Pandatech.SharedKernel

Opinionated ASP.NET Core 10 infrastructure library for PandaTech projects. It consolidates logging, OpenAPI, validation, CORS, SignalR, telemetry, health checks, maintenance mode, and resilience into a single package so every service starts from the same baseline.

The package is publicly available but is designed for internal use. If you want to adopt it, fork the repository and customize it to your own conventions.

Requires .NET 10.0. Uses C# 14 extension members throughout and cannot be downgraded to earlier TFMs.

---

Table of Contents

1. Installation
2. Quick Start
3. Assembly Registry
4. OpenAPI
5. Logging
6. MediatR and FluentValidation
7. CORS
8. Resilience Pipelines
9. Controllers
10. SignalR
11. OpenTelemetry
12. Health Checks
13. Maintenance Mode
14. Utilities

---

Installation

dotnet add package Pandatech.SharedKernel

---

Quick Start

A complete Program.cs using every major feature:

var builder = WebApplication.CreateBuilder(args);

builder.LogStartAttempt();
AssemblyRegistry.Add(typeof(Program).Assembly);

builder
   .ConfigureWithPandaVault()
   .AddSerilog(LogBackend.ElasticSearch)
   .AddResponseCrafter(NamingConvention.ToSnakeCase)
   .AddOpenApi()
   .AddMaintenanceMode()
   .AddOpenTelemetry()
   .AddMinimalApis(AssemblyRegistry.ToArray())
   .AddControllers(AssemblyRegistry.ToArray())
   .AddMediatrWithBehaviors(AssemblyRegistry.ToArray())
   .AddResilienceDefaultPipeline()
   .AddDistributedSignalR("localhost:6379", "app_name")
   .AddCors()
   .AddOutboundLoggingHandler()
   .AddHealthChecks();

var app = builder.Build();

app
   .UseRequestLogging()
   .UseMaintenanceMode()
   .UseResponseCrafter()
   .UseCors()
   .MapMinimalApis()
   .EnsureHealthy()
   .MapHealthCheckEndpoints()
   .MapPrometheusExporterEndpoints()
   .ClearAssemblyRegistry()
   .UseOpenApi()
   .MapControllers();

app.LogStartSuccess();
app.Run();

---

Assembly Registry

AssemblyRegistry is a thread-safe static list used to pass your project's assemblies from the builder phase to the app phase without repeating typeof(Program).Assembly everywhere.

// Add once at startup
AssemblyRegistry.Add(typeof(Program).Assembly);

// Pass to any method that needs to scan for handlers, validators, or endpoints
builder.AddMediatrWithBehaviors(AssemblyRegistry.ToArray());

// Clear after app is built to free memory — the scanning is complete
app.ClearAssemblyRegistry();

---

OpenAPI

Wraps Microsoft.AspNetCore.OpenApi with SwaggerUI and Scalar, supporting multiple API documents, custom security schemes, and enum string descriptions.

Registration

builder.AddOpenApi();
var app = builder.Build();
app.UseOpenApi();

Custom schema transformers can be added via the options callback:

builder.AddOpenApi(options =>
{
    options.AddSchemaTransformer<MyCustomTransformer>();
});

Configuration

{
    "OpenApi": {
        "DisabledEnvironments": [
            "Production"
        ],
        "SecuritySchemes": [
            {
                "HeaderName": "Authorization",
                "Description": "Bearer access token."
            },
            {
                "HeaderName": "Client-Type",
                "Description": "Identifies the client type, e.g. '2'."
            }
        ],
        "Documents": [
            {
                "Title": "Admin Panel",
                "Description": "Internal administrative endpoints.",
                "GroupName": "admin-v1",
                "Version": "v1",
                "ForExternalUse": false
            },
            {
                "Title": "Integration",
                "Description": "Public integration endpoints.",
                "GroupName": "integration-v1",
                "Version": "v1",
                "ForExternalUse": true
            }
        ],
        "Contact": {
            "Name": "Pandatech",
            "Url": "https://pandatech.it",
            "Email": "info@pandatech.it"
        }
    }
}

UI URLs

UI	URL	Notes
Swagger	/swagger	All documents
Swagger	/swagger/integration-v1	External documents only (ForExternalUse)
Scalar	/scalar/admin-v1	One URL per document
Scalar	/scalar/integration-v1	One URL per document

ForExternalUse: true creates a dedicated Swagger URL you can share with external partners while keeping internal documents private. All documents still appear on the main /swagger page.

