ModernUO/dev-docs/runuo-migration-docs/09-items-mobiles-creatures.md

Items, Mobiles & Creatures Migration

Overview

Most RunUO migration work involves converting Item, Mobile, and BaseCreature subclasses. This doc combines all prior system changes (serialization, timers, property lists, naming) into complete step-by-step conversion guides for the most common content types.

Item Migration Step-by-Step

1. Apply Foundation Changes

• File-scoped namespace
• using ModernUO.Serialization;
• Rename m_ fields to _camelCase
• [Constructable] → [Constructible]
• Replace Console.WriteLine with logging
• Replace DateTime.UtcNow with Core.Now

2. Add Serialization Attributes

[SerializationGenerator(N, false)]  // N = old version + 1; false if old Deserialize used ReadInt()
public partial class MyItem : Item  // Add partial

3. Convert Fields to [SerializableField]

// RunUO
private int m_Charges;
[CommandProperty(AccessLevel.GameMaster)]
public int Charges { get { return m_Charges; } set { m_Charges = value; InvalidateProperties(); } }

// ModernUO
[SerializableField(0)]
[InvalidateProperties]
[SerializedCommandProperty(AccessLevel.GameMaster)]
private int _charges;
// Property auto-generated with InvalidateProperties

4. Delete Boilerplate

• Delete public MyItem(Serial serial) : base(serial) { }
• Delete public override void Serialize(GenericWriter writer) { ... }
• Delete public override void Deserialize(GenericReader reader) { ... }

5. Convert Timer Fields

// RunUO
private InternalTimer m_Timer;
// + nested Timer class

// ModernUO
private TimerExecutionToken _timerToken;
// + direct Timer.StartTimer() calls
// + [AfterDeserialization] for timer restoration
// + OnAfterDelete() for timer cancellation

6. Convert GetProperties

// RunUO
public override void GetProperties(ObjectPropertyList list)
{
    base.GetProperties(list);
    list.Add(1060741, m_Charges.ToString());
}

// ModernUO
public override void GetProperties(IPropertyList list)
{
    base.GetProperties(list);
    list.Add(1060741, $"{_charges}");
}

7. Convert Context Menus (if present)

// RunUO
public override void GetContextMenuEntries(Mobile from, List<ContextMenuEntry> list)
{
    base.GetContextMenuEntries(from, list);
    list.Add(new MyEntry(this));
}

// ModernUO
public override void GetContextMenuEntries(Mobile from, ref PooledRefList<ContextMenuEntry> list)
{
    base.GetContextMenuEntries(from, ref list);
    list.Add(new MyEntry(this));
}

Complete Before/After: Item

RunUO:

using System;
using Server;
using Server.Network;

namespace Server.Items
{
    public class MagicLantern : Item
    {
        private int m_Charges;
        private Mobile m_Owner;
        private InternalTimer m_Timer;

        [CommandProperty(AccessLevel.GameMaster)]
        public int Charges
        {
            get { return m_Charges; }
            set { m_Charges = value; InvalidateProperties(); }
        }

        [CommandProperty(AccessLevel.GameMaster)]
        public Mobile Owner
        {
            get { return m_Owner; }
            set { m_Owner = value; }
        }

        [Constructable]
        public MagicLantern() : base(0xA25)
        {
            m_Charges = Utility.RandomMinMax(5, 15);
            Weight = 2.0;
            Light = LightType.Circle300;
            Name = "a magic lantern";

            m_Timer = new InternalTimer(this);
            m_Timer.Start();
        }

        public MagicLantern(Serial serial) : base(serial) { }

        public override void OnDelete()
        {
            if (m_Timer != null)
                m_Timer.Stop();

            base.OnDelete();
        }

        public override void GetProperties(ObjectPropertyList list)
        {
            base.GetProperties(list);
            list.Add(1060741, m_Charges.ToString());
        }

        public override void OnDoubleClick(Mobile from)
        {
            if (!IsChildOf(from.Backpack))
            {
                from.SendLocalizedMessage(1042001);
                return;
            }

            if (m_Charges <= 0)
            {
                from.SendMessage("The lantern is depleted.");
                return;
            }

            m_Charges--;
            InvalidateProperties();
            from.SendMessage("The lantern flares brightly!");
        }

        public override void Serialize(GenericWriter writer)
        {
            base.Serialize(writer);
            writer.Write((int)1); // version

