Add MySQL-backed HRMS repositories and DB integration configuration.

1) Introduces DB connectivity, repository abstractions, and new config flags/env overrides.

2) Keeps architecture clean and isolated.

Data/DbModels.cs

@@ -0,0 +1,34 @@
+using System;
+
+namespace HikvisionAttendanceService.Data;
+
+internal sealed class AttendanceMachineRow
+{
+    public string MachineId { get; set; } = "";
+    public string MachineIp { get; set; } = "";
+    public int PortNumber { get; set; } = 8000;
+    public string MachineName { get; set; } = "";
+    public int? SiteId { get; set; }
+    public string MachineStatus { get; set; } = "";
+    public string MachineType { get; set; } = "";
+    public string Status { get; set; } = "";
+    public DateTime? LastSyncDate { get; set; }
+    public int TotalUsers { get; set; }
+}
+
+internal sealed class AttendanceMachineUserRow
+{
+    public string MachineId { get; set; } = "";
+    public string SerialNumber { get; set; } = "";
+    public string EmployeeName { get; set; } = "";
+    public bool IsDeleted { get; set; }
+    public bool IsDeletionRequested { get; set; }
+}
+
+internal sealed class AttendanceMachineFaceTemplateRow
+{
+    public string SerialNo { get; set; } = "";
+    public byte[] Template { get; set; } = Array.Empty<byte>();
+    public DateTime CreatedDate { get; set; }
+    public bool IsActive { get; set; } = true;
+}

Data/Interfaces.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Collections.Generic;
+
+namespace HikvisionAttendanceService.Data;
+
+internal interface IHrmsDbConnectionFactory
+{
+    string BuildConnectionStringMasked();
+    bool TryBuildConnectionString(out string connectionString, out string error);
+}
+
+internal interface IAttendanceMachineRepository
+{
+    List<AttendanceMachineRow> GetActiveMachines(string? machineTypeFilter, out string error);
+    void UpdateMachineSyncState(string machineIp, string status, DateTime? lastSyncDate, int? totalUsers, out string error);
+    bool TryGetMachineLastSyncDate(string machineIp, out DateTime? lastSyncDate, out string error);
+    bool UpdateMachineLastSyncDate(string machineIp, DateTime lastSyncDate, out string error);
+}
+
+internal interface IAttendanceLogRepository
+{
+    bool UpsertAttendance(
+        string acNo,
+        DateTime checkTime,
+        int processed,
+        string machineId,
+        int inOutTypeId,
+        string machineIp,
+        DateTime dateOnly,
+        out string error);
+}
+
+internal interface IAttendanceMachineUserRepository
+{
+    List<AttendanceMachineUserRow> GetActiveUsersByMachine(string machineId, out string error);
+    List<AttendanceMachineUserRow> GetPendingDeletionUsersByMachine(string machineId, out string error);
+    bool UpsertMachineUser(string machineId, string serialNumber, string employeeName, out string error);
+    bool MarkDeleted(string machineId, string serialNumber, string updatedBy, out string error);
+}
+
+internal interface IAttendanceMachineFaceTemplateRepository
+{
+    bool UpsertFaceTemplate(string serialNo, byte[] template, DateTime createdDate, bool isActive, out string error);
+    bool TryGetActiveFaceTemplateBySerial(string serialNo, out AttendanceMachineFaceTemplateRow? row, out string error);
+}