---

Logging

Wraps Serilog with structured output, request/response logging middleware, outbound HTTP logging, and automatic log cleanup.

Registration

// Synchronous sinks — safe for up to ~1000 req/s per pod
builder.AddSerilog(LogBackend.Loki);

// Asynchronous sinks — better throughput, small risk of losing logs on hard crash
builder.AddSerilog(
    logBackend: LogBackend.ElasticSearch,
    logAdditionalProperties: new Dictionary<string, string>
    {
        ["ServiceName"] = "my-service"
    },
    daysToRetain: 14,
    asyncSinks: true
);

Log Backends

Value	Output format
None	Console only, no file output
ElasticSearch	ECS JSON to file (forward with Filebeat/Logstash)
Loki	Loki JSON to file (forward with Promtail)
CompactJson	Compact JSON to file

Environment behavior

Environment	Console	File
Local	Yes	No
Development / QA	Yes	Yes
Production	No	Yes

Configuration

{
    "Serilog": {
        "MinimumLevel": {
            "Default": "Information",
            "Override": {
                "Microsoft": "Information",
                "System": "Information"
            }
        }
    },
    "RepositoryName": "my-service",
    "ConnectionStrings": {
        "PersistentStorage": "/persistence"
    }
}

Log files are stored under {PersistentStorage}/{RepositoryName}/{env}/logs/. The LogCleanupHostedService runs every 12 hours and deletes files older than daysToRetain.

Request logging middleware

app.UseRequestLogging();  // logs method, path, status code, elapsed ms, redacted headers/body

Paths under /swagger, /openapi, /above-board, and /favicon.ico are silently skipped. Sensitive header names (auth, token, cookie, pan, cvv, etc.) and matching JSON properties are redacted automatically. Bodies over 16 KB are omitted.

Outbound logging

Captures outbound HttpClient requests with the same redaction rules:

// Register the handler
builder.AddOutboundLoggingHandler();

// Attach to a specific HttpClient
builder.Services
   .AddHttpClient("MyClient", c => c.BaseAddress = new Uri("https://example.com"))
   .AddOutboundLoggingHandler();

Startup logging

builder.LogStartAttempt();   // prints banner to console at startup
app.LogStartSuccess();        // prints success banner with elapsed init time

---

MediatR and FluentValidation

Registers MediatR with a validation pipeline behavior that runs all FluentValidation validators before the handler. Validation failures throw BadRequestException from Pandatech.ResponseCrafter.

Registration

builder.AddMediatrWithBehaviors(AssemblyRegistry.ToArray());

CQRS interfaces

// Commands
public record CreateUserCommand(string Email) : ICommand<UserDto>;
public class CreateUserHandler : ICommandHandler<CreateUserCommand, UserDto> { ... }

// Queries
public record GetUserQuery(Guid Id) : IQuery<UserDto>;
public class GetUserHandler : IQueryHandler<GetUserQuery, UserDto> { ... }

FluentValidation extensions

String validators

RuleFor(x => x.Email).IsEmail();
RuleFor(x => x.Phone).IsPhoneNumber();           // Panda format: (374)91123456
RuleFor(x => x.Contact).IsEmailOrPhoneNumber();
RuleFor(x => x.Payload).IsValidJson();
RuleFor(x => x.Content).IsXssSanitized();

Single file (IFormFile)

RuleFor(x => x.Avatar)
   .HasMaxSizeMb(6)
   .ExtensionIn(".jpg", ".jpeg", ".png");

File collection (IFormFileCollection)

RuleFor(x => x.Docs)
   .MaxCount(10)
   .EachHasMaxSizeMb(10)
   .EachExtensionIn(CommonFileSets.Documents)
   .TotalSizeMaxMb(50);

File presets

CommonFileSets.Images               // .jpg .jpeg .png .webp .heic .heif .svg .avif
CommonFileSets.Documents            // .pdf .txt .csv .json .xml .yaml .md .docx .xlsx .pptx ...
CommonFileSets.ImagesAndAnimations  // Images + .gif
CommonFileSets.ImagesAndDocuments   // Images + Documents
CommonFileSets.ImportFiles          // .csv .xlsx

---

CORS

Development and non-production environments allow all origins. Production restricts to the configured list and automatically adds both www and non-www variants.