            writer.Write(m_Owner);
            writer.Write(m_Charges);
        }

        public override void Deserialize(GenericReader reader)
        {
            base.Deserialize(reader);
            int version = reader.ReadInt();

            switch (version)
            {
                case 1:
                    m_Owner = reader.ReadMobile();
                    goto case 0;
                case 0:
                    m_Charges = reader.ReadInt();
                    break;
            }

            m_Timer = new InternalTimer(this);
            m_Timer.Start();
        }

        private void Glow()
        {
            if (m_Charges > 0)
                Effects.SendLocationParticles(this, 0x376A, 9, 10, 5042);
        }

        private class InternalTimer : Timer
        {
            private MagicLantern m_Lantern;

            public InternalTimer(MagicLantern lantern) : base(TimeSpan.FromSeconds(3), TimeSpan.FromSeconds(3))
            {
                m_Lantern = lantern;
                Priority = TimerPriority.OneSecond;
            }

            protected override void OnTick()
            {
                m_Lantern.Glow();
            }
        }
    }
}

ModernUO:

using ModernUO.Serialization;

namespace Server.Items;

[SerializationGenerator(0)]
public partial class MagicLantern : Item
{
    [SerializableField(0)]
    [InvalidateProperties]
    [SerializedCommandProperty(AccessLevel.GameMaster)]
    private int _charges;

    [SerializableField(1)]
    [SerializedCommandProperty(AccessLevel.GameMaster)]
    private Mobile _owner;

    private TimerExecutionToken _glowTimer;

    [Constructible]
    public MagicLantern() : base(0xA25)
    {
        _charges = Utility.RandomMinMax(5, 15);
        Weight = 2.0;
        Light = LightType.Circle300;
        StartGlow();
    }

    public override string DefaultName => "a magic lantern";

    private void StartGlow()
    {
        Timer.StartTimer(TimeSpan.FromSeconds(3), TimeSpan.FromSeconds(3), Glow, out _glowTimer);
    }

    [AfterDeserialization]
    private void AfterDeserialization() => StartGlow();

    public override void OnAfterDelete()
    {
        _glowTimer.Cancel();
        base.OnAfterDelete();
    }

    public override void GetProperties(IPropertyList list)
    {
        base.GetProperties(list);
        list.Add(1060741, $"{_charges}");
    }

    public override void OnDoubleClick(Mobile from)
    {
        if (!IsChildOf(from.Backpack))
        {
            from.SendLocalizedMessage(1042001);
            return;
        }

        if (_charges <= 0)
        {
            from.SendMessage("The lantern is depleted.");
            return;
        }

        Charges--;
        from.SendMessage("The lantern flares brightly!");
    }

    private void Glow()
    {
        if (_charges > 0)
            Effects.SendLocationParticles(this, 0x376A, 9, 10, 5042);
    }
}

What changed:

• File-scoped namespace
• partial class + [SerializationGenerator(0)] (omit encoded parameter)
• [Constructable] → [Constructible]
• m_Charges/m_Owner → _charges/_owner with [SerializableField]
• Manual properties → auto-generated with [SerializedCommandProperty]
• InvalidateProperties() in setter → [InvalidateProperties] attribute
• Name = "..." → DefaultName => property override
• Serial constructor deleted
• Serialize/Deserialize deleted
• Nested InternalTimer class → Timer.StartTimer() + TimerExecutionToken
• Timer in Deserialize → [AfterDeserialization]
• OnDelete() timer stop → OnAfterDelete() + _token.Cancel()
• ObjectPropertyList → IPropertyList
• GetProperties uses string interpolation with holes

BaseCreature Migration

BaseCreature subclasses follow the same pattern as items but have additional considerations.

Key Differences from Items

1. Constructor calls base(AIType, FightMode) instead of base(itemID)
2. Stats set with SetStr(), SetDex(), SetInt(), etc.
3. Damage/resistance types set explicitly
4. GenerateLoot() override for loot tables
5. Many property overrides (CorpseName, Meat, Hides, etc.)

