomeType : int // removing int & value still gives validate error
{
[Display(Name = "Full-Time Employment")]
FullTime = 1,
[Display(Name = "Part-Time Employment")]
PartTime,
....
}

And I added this class to support IncomeTypeRecord

public class IncomeTypeRecord
{
    public virtual int Id { get; set; }
    public virtual IncomeType Value { get; set; }
}

HOWEVER, when I get to the UI screen and pick one or more options I get a validation error (value not valid). For example, say I pick FullTime alone, or pick FullTime and Retirement, then the UI will display the following error:

The value 'FullTime' is invalid.

The value 'FullTime,Retirement' is invalid.

(respectively)

Even if I remove the int declaration for the enum and get rid of the value I started with "1", I still get this validation error. I tried messing around with and adding different model binders (which now has me stumped as to whether my original problem still exists and now I have a different problem - but you still get bounty points :) ).

Pulling my hair out. If I could offer more bounty I would. I need a definitive solution. I appreciate any help.

UPDATE This is what I have so far:

Record:

public virtual string IndividualIncomeTypeCheckBox{ get; set; }

Part:

//If I do IEnumberable<string> my .Select throws a cast error
public IEnumerable<IncomeType> IndividualIncomeTypeCheckBox
    {
        get
        {
            return Record
                .IndividualIncomeTypeCheckBox
                .Split(',')
                .Select(r => (IncomeType)Enum.Parse(typeof(IncomeType), r));
        }
        set { Record.IndividualIncomeTypeCheckBox= value 
            == null ? null : String.Join(",", value); }
    }

Service Class:

public SimplePart CreateSimple(SimplePartRecord record)
{
    SimplePart simple = Services.ContentManager.Create<SimplePart>("Simple");
    ...
    //How I would save a FirstName property (example Part / PartRecord below)
    //public virtual string FirstName { get; set; } - PartRecord
    //public string FirstName - Part
    //{
    //    get { return Record.FirstName ; }
    //    set { Record.FirstName= value; }
    //}
    simple.FirstName = record.FristName;
    ...
    //I obviously cannot do the following with the above IncomeType
    //Getting cannot convert string to IEnumerable error
    //How would I write this:
    simple.IndividualIncomeTypeCheckBox = record.IndividualIncomeTypeCheckBox;
    ...
}

And this is how it's called in a controller (this persists to DB): (Updating Controller code)

public ActionResult Confirm(string backButton, string nextButton)
{
    if (backButton != null)
        return RedirectToAction("WrapUp");
    else if ((nextButton != null) && ModelState.IsValid)
    {
        _myService.CreateSimple(myData.SimplePartRecord);
        return RedirectToAction("Submitted");
    }
    else
        return View(myData);
}

Updating with additional code (serialization and view model):

"myData" is defined in the controller (using Serialization) as:

private MyViewModel myData;
protected override void OnActionExecuting(ActionExecutingContext filterContext)
{
    var serialized = Request.Form["myData"];
    if (serialized != null)
    {
        myData = (MyViewModel)new MvcSerializer().Deserialize
            (serialized, SerializationMode.Signed);
        TryUpdateModel(myData);
    }
    else
        myData = (MyViewModel)TempData["myData"] ?? new MyViewModel();
    TempData.Keep();
}
protected override void OnResultExecuted(ResultExecutedContext filterContext)
{
   if (filterContext.Result is RedirectToRouteResult)
        TempData["myData"] = myData;
}

I use Serialization because I set up a multi-step wizard (as seen in the controller action "backButton" "nextButton) on the front-end. I am not using a driver (which can only display Admin or on the front-end but then only on .cshtml files directly under the ~/Views folder (not in a structured folder list like I am using)). No driver = no update view model type code = no mechanism to "create" the data in the DB. If I do not use some "create" type method, the form will submit but all the data will be "NULL".

When you say that the data should be persisted automatically, I am sorry but I do not see how. All the stuff I read or code I review has SOME method of updating the DB with whatever is entered in a form. If I am missing something, my apologies.

"MyViewModel" is pretty straightforward:

[Serializabel]
public class MyViewModel
{
    public SimplePartRecord SimplePartRecord { get; set; }
}

And, just in case, here is the relevant portion of the migration (return 1 is a completely separate and unrelated table):

public int UpdateFrom1()
{
SchemaBuilder.CreateTable("SimplePartRecord",
    table => table
    .ContentPartRecord()
        ...
        .Column("IndividualIncomeTypeCheckBox", DbType.String)
        ...
    );
ContentDefinitionManager.AlterPartDefinition("SimplePart",
    part => part
    .Attachable(false));
return 2;
}

The error I am getting is

Cannot implicitly convert type 'string' to 'System.Collections.Generic.IEnumerable'"

when I do the following in the "Create" method of my service class:

simple.IndividualIncomeTypeCheckBox = record.IndividualIncomeTypeCheckBox;

One additional thought: I tried using the n-n Relation sample to handle this scenario. Aside from it being a lot of extra code for what I thought should be straightforward and simple, because of the way I am using Serialization I had a lot of object reference errors and could not figure out how to properly code my controller to handle it.