Data/MySqlHrmsDbConnectionFactory.cs

@@ -0,0 +1,55 @@
+using MySql.Data.MySqlClient;
+
+namespace HikvisionAttendanceService.Data;
+
+internal sealed class MySqlHrmsDbConnectionFactory : IHrmsDbConnectionFactory
+{
+    private readonly HikvisionAttendanceWindowsService.HikvisionServiceConfig _config;
+
+    public MySqlHrmsDbConnectionFactory(HikvisionAttendanceWindowsService.HikvisionServiceConfig config)
+    {
+        _config = config;
+    }
+
+    public string BuildConnectionStringMasked()
+    {
+        if (TryBuildConnectionString(out var cs, out _))
+        {
+            var b = new MySqlConnectionStringBuilder(cs);
+            b.Password = "***";
+            return b.ConnectionString;
+        }
+        return "(invalid)";
+    }
+
+    public bool TryBuildConnectionString(out string connectionString, out string error)
+    {
+        connectionString = "";
+        error = "";
+        if (!string.IsNullOrWhiteSpace(_config.DbConnectionString))
+        {
+            connectionString = _config.DbConnectionString.Trim();
+            return true;
+        }
+
+        if (string.IsNullOrWhiteSpace(_config.DbHost) ||
+            string.IsNullOrWhiteSpace(_config.DbUsername) ||
+            string.IsNullOrWhiteSpace(_config.DbName))
+        {
+            error = "DbHost/DbUsername/DbName are required when DbConnectionString is empty.";
+            return false;
+        }
+
+        var b = new MySqlConnectionStringBuilder
+        {
+            Server = _config.DbHost.Trim(),
+            Port = (uint)(_config.DbPort > 0 ? _config.DbPort : 3306),
+            Database = _config.DbName.Trim(),
+            UserID = _config.DbUsername.Trim(),
+            Password = _config.DbPassword ?? "",
+            DefaultCommandTimeout = 30
+        };
+        connectionString = b.ConnectionString;
+        return true;
+    }
+}