Before/After: Simple Creature

RunUO:

namespace Server.Mobiles
{
    [CorpseName("a wolf corpse")]
    public class ForestWolf : BaseCreature
    {
        [Constructable]
        public ForestWolf() : base(AIType.AI_Melee, FightMode.Closest, 10, 1, 0.2, 0.4)
        {
            Name = "a forest wolf";
            Body = 225;
            BaseSoundID = 0xE5;

            SetStr(80, 120);
            SetDex(90, 110);
            SetInt(20, 40);

            SetHits(60, 80);

            SetDamage(8, 14);

            SetDamageType(ResistanceType.Physical, 100);

            SetResistance(ResistanceType.Physical, 25, 35);

            SetSkill(SkillName.MagicResist, 30.0, 50.0);
            SetSkill(SkillName.Tactics, 50.0, 70.0);
            SetSkill(SkillName.Wrestling, 50.0, 70.0);

            Fame = 600;
            Karma = 0;

            VirtualArmor = 28;

            Tamable = true;
            ControlSlots = 1;
            MinTameSkill = 50.1;
        }

        public ForestWolf(Serial serial) : base(serial) { }

        public override int Meat { get { return 1; } }
        public override int Hides { get { return 6; } }
        public override FoodType FavoriteFood { get { return FoodType.Meat; } }
        public override PackInstinct PackInstinct { get { return PackInstinct.Canine; } }

        public override void GenerateLoot()
        {
            AddLoot(LootPack.Meager);
        }

        public override void Serialize(GenericWriter writer)
        {
            base.Serialize(writer);
            writer.Write((int)0);
        }

        public override void Deserialize(GenericReader reader)
        {
            base.Deserialize(reader);
            int version = reader.ReadInt();
        }
    }
}

ModernUO:

using ModernUO.Serialization;

namespace Server.Mobiles;

[SerializationGenerator(0)]
public partial class ForestWolf : BaseCreature
{
    [Constructible]
    public ForestWolf() : base(AIType.AI_Melee, FightMode.Closest)
    {
        Body = 225;
        BaseSoundID = 0xE5;

        SetStr(80, 120);
        SetDex(90, 110);
        SetInt(20, 40);

        SetHits(60, 80);

        SetDamage(8, 14);

        SetDamageType(ResistanceType.Physical, 100);

        SetResistance(ResistanceType.Physical, 25, 35);

        SetSkill(SkillName.MagicResist, 30.0, 50.0);
        SetSkill(SkillName.Tactics, 50.0, 70.0);
        SetSkill(SkillName.Wrestling, 50.0, 70.0);

        Fame = 600;
        Karma = 0;

        VirtualArmor = 28;

        Tamable = true;
        ControlSlots = 1;
        MinTameSkill = 50.1;
    }

    public override string CorpseName => "a wolf corpse";
    public override string DefaultName => "a forest wolf";
    public override int Meat => 1;
    public override int Hides => 6;
    public override FoodType FavoriteFood => FoodType.Meat;
    public override PackInstinct PackInstinct => PackInstinct.Canine;

    public override void GenerateLoot()
    {
        AddLoot(LootPack.Meager);
    }
}

What changed:

• [CorpseName("...")] attribute → CorpseName property override
• Name = "..." → DefaultName property override
• BaseCreature(AI, Fight, 10, 1, 0.2, 0.4) → BaseCreature(AI, Fight) (extra params have defaults)
• Expression-bodied property overrides
• Serialization boilerplate removed
• Serial constructor removed

Key Creature Constructor Differences

// RunUO — many parameters
public ForestWolf() : base(AIType.AI_Melee, FightMode.Closest, 10, 1, 0.2, 0.4)
// 10 = RangePerception, 1 = RangeFight, 0.2 = ActiveSpeed, 0.4 = PassiveSpeed

// ModernUO — simplified (defaults built in)
public ForestWolf() : base(AIType.AI_Melee, FightMode.Closest)

The extra parameters (RangePerception, RangeFight, ActiveSpeed, PassiveSpeed) have sensible defaults. Only specify them if they differ from defaults.

Common Creature Attribute Changes

RunUO	ModernUO
[CorpseName("a corpse")] attribute	public override string CorpseName => "a corpse";
Name = "a creature" in constructor	public override string DefaultName => "a creature";
get { return value; }	=> value; expression-bodied

AI Movement: No run Argument

RunUO's movement calls took a run flag that callers set inconsistently (true in combat, false for pets, gated by dist > 5 inside MoveTo). The flag only selects the client's per-step animation time, so ModernUO derives it from the creature's step pace (BaseAI.ShouldRun) and the parameter is gone:

// RunUO
MoveTo(combatant, true, m_Mobile.RangeFight);
WalkMobileRange(m_Mobile.ControlMaster, 1, false, 0, 1);

// ModernUO
MoveTo(combatant, Mobile.RangeFight);
WalkMobileRange(Mobile.ControlMaster, 1, 0, 1);

ApproachTarget, MoveToPoint and PathFollower.Follow lose the argument the same way. To make a creature run, make it fast (SetMoveSpeed / npc-speeds.json), not flagged. An isolated step (after the creature stood for at least a walk interval) goes out as a walk regardless of pace — only a continuing cadence, or a pace faster than the run interpolation, flags run.