Colubrine

Is it a requirement to persist your enum as a string in the database? Or if you could get a [Flags] enum to work would that be feasible? – Electrothermics

Answer 1

The problem is simply that it won't be able to map a List without building a full relationship with an intermediate association table. It is way simpler to have the record store the values as a comma-separated string (so your record property is a string, not a list of string) and your part can map back and forth between string and List.

You can find an example of something very close here:

https://bitbucket.org/bleroy/nwazet.commerce/src/d722cbebea525203b22c445905c9f28d2af7db46/Models/ProductAttributesPartRecord.cs?at=default

https://bitbucket.org/bleroy/nwazet.commerce/src/d722cbebea525203b22c445905c9f28d2af7db46/Models/ProductAttributesPart.cs?at=default

It's not using enum values, instead it's a list of ids, but that should give you a good idea about how to make this work fairly simply: parsing enums you already know how to do.

Let me know if you need more details, but I think that's what you needed to get unblocked.

Stentor

Thanks for bearing with me. I started out using the suggestion you made regarding the DiscountPart.cs, and then later the suggestion in my Service class to do part.MyProperty = new[] {"foo", "bar"};. The ProductAttributesPart.cs seems to be along the same lines. I just cannot figure out how to code it as it relates to the enum. Given the code I supplied, could I impose for a concrete example? Specifically (this isn't in my question), how would I code my Service class which is "creating" the entries in the DB (the part.MyProperty that I mentioned)? – Colubrine

As long as you have a proper handler setting up the repository, and your migration is properly written, you don't have anything more to do to ensure persistence, so I'm not sure specifically what the remaining issue is. To parse the stored string into the list of enum values, I would just, in the part's property getter, do something like string.Split(new[] ',', Record.IncomeTypes).Select(s => (IncomeType)Enum.Parse(typeof(IncomeType), s)) – Stentor

I am not using a driver (so I have no other mechanism to save the input in the DB, as far as I know; I tried running the site without that service class and although my form submitted the data saved was simply "NULL"). These inputs are on the front-end not in the admin. I have a service class that has a "Create" method, wherein I go through all of my fields (part.MyProperty = record.MyProperty), which I then call in my Controller. So I cannot get the code right in this instance for part.MyProperty = ??? in order to persist in the DB for this particular scenario. – Colubrine

I don't understand that part about copying the property from the record to the part. That doesn't seem to make a lot of sense: the part property is usually a proxy for the record property. So do you now have a string property on your record? If so, is the remaining problem with model binding? – Stentor

From what I seen in some modules, a "Create" method is done in a service class and then, for example, called in a Controller to persist data. From what I see in more complicated modules is this is done in a driver with an "Update" or "Edit" method, for example. I'm going to update my question to show what I am doing, and now where I am stuck. Thanks for being patient with me. – Colubrine

Still doesn't make sense. You seem to have no parameters to your controller action (whereas there should be some model binding going on there), and you've omitted the code that might have set things right. Then, you pass a record into your service whose origin seems really mysterious, and then in that service you copy the properties of the mystery record onto the part, which itself has its own record. Also, you have not explained how this fails. – Stentor

What should be done is that you should have something like a string[] parameter to your action, and then pass that into your service method. The service method should then set the part property, and never touch a record. – Stentor

1. There is no reason to have a filter in there. 2. Your view model is not simple. There is no reason to have a record on there. Something like a string[] would be easier and could just be an action parameter. 3. Please show your view code. – Stentor

Answer 2

There's a lot of info to wade through here so hopefully I haven't missed the point. It appears to me that the goals are:

• The business class has a collection property of IList<IncomeType> without requiring an additional table
• The values in that collection should be persisted as a delimited string of the enum names

The best approach is to use a custom user type (an implementation of NHibernate.UserTypes.IUserType) to map the property. Below is a generic IUserType that will map an enum of type T from an IList<T> property to a comma delimited string in the database and back again. There's no easy way to restrict T to an enum but the code will only work with enums.

Mapping a property using the custom type is simple with Fluent NHibernate:

public class Person
{
    public Person()
    {
        IncomeTypes = new List<IncomeType>();
    }

    public virtual int PersonId { get; protected set; }
    public virtual string FirstName { get; set; }
    public virtual string LastName { get; set; }

    public virtual IList<IncomeType> IncomeTypes { get; protected set; }
}

public class PersonMap : ClassMap<Person>
{
    public PersonMap()
    {
        Table("Person");
        Id(x => x.PersonId).GeneratedBy.Identity();
        Map(x => x.FirstName);
        Map(x => x.LastName);
        Map(x => x.IncomeTypes).CustomType<EnumAsDelimitedStringType<IncomeType>>();
    }
}

