at least you can end the stage

Common/Database/Equipment.cs

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+using Common.Resources.Proto;
+using Common.Utils.ExcelReader;
+using MongoDB.Bson;
+using MongoDB.Driver;
+
+namespace Common.Database
+{
+    public class Equipment
+    {
+        public static readonly IMongoCollection<EquipmentScheme> collection = Global.db.GetCollection<EquipmentScheme>("Equipments");
+
+        public static EquipmentScheme FromUid(uint uid)
+        {
+            return collection.AsQueryable().Where(collection => collection.OwnerUid == uid).FirstOrDefault() ?? Create(uid);
+        }
+
+        public static EquipmentScheme Create(uint uid)
+        {
+            EquipmentScheme? tryEquipment = collection.AsQueryable().Where(collection => collection.OwnerUid == uid).FirstOrDefault();
+            if (tryEquipment != null) { return tryEquipment; }
+
+            EquipmentScheme Equipment = new()
+            {
+                OwnerUid = uid,
+                MaterialList = Array.Empty<Resources.Proto.Material>(),
+                WeaponList = Array.Empty<Weapon>(),
+                StigmataList = Array.Empty<Stigmata>(),
+                MechaList = Array.Empty<Mecha>(),
+            };
+
+            collection.InsertOne(Equipment);
+
+            return Equipment;
+        }
+    }
+
+#pragma warning disable CS8618 // Non-nullable field must contain a non-null value when exiting constructor. Consider declaring as nullable.
+    public class EquipmentScheme
+    {
+        public ObjectId Id { get; set; }
+        public uint OwnerUid { get; set; }
+        public Resources.Proto.Material[] MaterialList { get; set; }
+        public Mecha[] MechaList { get; set; }
+        public Stigmata[] StigmataList { get; set; }
+        public Weapon[] WeaponList { get; set; }
+
+        public Weapon AddWeapon(int weaponId)
+        {
+            WeaponDataExcel? weaponData = WeaponData.GetInstance().FromId(weaponId);
+            if (weaponData == null) { throw new ArgumentException("Invalid weaponId"); }
+
+            Weapon weapon = new()
+            {
+                UniqueId = (uint)AutoIncrement.GetNextNumber("Weapon", 100),
+                Id = (uint)weaponData.Id,
+                Level = 1,
+                Exp = 0,
+                IsExtracted = false,
+                IsProtected = false
+            };
+
+            WeaponList = WeaponList.Append(weapon).ToArray();
+            return weapon;
+        }
+
+        public Stigmata AddStigmata(int stigmataId)
+        {
+            StigmataDataExcel? stigmataData = StigmataData.GetInstance().FromId(stigmataId);
+            if (stigmataData == null) { throw new ArgumentException("Invalid stigmataId"); }
+
+            Stigmata stigmata = new()
+            {
+                UniqueId = (uint)AutoIncrement.GetNextNumber("Stigmata", 100),
+                Id = (uint)stigmataData.Id,
+                Level = 1,
+                Exp = 0,
+                IsProtected = false,
+                SlotNum = 0,
+                RefineValue = 0,
+                PromoteTimes = 0
+            };
+
+            StigmataList = StigmataList.Append(stigmata).ToArray();
+            return stigmata;
+        }
+
+        public Resources.Proto.Material AddMaterial(int materialId, int num = 1)
+        {
+            int MaterialIndex = Array.FindIndex(MaterialList, material => material.Id == materialId);
+
+            if(MaterialIndex == -1)
+            {
+                MaterialList = MaterialList.Append(new() { Id = (uint)materialId, Num = num < 0 ? 0 : (uint)num }).ToArray();
+            }
+            else
+            {
+                if (num < 0)
+                {
+                    MaterialList[MaterialIndex].Num -= (uint)Math.Abs(num);
+                }
+                else
+                {
+                    MaterialList[MaterialIndex].Num += (uint)num;
+                }
+            }
+
+            return MaterialList.Where(material => material.Id == materialId).First();
+        }
+
+        public void Save()
+        {
+            Equipment.collection.ReplaceOne(Builders<EquipmentScheme>.Filter.Eq(equipment => equipment.Id, Id), this);
+        }
+    }
+#pragma warning restore CS8618 // Non-nullable field must contain a non-null value when exiting constructor. Consider declaring as nullable.
+}