Retaliation: OnAggressiveAction Returns bool

RunUO's BaseAI.OnAggressiveAction was a void hook that only swapped to a closer aggressor; BaseCreature.AggressiveAction then decided the response itself and set Combatant regardless of what the AI had done. ModernUO moves the whole retaliation policy into the hook — the stand-down verdict for commanded pets, the closer-aggressor swap (PreferCloserAggressor), and the IssueOrder(Attack) vs Combatant = choice — and BaseCreature only runs its bookkeeping (StopFlee, ForceReacquire, ethics shield) when the hook returns true:

// RunUO — swap only; BaseCreature picks the combatant afterwards
public override void OnAggressiveAction(Mobile aggressor)
{
    if (m_Mobile.Combatant == null)
    {
        m_Mobile.Combatant = aggressor;
        return;
    }

    base.OnAggressiveAction(aggressor);
}

// ModernUO — the AI owns the response; false = stood down, nothing else fires
public override bool OnAggressiveAction(Mobile aggressor)
{
    if (Mobile.Combatant == null)
    {
        Mobile.Combatant = aggressor;
    }
    else
    {
        PreferCloserAggressor(aggressor);
    }

    return true;
}

An override that used to return; early to refuse a fight now returns false; calling base.OnAggressiveAction runs the full stock policy, including setting Combatant, so an AI that only wants the closer-aggressor swap calls PreferCloserAggressor instead.

Masters: One Reference, Not Two

RunUO kept ControlMaster and SummonMaster as two independent fields. ModernUO stores one Master. ControlMaster and SummonMaster are views of it gated by Controlled and Summoned, and GetMaster() is ControlMaster ?? SummonMaster (see dev-docs/content-patterns.md § Masters).

ControlMaster != null implies Controlled, so a bare ControlMaster check needs no Controlled in front of it.

Assignments compile unchanged, because both setters assign Master. Reads need a look:

RunUO	ModernUO
bc.ControlMaster ?? bc.SummonMaster	bc.GetMaster()
bc.Controlled && bc.ControlMaster == m || bc.Summoned && bc.SummonMaster == m	bc.GetMaster() == m
Controlled && ControlMaster == m (m non-null)	ControlMaster == m
SummonMaster on a creature that sets it without Summoned = true (RunUO's BaseEnraged)	Master

Gotchas:

• A summon master without Summoned reads back null. A RunUO creature that assigned SummonMaster = caster; without Summoned = true and later read SummonMaster now reads null. The write still compiles; only the read changes. Use Master for both, and override IsEnemy if the creature must never target its master (see BaseEnraged).
• One master per creature. SummonMaster = x on a tamed pet replaces its owner, and ControlMaster = null on an uncontrolled summon clears its caster. Code that tracked a different owner and summoner keeps only the last assignment.
• ControlMaster = x; is not a tame. The setter only moves follower slots. It skips everything SetControlMaster(x) does: raising Controlled, checking the follower cap, resetting the order and ControlTarget, unlinking from the spawner, clearing the waypoint, home and guild. On its own it leaves a creature that uses up x's follower slots, can't be commanded and still reads as wild. Use SetControlMaster(x).
• SetControlMaster(null) keeps an uncontrolled summon's caster. It clears the master only while the creature is Controlled.

Target Acquisition: AcquireOnApproach Is a Delay

RunUO's AcquireOnApproach bool (paragon insta-aggro on approach) is now AcquireOnApproachDelay, a TimeSpan reaction-time gradient that applies to every creature — enemy movement inside AcquireOnApproachRange schedules a scan within the delay instead of waiting out the 10 s ReacquireDelay poll:

// RunUO
public override bool AcquireOnApproach => true;

// ModernUO — Zero is the old instant behavior; larger values are dumber
public override TimeSpan AcquireOnApproachDelay => TimeSpan.Zero;

AcquireOnApproachRange stays 10 for all creatures (reactive aggro is on-screen; the periodic ReacquireDelay scan still sweeps the full RangePerception). The acquired target comes from the normal FightMode-ranked scan, not from whichever mobile happened to move. See content-patterns.md § Target Acquisition.