Data/MySqlRepositories.cs

@@ -0,0 +1,298 @@
+using System;
+using System.Collections.Generic;
+using MySql.Data.MySqlClient;
+
+namespace HikvisionAttendanceService.Data;
+
+internal sealed class MySqlAttendanceMachineRepository : IAttendanceMachineRepository
+{
+    private readonly IHrmsDbConnectionFactory _factory;
+    public MySqlAttendanceMachineRepository(IHrmsDbConnectionFactory factory) { _factory = factory; }
+
+    public List<AttendanceMachineRow> GetActiveMachines(string? machineTypeFilter, out string error)
+    {
+        error = "";
+        var rows = new List<AttendanceMachineRow>();
+        if (!_factory.TryBuildConnectionString(out var cs, out error))
+            return rows;
+        try
+        {
+            using var conn = new MySqlConnection(cs);
+            conn.Open();
+            string sql = "SELECT machine_id,machine_ip,port_number,machine_name,site_id,machine_status,machine_type,status,last_sync_date,total_users " +
+                         "FROM attendance_machine WHERE (machine_status='active' OR machine_status='1' OR machine_status=1)";
+            if (!string.IsNullOrWhiteSpace(machineTypeFilter))
+                sql += " AND machine_type=@machineType";
+            using var cmd = new MySqlCommand(sql, conn);
+            if (!string.IsNullOrWhiteSpace(machineTypeFilter))
+                cmd.Parameters.AddWithValue("@machineType", machineTypeFilter);
+            using var rd = cmd.ExecuteReader();
+            while (rd.Read())
+            {
+                rows.Add(new AttendanceMachineRow
+                {
+                    MachineId = rd["machine_id"]?.ToString() ?? "",
+                    MachineIp = rd["machine_ip"]?.ToString() ?? "",
+                    PortNumber = rd["port_number"] == DBNull.Value ? 8000 : Convert.ToInt32(rd["port_number"]),
+                    MachineName = rd["machine_name"]?.ToString() ?? "",
+                    SiteId = rd["site_id"] == DBNull.Value ? (int?)null : Convert.ToInt32(rd["site_id"]),
+                    MachineStatus = rd["machine_status"]?.ToString() ?? "",
+                    MachineType = rd["machine_type"]?.ToString() ?? "",
+                    Status = rd["status"]?.ToString() ?? "",
+                    LastSyncDate = rd["last_sync_date"] == DBNull.Value ? (DateTime?)null : Convert.ToDateTime(rd["last_sync_date"]),
+                    TotalUsers = rd["total_users"] == DBNull.Value ? 0 : Convert.ToInt32(rd["total_users"])
+                });
+            }
+        }
+        catch (Exception ex) { error = ex.Message; }
+        return rows;
+    }
+
+    public void UpdateMachineSyncState(string machineIp, string status, DateTime? lastSyncDate, int? totalUsers, out string error)
+    {
+        error = "";
+        if (!_factory.TryBuildConnectionString(out var cs, out error))
+            return;
+        try
+        {
+            using var conn = new MySqlConnection(cs);
+            conn.Open();
+            using var cmd = new MySqlCommand(
+                "UPDATE attendance_machine SET status=@status,last_sync_date=COALESCE(@last_sync_date,last_sync_date),total_users=COALESCE(@total_users,total_users) WHERE machine_ip=@machine_ip",
+                conn);
+            cmd.Parameters.AddWithValue("@status", status ?? "");
+            cmd.Parameters.AddWithValue("@last_sync_date", (object?)lastSyncDate ?? DBNull.Value);
+            cmd.Parameters.AddWithValue("@total_users", (object?)totalUsers ?? DBNull.Value);
+            cmd.Parameters.AddWithValue("@machine_ip", machineIp ?? "");
+            cmd.ExecuteNonQuery();
+        }
+        catch (Exception ex) { error = ex.Message; }
+    }
+
+    public bool TryGetMachineLastSyncDate(string machineIp, out DateTime? lastSyncDate, out string error)
+    {
+        lastSyncDate = null;
+        error = "";
+        if (!_factory.TryBuildConnectionString(out var cs, out error))
+            return false;
+        try
+        {
+            using var conn = new MySqlConnection(cs);
+            conn.Open();
+            using var cmd = new MySqlCommand(
+                "SELECT last_sync_date FROM attendance_machine WHERE machine_ip=@machine_ip LIMIT 1",
+                conn);
+            cmd.Parameters.AddWithValue("@machine_ip", machineIp ?? "");
+            var obj = cmd.ExecuteScalar();
+            if (obj == null || obj == DBNull.Value)
+                return true;
+            lastSyncDate = Convert.ToDateTime(obj);
+            return true;
+        }
+        catch (Exception ex)
+        {
+            error = ex.Message;
+            return false;
+        }
+    }
+