And here's the code for the user type:

public class EnumAsDelimitedStringType<T> : IUserType
{
    public new bool Equals(object x, object y)
    {
        if (ReferenceEquals(x, y))
        {
            return true;
        }
        var xList = x as IList<T>;
        var yList = y as IList<T>;
        if (xList == null || yList == null)
        {
            return false;
        }
        // compare set contents
        return xList.OrderBy(xValue => xValue).SequenceEqual(yList.OrderBy(yValue => yValue));
    }

    public int GetHashCode(object x)
    {
        return x.GetHashCode();
    }

    public object NullSafeGet(IDataReader rs, string[] names, object owner)
    {
        var outValue = NHibernateUtil.AnsiString.NullSafeGet(rs, names[0]) as string;
        if (string.IsNullOrEmpty(outValue))
        {
            return new List<T>();
        }
        var getValueArray = outValue.Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries);
        return Array.ConvertAll(getValueArray, s => (T)Enum.Parse(typeof(T), s)).ToList();
    }

    public void NullSafeSet(IDbCommand cmd, object value, int index)
    {
        var inValue = value as IList<T>;
        // set to string.Empty if you prefer to store that instead of null when the collection is null or empty
        object setValue = null;
        if (inValue != null && inValue.Any())
        {
            var setValueArray = Array.ConvertAll(inValue.ToArray(), v => Enum.GetName(typeof(T), v));
            setValue = string.Join(",", setValueArray);
        }
        NHibernateUtil.AnsiString.NullSafeSet(cmd, setValue, index);
    }

    public object DeepCopy(object value)
    {
        return value;
    }

    public object Replace(object original, object target, object owner)
    {
        return original;
    }

    public object Assemble(object cached, object owner)
    {
        return cached;
    }

    public object Disassemble(object value)
    {
        return value;
    }

    public SqlType[] SqlTypes
    {
        get { return new[] {new SqlType(DbType.AnsiString)}; }
    }
    public Type ReturnedType
    {
        get { return typeof(IList<T>); }
    }

    public bool IsMutable
    {
        get { return false; }
    }
}

Magog

+1 for IUserType to use Fluent nHibernate mapping. Worth also checking .Access fluent mapping option: https://mcmap.net/q/1189344/-mapping-a-list-lt-string-gt-to-a-delimited-string-with-fluent-nhibernate – Sams

Very elegant solution. But... this does not seem to work when querying on the custom mapped property. ` private void QueryTest(NHibernate.ISession session) { var cbs = session.Query<Foo>(); var filtered = cbs.Where(x => x.Bars.Any(r => r == "1")); try { var filteredList = filtered.ToList(); } catch (Exception ex) { Console.Write(ex); } } ` throws: Exception occurred getter of Foo.Id Inner Exception: Object does not match target type. – Protasis

Answer 3

I think you're on the right track pursuing a [Flags] enum. You may have done this, but just in case -- making an enum flags-worthy is more than adding the attribute. You also have to specify the value for the items in a binary-friendly manner. I've found the easiest way to do this is as follows:

[Flags]
public enum IncomeType : long // you'll need the room with several options
{
    FullTime = 1,
    PartTime = 1 << 1,
    SelfEmployed = 1 << 2
    // And so on
}

If you don't do this, then you'll get sequential integer values, which breaks the bitwise comparison that allows you to do multiple values in a single integer.

Your code to create the SelectList looks fine. Your options should construct form values that get posted back with the same name. If you want to use the default modelbinder, that means the associated property on your view model would need to be List<int>. If you're not using a view model (you probably should) you can pull it out of the forms collection.

Once you have this set up, then translating from your view model to your NHibernate entity is simple if a little annoying. You basically have to cycle through the values in the list and |= them onto your NHibernate entity's single enum property.

So let's assume you have a view model like this:

public class MyEditViewModel
{
    public string Name { get; set; }
    public List<int> IncomeSelections { get; set; }

    // You'll probably have this to populate the initial view rendering
    public SelectList AllIncomeOptions { get; set; }
}

You'll build your view using your helpers and all that, then build the checkboxes using the SelectList but making sure the input name is IncomeSelections, then when it's posted back you will push the view model data into your NHibernate entity something like this:

var myNHEntity = new NHEntity(); 
// If you're editing an existing entity, then be sure to reset the enum
// value to 0 before going into the following foreach loop...

foreach (var incomeSelection in viewModel.IncomeSelections)
{
    myNHEntity.IncomeSelection |= incomeSelection;
}

There's probably a more clever way to do this, and you might have to cast the int to your enum type, but you'll figure that out (I'd do it for you, but it is Friday and I already have a beer open).

NHibernate should persist it without you having to do anything funky on the NH side.

In summary...

It seems like this is more a problem of how you handle the posted data than the NHibernate side. If you implement something like this, then be sure to use Fiddler or FireBug to inspect the posted values to make sure 1) they're integers and 2) the names are the same so they'll be added to the list.

Good luck!

Electrothermics

I appreciate the effort, but this solution is not working out well for me (with [Flags]). It's hard to implement and then leaves me scratching my head on how I would dig the number out. – Colubrine