Trying to save comma-separated list - asp.net-mvc-3

Question

Trying to save selections from a CheckBoxList as a comma-separated list (string) in DB (one or more choices selected). I am using a proxy in order to save as a string because otherwise I'd have to create separate tables in the DB for a relation - the work is not worth it for this simple scenario and I was hoping that I could just convert it to a string and avoid that.
The CheckBoxList uses an enum for it's choices:
public enum Selection
{
Selection1,
Selection2,
Selection3
}
Not to be convoluted, but I use [Display(Name="Choice 1")] and an extension class to display something friendly on the UI. Not sure if I can save that string instead of just the enum, although I think if I save as enum it's not a big deal for me to "display" the friendly string on UI on some confirmation page.
This is the "Record" class that saves a string in the DB:
public virtual string MyCheckBox { get; set; }
This is the "Proxy", which is some sample I found but not directly dealing with enum, and which uses IEnumerable<string> (or should it be IEnumerable<Selection>?):
public IEnumerable<string> MyCheckBox
{
get
{
if (String.IsNullOrWhiteSpace(Record.MyCheckBox)) return new string[] { };
return Record
.MyCheckBox
.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries)
.Select(r => r.Trim())
.Where(r => !String.IsNullOrEmpty(r));
}
set
{
Record.MyCheckBox = value == null ? null : String.Join(",", value);
}
}
To save in the DB, I am trying to do this in a create class:
proxy.MyCheckBox = record.MyCheckBox; //getting error here
but am getting the error:
Cannot implicitly convert 'string' to System.Collections.Generic.IEnumerable'
I don't know, if it's possible or better, to use Parse or ToString from the API for enum values.
I know that doing something like this will store whatever I put in the ("") into the DB, so it's just a matter of figuring out how to overcome the error (or, if there is an alternative):
proxy.MyCheckBox = new[] {"foo", "bar"};
I am not good with this stuff and have just been digging and digging to come up with a solution. Any help is much appreciated.

Answer 1

You can accomplish this using a custom user type. The example below uses an ISet<string> on the class and stores the values as a delimited string.
[Serializable]
public class CommaDelimitedSet : IUserType
{
const string delimiter = ",";
#region IUserType Members
public new bool Equals(object x, object y)
{
if (ReferenceEquals(x, y))
{
return true;
}
var xSet = x as ISet<string>;
var ySet = y as ISet<string>;
if (xSet == null || ySet == null)
{
return false;
}
// compare set contents
return xSet.Except(ySet).Count() == 0 && ySet.Except(xSet).Count() == 0;
}
public int GetHashCode(object x)
{
return x.GetHashCode();
}
public object NullSafeGet(IDataReader rs, string[] names, object owner)
{
var outValue = NHibernateUtil.String.NullSafeGet(rs, names[0]) as string;
if (string.IsNullOrEmpty(outValue))
{
return new HashSet<string>();
}
else
{
var splitArray = outValue.Split(new[] {Delimiter}, StringSplitOptions.RemoveEmptyEntries);
return new HashSet<string>(splitArray);
}
}
public void NullSafeSet(IDbCommand cmd, object value, int index)
{
var inValue = value as ISet<string>;
object setValue = inValue == null ? null : string.Join(Delimiter, inValue);
NHibernateUtil.String.NullSafeSet(cmd, setValue, index);
}
public object DeepCopy(object value)
{
// return new ISet so that Equals can work
// see http://www.mail-archive.com/nhusers#googlegroups.com/msg11054.html
var set = value as ISet<string>;
if (set == null)
{
return null;
}
return new HashSet<string>(set);
}
public object Replace(object original, object target, object owner)
{
return original;
}
public object Assemble(object cached, object owner)
{
return DeepCopy(cached);
}
public object Disassemble(object value)
{
return DeepCopy(value);
}
public SqlType[] SqlTypes
{
get { return new[] {new SqlType(DbType.String)}; }
}
public Type ReturnedType
{
get { return typeof(ISet<string>); }
}
public bool IsMutable
{
get { return false; }
}
#endregion
}
Usage in mapping file:
Map(x => x.CheckboxValues.CustomType<CommaDelimitedSet>();