+    public bool UpdateMachineLastSyncDate(string machineIp, DateTime lastSyncDate, out string error)
+    {
+        error = "";
+        if (!_factory.TryBuildConnectionString(out var cs, out error))
+            return false;
+        try
+        {
+            using var conn = new MySqlConnection(cs);
+            conn.Open();
+            using var cmd = new MySqlCommand(
+                "UPDATE attendance_machine SET last_sync_date=@last_sync_date WHERE machine_ip=@machine_ip",
+                conn);
+            cmd.Parameters.AddWithValue("@last_sync_date", lastSyncDate);
+            cmd.Parameters.AddWithValue("@machine_ip", machineIp ?? "");
+            cmd.ExecuteNonQuery();
+            return true;
+        }
+        catch (Exception ex)
+        {
+            error = ex.Message;
+            return false;
+        }
+    }
+}
+
+internal sealed class MySqlAttendanceLogRepository : IAttendanceLogRepository
+{
+    private readonly IHrmsDbConnectionFactory _factory;
+    public MySqlAttendanceLogRepository(IHrmsDbConnectionFactory factory) { _factory = factory; }
+
+    public bool UpsertAttendance(string acNo, DateTime checkTime, int processed, string machineId, int inOutTypeId, string machineIp, DateTime dateOnly, out string error)
+    {
+        error = "";
+        if (!_factory.TryBuildConnectionString(out var cs, out error))
+            return false;
+        try
+        {
+            using var conn = new MySqlConnection(cs);
+            conn.Open();
+            using var cmd = new MySqlCommand(
+                "REPLACE INTO attendance_log (ac_no,checktime,processed,machine_id,in_out_type_id,machine_ip,date) " +
+                "VALUES (@ac_no,@checktime,@processed,@machine_id,@in_out_type_id,@machine_ip,@date)",
+                conn);
+            cmd.Parameters.AddWithValue("@ac_no", acNo ?? "");
+            cmd.Parameters.AddWithValue("@checktime", checkTime);
+            cmd.Parameters.AddWithValue("@processed", processed);
+            cmd.Parameters.AddWithValue("@machine_id", machineId ?? "");
+            cmd.Parameters.AddWithValue("@in_out_type_id", inOutTypeId);
+            cmd.Parameters.AddWithValue("@machine_ip", machineIp ?? "");
+            cmd.Parameters.AddWithValue("@date", dateOnly.Date);
+            cmd.ExecuteNonQuery();
+            return true;
+        }
+        catch (Exception ex) { error = ex.Message; return false; }
+    }
+}
+
+internal sealed class MySqlAttendanceMachineUserRepository : IAttendanceMachineUserRepository
+{
+    private readonly IHrmsDbConnectionFactory _factory;
+    public MySqlAttendanceMachineUserRepository(IHrmsDbConnectionFactory factory) { _factory = factory; }
+
+    public List<AttendanceMachineUserRow> GetActiveUsersByMachine(string machineId, out string error) =>
+        QueryUsers(machineId, false, out error);
+
+    public List<AttendanceMachineUserRow> GetPendingDeletionUsersByMachine(string machineId, out string error) =>
+        QueryUsers(machineId, true, out error);
+
+    private List<AttendanceMachineUserRow> QueryUsers(string machineId, bool deletionRequested, out string error)
+    {
+        error = "";
+        var rows = new List<AttendanceMachineUserRow>();
+        if (!_factory.TryBuildConnectionString(out var cs, out error))
+            return rows;
+        try
+        {
+            using var conn = new MySqlConnection(cs);
+            conn.Open();
+            using var cmd = new MySqlCommand(
+                "SELECT machine_id,serial_number,employee_name,is_deleted,is_deletion_requested FROM attendance_machine_user " +
+                "WHERE machine_id=@machine_id AND is_deleted=0 AND is_deletion_requested=@is_deletion_requested",
+                conn);
+            cmd.Parameters.AddWithValue("@machine_id", machineId ?? "");
+            cmd.Parameters.AddWithValue("@is_deletion_requested", deletionRequested ? 1 : 0);
+            using var rd = cmd.ExecuteReader();
+            while (rd.Read())
+            {
+                rows.Add(new AttendanceMachineUserRow
+                {
+                    MachineId = rd["machine_id"]?.ToString() ?? "",
+                    SerialNumber = rd["serial_number"]?.ToString() ?? "",
+                    EmployeeName = rd["employee_name"]?.ToString() ?? "",
+                    IsDeleted = Convert.ToInt32(rd["is_deleted"]) != 0,
+                    IsDeletionRequested = Convert.ToInt32(rd["is_deletion_requested"]) != 0
+                });
+            }
+        }
+        catch (Exception ex) { error = ex.Message; }
+        return rows;
+    }
+
+    public bool UpsertMachineUser(string machineId, string serialNumber, string employeeName, out string error)
+    {