Damage Entries: Inline ValueLinkList, Not List<DamageEntry>

RunUO's Mobile.DamageEntries was a List<DamageEntry> allocated for every mobile. ModernUO keeps damage entries in an inline ValueLinkList<DamageEntry> struct held by the mobile itself, ordered least recent → most recent, so a mobile that never takes damage owns no list object and RegisterDamage relinks in O(1). The property is ref readonly; expired entries are pruned when it is read.

// RunUO
for (var i = m.DamageEntries.Count - 1; i >= 0; --i)
{
    var de = m.DamageEntries[i];          // indexer
    ...
}
m.DamageEntries.Clear();
var rights = BaseCreature.GetLootingRights(m.DamageEntries, m.HitsMax); // List<DamageEntry>

// ModernUO — needs `using Server.Collections;` for the enumerator extensions
foreach (var de in m.DamageEntries.ByDescending()) // most recent first
{
    ...
}
foreach (var de in m.DamageEntries)                // least recent first
{
    ...
}
m.ClearDamageEntries();
var rights = BaseCreature.GetLootingRights(m.DamageEntries, m.HitsMax); // in ValueLinkList<DamageEntry>

What no longer compiles: the indexer, .Add, .Remove, .RemoveAt, .Clear, and passing the property where a List<DamageEntry> is expected. .Count, FindDamageEntryFor, FindMostRecentDamager and the other Find* methods, and RegisterDamage are unchanged. DamageEntry now carries Next/Previous/OnLinkList link fields; never set them yourself, and never call a ValueLinkList mutator on the ref readonly property — it compiles against a copy and corrupts the node's link state. Mutate only through RegisterDamage and ClearDamageEntries.

Item Name Changes

// RunUO
Name = "a magic gem";  // Set in constructor

// ModernUO — prefer property overrides
public override string DefaultName => "a magic gem";
// OR for cliloc:
public override int LabelNumber => 1234567;

Equipment/Weapon/Armor Migration

Weapons and armor follow the same item pattern but inherit from specialized base classes:

// ModernUO weapon example
[SerializationGenerator(0)]
public partial class MySpecialSword : BaseSword
{
    [Constructible]
    public MySpecialSword() : base(0x13FF) // Katana graphic
    {
        Weight = 6.0;
        Layer = Layer.TwoHanded;
    }

    public override string DefaultName => "a special sword";
    public override int AosStrengthReq => 25;
    public override int AosMinDamage => 11;
    public override int AosMaxDamage => 13;
    public override int AosSpeed => 44;
    public override float MlSpeed => 2.50f;
}

Common Base Classes

RunUO	ModernUO	Notes
BaseWeapon	BaseWeapon	Same, add partial
BaseSword / BaseMace / etc.	Same	Same, add partial
BaseArmor	BaseArmor	Same, add partial
BaseClothing	BaseClothing	Same, add partial
BaseJewel	BaseJewel	Same, add partial
BaseContainer	BaseContainer	Same, add partial
Food	Food	Same, add partial
BasePotion	BasePotion	Same, add partial

Edge Cases & Gotchas

1. [TypeAlias] for Save Compatibility

If a class changed namespace or name, use [TypeAlias]:

[TypeAlias("Server.Items.OldName")]
[SerializationGenerator(0)]
public partial class NewName : Item { }

2. OnDoubleClick Validation

ModernUO patterns prefer:

if (!IsChildOf(from.Backpack))
{
    from.SendLocalizedMessage(1042001);
    return;
}

3. CorpseName as Property Override

RunUO uses [CorpseName] attribute. ModernUO uses a property override instead.

4. SetMana(0) for Non-Casters

Always call SetMana(0) for creatures that shouldn't have mana.

5. Decrement via Generated Property

Use the generated property name (PascalCase) when decrementing to trigger dirty tracking:

Charges--;  // Uses generated property — triggers MarkDirty + InvalidateProperties
// NOT: _charges--;  // Bypasses tracking

See Also

• dev-docs/content-patterns.md — ModernUO content creation patterns
• dev-docs/serialization.md — Serialization system
• 02-serialization.md — Serialization migration details
• 03-timers.md — Timer migration
• 06-property-lists.md — Property list migration