Reputation: 72868
I've got an object that uses System.Version as a property. I want this object to be mapped into my table, storing the version as a string. what's the best way to go about doing this with NHibernate v1.2?
public class MyClass
{
public Version MyVersion {get; set;}
}
not sure what to do with the propery mapping
<property name="MyVersion" column="MyVersion" not-null="true" />
this gives me errors saying "Invalid attempt to GetBytes on column 'MyVersion0_0_'. The GetBytes function can only be used on columns of type Text, NText, or Image." If I use type="string" in the map, i get casting errors.
suggestions?
Upvotes: 3
Views: 763
Reputation: 2518
Another thumbs-up for David M's answer. However, you'll note that System.Version
has a constructor that takes a string representation, as well as a ToString()
that produces the same format, so you could map the property as a simple string in NHibernate and map it to a private string field directly, then have a facade property typed to System.Version something like this:
public System.Version Version
{
get { return new System.Version(_versionAsString); }
set { _versionAsString = value.ToString(); }
}
I don't see it as bad practice particularly, and it's easy enough to do. You might need to use an internal property rather than a field if you're going to proxy the type for lazy-loading, but otherwise it should work.
Upvotes: 2
Reputation: 72868
David M's suggestion and article link were great. Just in case anyone else has problems getting to that site, though ( i had to load it up from google cache), here is my solution:
public abstract class BaseImmutableUserType : IUserType
{
public abstract object NullSafeGet(IDataReader rs, string[] names, object owner);
public abstract void NullSafeSet(IDbCommand cmd, object value, int index);
public abstract SqlType[] SqlTypes { get; }
public new bool Equals(object x, object y)
{
if (ReferenceEquals(x, y))
{
return true;
}
if (x == null || y == null)
{
return false;
}
return x.Equals(y);
}
public int GetHashCode(object x)
{
return x.GetHashCode();
}
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 DeepCopy(cached);
}
public object Disassemble(object value)
{
return DeepCopy(value);
}
public Type ReturnedType
{
get { return typeof(T); }
}
public bool IsMutable
{
get { return false; }
}
}
public class VersionUserType: BaseImmutableUserType
{
public override SqlType[] SqlTypes
{
get
{
return new SqlType[]{new StringSqlType()};
}
}
public override object NullSafeGet(IDataReader rs, string[] names, object owner)
{
Version version = null;
var value = NHibernateUtil.String.NullSafeGet(rs, names) as string;
if (value != null)
version = new Version(value);
return version;
}
public override void NullSafeSet(IDbCommand cmd, object value, int index)
{
object valueToSet;
Version version = value as Version;
if (version != null)
{
valueToSet = version.ToString();
}
else
{
valueToSet = DBNull.Value;
}
NHibernateUtil.String.NullSafeSet(cmd, valueToSet, index);
}
}
and the mapping file now has this property:
<property name="MyVersion" column="MyVersion" not-null="true" type="My.Namespace.VersionUserType, My.Assembly" />
Upvotes: 2
Reputation: 1831
David M's answer is probably the most robust way to go about it.
As an alternative, you could convert the property to a string and just use that. I'm not sure how big a change that is in your model though.
Upvotes: 0