+        error = "";
+        if (!_factory.TryBuildConnectionString(out var cs, out error))
+            return false;
+        try
+        {
+            using var conn = new MySqlConnection(cs);
+            conn.Open();
+            using var cmd = new MySqlCommand(
+                "REPLACE INTO attendance_machine_user (machine_id,serial_number,employee_name,is_deleted,is_deletion_requested,updated_at) " +
+                "VALUES (@machine_id,@serial_number,@employee_name,0,0,NOW())", conn);
+            cmd.Parameters.AddWithValue("@machine_id", machineId ?? "");
+            cmd.Parameters.AddWithValue("@serial_number", serialNumber ?? "");
+            cmd.Parameters.AddWithValue("@employee_name", employeeName ?? "");
+            cmd.ExecuteNonQuery();
+            return true;
+        }
+        catch (Exception ex) { error = ex.Message; return false; }
+    }
+
+    public bool MarkDeleted(string machineId, string serialNumber, string updatedBy, out string error)
+    {
+        error = "";
+        if (!_factory.TryBuildConnectionString(out var cs, out error))
+            return false;
+        try
+        {
+            using var conn = new MySqlConnection(cs);
+            conn.Open();
+            using var cmd = new MySqlCommand(
+                "UPDATE attendance_machine_user SET is_deleted=1,is_deletion_requested=0,updated_by=@updated_by,updated_at=NOW() " +
+                "WHERE machine_id=@machine_id AND serial_number=@serial_number", conn);
+            cmd.Parameters.AddWithValue("@updated_by", updatedBy ?? "hikvision-service");
+            cmd.Parameters.AddWithValue("@machine_id", machineId ?? "");
+            cmd.Parameters.AddWithValue("@serial_number", serialNumber ?? "");
+            cmd.ExecuteNonQuery();
+            return true;
+        }
+        catch (Exception ex) { error = ex.Message; return false; }
+    }
+}
+
+internal sealed class MySqlAttendanceMachineFaceTemplateRepository : IAttendanceMachineFaceTemplateRepository
+{
+    private readonly IHrmsDbConnectionFactory _factory;
+    public MySqlAttendanceMachineFaceTemplateRepository(IHrmsDbConnectionFactory factory) { _factory = factory; }
+
+    public bool UpsertFaceTemplate(string serialNo, byte[] template, DateTime createdDate, bool isActive, out string error)
+    {
+        error = "";
+        if (!_factory.TryBuildConnectionString(out var cs, out error))
+            return false;
+        try
+        {
+            using var conn = new MySqlConnection(cs);
+            conn.Open();
+            using var cmd = new MySqlCommand(
+                "REPLACE INTO attendance_machine_face_templates (serial_no,template,created_date,is_active) " +
+                "VALUES (@serial_no,@template,@created_date,@is_active)", conn);
+            cmd.Parameters.AddWithValue("@serial_no", serialNo ?? "");
+            cmd.Parameters.Add("@template", MySqlDbType.Blob).Value = (object?)template ?? Array.Empty<byte>();
+            cmd.Parameters.AddWithValue("@created_date", createdDate);
+            cmd.Parameters.AddWithValue("@is_active", isActive ? 1 : 0);
+            cmd.ExecuteNonQuery();
+            return true;
+        }
+        catch (Exception ex) { error = ex.Message; return false; }
+    }
+
+    public bool TryGetActiveFaceTemplateBySerial(string serialNo, out AttendanceMachineFaceTemplateRow? row, out string error)
+    {
+        row = null;
+        error = "";
+        if (!_factory.TryBuildConnectionString(out var cs, out error))
+            return false;
+        try
+        {
+            using var conn = new MySqlConnection(cs);
+            conn.Open();
+            using var cmd = new MySqlCommand(
+                "SELECT serial_no,template,created_date,is_active FROM attendance_machine_face_templates " +
+                "WHERE serial_no=@serial_no AND is_active=1 ORDER BY created_date DESC LIMIT 1", conn);
+            cmd.Parameters.AddWithValue("@serial_no", serialNo ?? "");
+            using var rd = cmd.ExecuteReader();
+            if (!rd.Read())
+                return false;
+            row = new AttendanceMachineFaceTemplateRow
+            {
+                SerialNo = rd["serial_no"]?.ToString() ?? "",
+                Template = rd["template"] == DBNull.Value ? Array.Empty<byte>() : (byte[])rd["template"],
+                CreatedDate = rd["created_date"] == DBNull.Value ? DateTime.MinValue : Convert.ToDateTime(rd["created_date"]),
+                IsActive = rd["is_active"] != DBNull.Value && Convert.ToInt32(rd["is_active"]) != 0
+            };
+            return true;
+        }
+        catch (Exception ex) { error = ex.Message; return false; }
+    }
+}