Registration

builder.AddCors();
app.UseCors();

Production configuration

{
    "Security": {
        "AllowedCorsOrigins": "https://example.com,https://api.example.com"
    }
}

The list accepts comma- or semicolon-separated URLs. Invalid entries are logged and filtered out.

---

Resilience Pipelines

Built on Polly via Microsoft.Extensions.Http.Resilience. Provides retry, circuit breaker, and timeout policies for HttpClient calls.

Options

1. Global — applies to all registered HttpClients:

builder.AddResilienceDefaultPipeline();

2. Per-client:

builder.Services.AddHttpClient("MyClient")
   .AddResilienceDefaultPipeline();

3. Manual — for wrapping arbitrary async calls:

public class MyService(ResiliencePipelineProvider<string> provider)
{
    public async Task CallAsync()
    {
        var pipeline = provider.GetDefaultPipeline();
        var result = await pipeline.ExecuteAsync(() => _client.GetAsync("/endpoint"));
    }
}

Default pipeline policies

Policy	Configuration
Retry (429)	5 retries, exponential backoff, respects Retry-After
Retry (5xx/408)	7 retries, exponential backoff from 800ms
Circuit breaker	Opens at 50% failure rate over 30 s, min 200 requests
Timeout	8 seconds per attempt

---

Controllers

For applications using classic MVC controllers alongside minimal APIs:

builder.AddControllers(AssemblyRegistry.ToArray());
app.MapControllers();

Controller and action names are automatically kebab-cased (UserProfile → user-profile).

---

SignalR

Local SignalR (single instance):

builder.AddSignalR();

Distributed SignalR backed by Redis (multi-instance):

builder.AddDistributedSignalR("localhost:6379", "app_name");

Both variants include:

• SignalRLoggingHubFilter — logs hub method calls with redacted arguments and elapsed time
• SignalRExceptionFilter — from Pandatech.ResponseCrafter, standardizes error responses
• MessagePack protocol for compact binary serialization

---

OpenTelemetry

builder.AddOpenTelemetry();
app.MapPrometheusExporterEndpoints();

What is included

• ASP.NET Core metrics and traces
• HttpClient metrics and traces
• Entity Framework Core traces
• Runtime metrics
• Prometheus scraping endpoint at /above-board/prometheus
• Health metrics at /above-board/prometheus/health

OTLP export

Set the following in your environment config or as an environment variable to enable OTLP export:

{
    "OTEL_EXPORTER_OTLP_ENDPOINT": "http://localhost:4317"
}

---

Health Checks

builder.AddHealthChecks();

app.EnsureHealthy();           // runs health checks at startup; throws if anything is unhealthy
app.MapHealthCheckEndpoints(); // registers /above-board/ping and /above-board/health

EnsureHealthy skips MassTransit bus checks during startup (those take time to connect). The ping endpoint returns "pong" as plain text. The health endpoint returns the full AspNetCore.HealthChecks.UI JSON format.

Additional health check registrations follow the standard builder.Services.AddHealthChecks().Add...() pattern — the library does not wrap those.

---

Maintenance Mode

Three-mode global switch. Requires Pandatech.DistributedCache to synchronize state across instances.

Mode	Effect
Disabled	Normal operation
EnabledForClients	All routes blocked except /api/admin/* and /hub/admin/*
EnabledForAll	All routes blocked except /above-board/* and OPTIONS preflight

Registration

builder.AddMaintenanceMode();
app.UseMaintenanceMode();       // place before UseResponseCrafter and UseCors

Controlling maintenance mode

Map the built-in endpoint and protect it with your own authorization:

app.MapMaintenanceEndpoint();
// PUT /above-board/maintenance   body: { "mode": 1 }

Or protect with a shared secret query parameter (useful before auth is in place):

app.MapMaintenanceEndpoint(querySecret: "my-secret");
// PUT /above-board/maintenance?secret=my-secret

Programmatic control from application code:

public class AdminService(MaintenanceState state)
{
    public Task EnableMaintenanceAsync(CancellationToken ct)
        => state.SetModeAsync(MaintenanceMode.EnabledForClients, ct);
}

---

Utilities

ValidationHelper

Static regex-based validators with a 50ms timeout per expression.