HikvisionAttendanceService.csproj

@@ -22,13 +22,10 @@
 
   <ItemGroup>
     <!-- Hikvision interop (imported directly from the SDK demo source files) -->
-    <Compile Include="D:\EN-HCNetSDKV6.1.9.48_build20230410_win32\EN-HCNetSDKV6.1.9.48_build20230410_win32\C# demo\8-ACS_Optimization_ALL\EventByDeploy\EventByDeploy\HCNetSDK.cs"
+    <Compile Include="D:\EN-HCNetSDKV6.1.9.48_build20230410_win32\EN-HCNetSDKV6.1.9.48_build20230410_win32\C# demo\8-ACS_Optimization_ALL\EventByDeploy\EventByDeploy\HCNetSDK.cs" Link="Interop\EventByDeploy\HCNetSDK.cs" />
-             Link="Interop\EventByDeploy\HCNetSDK.cs" />
+    <Compile Include="D:\EN-HCNetSDKV6.1.9.48_build20230410_win32\EN-HCNetSDKV6.1.9.48_build20230410_win32\C# demo\8-ACS_Optimization_ALL\EventByDeploy\EventByDeploy\TypeMap.cs" Link="Interop\EventByDeploy\TypeMap.cs" />
-    <Compile Include="D:\EN-HCNetSDKV6.1.9.48_build20230410_win32\EN-HCNetSDKV6.1.9.48_build20230410_win32\C# demo\8-ACS_Optimization_ALL\EventByDeploy\EventByDeploy\TypeMap.cs"
-             Link="Interop\EventByDeploy\TypeMap.cs" />
     <!-- Login_V30 + core callback helpers -->
-    <Compile Include="D:\EN-HCNetSDKV6.1.9.48_build20230410_win32\EN-HCNetSDKV6.1.9.48_build20230410_win32\C# demo\9-AppsDemo_build20201230191326\CommonBase\Head\HCNetSDK.cs"
+    <Compile Include="D:\EN-HCNetSDKV6.1.9.48_build20230410_win32\EN-HCNetSDKV6.1.9.48_build20230410_win32\C# demo\9-AppsDemo_build20201230191326\CommonBase\Head\HCNetSDK.cs" Link="Interop\AppsDemo\CommonBase\HCNetSDK_LoginV30.cs" />
-             Link="Interop\AppsDemo\CommonBase\HCNetSDK_LoginV30.cs" />
   </ItemGroup>
 
   <ItemGroup>
@@ -51,4 +48,10 @@
     <Reference Include="System.Net.Http" />
   </ItemGroup>
 
+  <ItemGroup>
+    <PackageReference Include="MySql.Data">
+      <Version>9.6.0</Version>
+    </PackageReference>
+  </ItemGroup>
+
 </Project>

HikvisionAttendanceWindowsService.cs

@@ -78,6 +78,48 @@ public sealed class HikvisionAttendanceWindowsService : ServiceBase
         [DataMember]
         public string SqlConnectionString { get; set; } = "";
 
+        [DataMember]
+        public bool EnableDbIntegration { get; set; }
+
+        [DataMember]
+        public bool EnableDbMachineLoading { get; set; }
+
+        [DataMember]
+        public bool PreferDbMachinesOverConfig { get; set; }
+
+        [DataMember]
+        public bool EnableAttendanceDbPersistence { get; set; }
+
+        [DataMember]
+        public bool EnableTemplateDbPersistence { get; set; }
+
+        [DataMember]
+        public bool EnableTemplateDbToDeviceSync { get; set; }
+
+        [DataMember]
+        public bool KeepAttendanceFileExport { get; set; } = true;
+
+        [DataMember]
+        public bool KeepTemplateFiles { get; set; } = true;
+
+        [DataMember]
+        public string DbHost { get; set; } = "";
+
+        [DataMember]
+        public int DbPort { get; set; } = 3306;
+
+        [DataMember]
+        public string DbName { get; set; } = "hrms";
+
+        [DataMember]
+        public string DbUsername { get; set; } = "";
+
+        [DataMember]
+        public string DbPassword { get; set; } = "";
+
+        [DataMember]
+        public string DbConnectionString { get; set; } = "";
+
         /// <summary>When true and SqlConnectionString is set, attendance rows are INSERTed. Default false until schema is finalized.</summary>
         [DataMember]
         public bool EnableDatabasePersistence { get; set; }
@@ -177,6 +219,20 @@ public sealed class HikvisionAttendanceWindowsService : ServiceBase
                     {
                         LogDirectory = @"C:\Users\Public\HikvisionAttendanceService",
                         SqlConnectionString = "",
+                        EnableDbIntegration = false,
+                        EnableDbMachineLoading = false,
+                        PreferDbMachinesOverConfig = false,
+                        EnableAttendanceDbPersistence = false,
+                        EnableTemplateDbPersistence = false,
+                        EnableTemplateDbToDeviceSync = false,
+                        KeepAttendanceFileExport = true,
+                        KeepTemplateFiles = true,
+                        DbHost = "",
+                        DbPort = 3306,
+                        DbName = "hrms",
+                        DbUsername = "",
+                        DbPassword = "",
+                        DbConnectionString = "",
                         EnableDatabasePersistence = false,
                         AttendanceTextFilePath = "",
                         AttendanceTableName = "dbo.HikvisionAttendanceEvents",
@@ -211,6 +267,7 @@ public sealed class HikvisionAttendanceWindowsService : ServiceBase
                     using (var ms = new MemoryStream(Encoding.UTF8.GetBytes(raw)))
                     {
                         var cfg = (HikvisionServiceConfig)serializer.ReadObject(ms);
+                        ApplyEnvironmentOverrides(cfg);
                         NormalizeLoadedDeviceConfig(cfg);
                         return cfg;
                     }
@@ -222,6 +279,7 @@ public sealed class HikvisionAttendanceWindowsService : ServiceBase
                     using (var ms = new MemoryStream(Encoding.UTF8.GetBytes(sanitized)))
                     {
                         var cfg = (HikvisionServiceConfig)serializer.ReadObject(ms);
+                        ApplyEnvironmentOverrides(cfg);
                         NormalizeLoadedDeviceConfig(cfg);
                         return cfg;
                     }
@@ -233,6 +291,20 @@ public sealed class HikvisionAttendanceWindowsService : ServiceBase
                 {
                     LogDirectory = @"C:\Users\Public\HikvisionAttendanceService",
                     SqlConnectionString = "",
+                    EnableDbIntegration = false,
+                    EnableDbMachineLoading = false,
+                    PreferDbMachinesOverConfig = false,
+                    EnableAttendanceDbPersistence = false,
+                    EnableTemplateDbPersistence = false,
+                    EnableTemplateDbToDeviceSync = false,
+                    KeepAttendanceFileExport = true,
+                    KeepTemplateFiles = true,
+                    DbHost = "",
+                    DbPort = 3306,
+                    DbName = "hrms",
+                    DbUsername = "",
+                    DbPassword = "",
+                    DbConnectionString = "",
                     EnableDatabasePersistence = false,
                     AttendanceTextFilePath = "",
                     AttendanceTableName = "dbo.HikvisionAttendanceEvents",
@@ -347,6 +419,34 @@ public sealed class HikvisionAttendanceWindowsService : ServiceBase
             return sb.ToString();
         }
 
+        private static void ApplyEnvironmentOverrides(HikvisionServiceConfig cfg)
+        {
+            if (cfg == null)
+                return;
+
+            string ReadEnv(string key) => Environment.GetEnvironmentVariable(key) ?? "";
+
+            var cs = ReadEnv("HIKVISION_DB_CONNECTION_STRING");
+            var host = ReadEnv("HIKVISION_DB_HOST");
+            var user = ReadEnv("HIKVISION_DB_USERNAME");
+            var pass = ReadEnv("HIKVISION_DB_PASSWORD");
+            var dbName = ReadEnv("HIKVISION_DB_NAME");
+            var dbPort = ReadEnv("HIKVISION_DB_PORT");
+
+            if (!string.IsNullOrWhiteSpace(cs))
+                cfg.DbConnectionString = cs.Trim();
+            if (!string.IsNullOrWhiteSpace(host))
+                cfg.DbHost = host.Trim();
+            if (!string.IsNullOrWhiteSpace(user))
+                cfg.DbUsername = user.Trim();
+            if (!string.IsNullOrWhiteSpace(pass))
+                cfg.DbPassword = pass;
+            if (!string.IsNullOrWhiteSpace(dbName))
+                cfg.DbName = dbName.Trim();
+            if (int.TryParse(dbPort, out var parsedPort) && parsedPort > 0)
+                cfg.DbPort = parsedPort;
+        }
+
         private static void NormalizeLoadedDeviceConfig(HikvisionServiceConfig? cfg)
         {
             if (cfg == null)