ValidationHelper.IsEmail("user@example.com");
ValidationHelper.IsUri("https://example.com", allowNonSecure: false);
ValidationHelper.IsGuid("12345678-1234-1234-1234-123456789012");
ValidationHelper.IsPandaFormattedPhoneNumber("(374)91123456");
ValidationHelper.IsArmeniaSocialSecurityNumber("1234567890");
ValidationHelper.IsArmeniaIdCard("123456789");
ValidationHelper.IsArmeniaPassportNumber("AB1234567");
ValidationHelper.IsArmeniaTaxCode("12345678");
ValidationHelper.IsArmeniaStateRegistryNumber("123.456.78901");
ValidationHelper.IsIPv4("192.168.1.1");
ValidationHelper.IsIPv6("2001:db8::1");
ValidationHelper.IsIpAddress("192.168.1.1");
ValidationHelper.IsJson("{\"key\":\"value\"}");
ValidationHelper.IsCreditCardNumber("4111111111111111");
ValidationHelper.IsUsSocialSecurityNumber("123-45-6789");
ValidationHelper.IsUsername("user123");

LanguageIsoCodeHelper

LanguageIsoCodeHelper.IsValidLanguageCode("hy-AM");   // true
LanguageIsoCodeHelper.GetName("hy-AM");                // "Armenian (Armenia)"
LanguageIsoCodeHelper.GetCode("Armenian (Armenia)");   // "hy-AM"

Covers 170+ language-region combinations. The lookup table is initialized once at startup.

PhoneUtil

Normalizes Armenian phone numbers to +374XXXXXXXX format from a variety of input formats:

PhoneUtil.TryFormatArmenianMsisdn("(374)91123456", out var formatted);  // "+37491123456"
PhoneUtil.TryFormatArmenianMsisdn("+374 91 12 34 56", out var formatted); // "+37491123456"
PhoneUtil.TryFormatArmenianMsisdn("091123456", out var formatted);        // "+37491123456"

Returns false and the original input if the number cannot be parsed as an Armenian MSISDN.

UrlBuilder

var url = UrlBuilder.Create("https://api.example.com/users")
   .AddParameter("page", "1")
   .AddParameter("size", "20")
   .Build();
// https://api.example.com/users?page=1&size=20

TimeZone extensions

// Set once at startup from appsettings DefaultTimeZone
builder.MapDefaultTimeZone();

// Convert any DateTime to the configured zone
var local = someUtcDateTime.ToDefaultTimeZone();

IHostEnvironment extensions

env.IsLocal();
env.IsQa();
env.IsLocalOrDevelopment();
env.IsLocalOrDevelopmentOrQa();
env.GetShortEnvironmentName();  // "local" | "dev" | "qa" | "staging" | ""

HttpContext extensions

// Mark a response as private (adds X-Private-Endpoint: 1 header)
context.MarkAsPrivateEndpoint();

Collection extensions

// IEnumerable / IQueryable
var filtered = items.WhereIf(condition, x => x.IsActive);

// In operator
if (status.In(Status.Active, Status.Pending)) { ... }

Dictionary extensions (zero-allocation via CollectionsMarshal)

dict.GetOrAdd(key, defaultValue);
dict.TryUpdate(key, newValue);

JsonConverters

Converter	Behavior
EnumConverterFactory	Accepts enum by name or integer; serializes as name string
CustomDateOnlyConverter	Parses and writes DateOnly in dd-MM-yyyy format

Register via JsonSerializerOptions.Converters or your ResponseCrafter setup.

MethodTimingStatistics

Development-only benchmarking helper. Not for production use (marked with #warning).

var ts = Stopwatch.GetTimestamp();
DoWork();
MethodTimingStatistics.RecordExecution("DoWork", ts);
MethodTimingStatistics.LogAll(logger);

---

PandaVault

builder.ConfigureWithPandaVault();

Loads secrets from PandaVault on all non-Local environments. On Local, the call is a no-op so local appsettings.json is used unchanged.

---

Related Packages

Package	Purpose
Pandatech.ResponseCrafter	Consistent API error responses
Pandatech.DistributedCache	Redis-backed hybrid cache (required for maintenance mode)
Pandatech.Crypto	Cryptographic utilities
Pandatech.FluentMinimalApiMapper	Minimal API endpoint mapping

---

License

MIT