Microlens.Proto

Decode and inspect Protocol Buffer (Protobuf) payloads without .proto files, generated classes or schema definitions.

Microlens.Proto is a schemaless Protobuf inspection toolkit for .NET that automatically intercepts, decodes, visualizes and logs Protobuf traffic across HTTP and gRPC boundaries.

Unlike traditional Protobuf libraries that require compile-time contracts, Microlens.Proto works directly against raw wire-format payloads, making it useful for diagnostics, auditing, reverse engineering and production troubleshooting.

Why Microlens.Proto? | Quick Start | Quick Example | Features | Extensible Architecture | Performance Characteristics | Comparison | When Not To Use Microlens.Proto | Articles | License

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Why Microlens.Proto?

Most Protobuf tooling assumes you already have:

• .proto files
• generated C# classes
• source-code access

In many real-world scenarios, you have none of those.

Examples of typical use cases:

• Production Diagnostics: Capture payload structures during incident investigation and troubleshooting.
• Debugging gRPC Requests: inspect request and response messages without modifying service code.
• Auditing Binary Traffic: Understand exactly what is crossing service boundaries.
• Reverse Engineering Legacy Systems: Analyze Protobuf payloads when schemas are unavailable.
• API Discovery: Understand third-party Protobuf protocols without source access.
• Understanding Service Behavior: Analyze what a service is actually sending.

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Quick Start

Installation

dotnet add package Microlens.Proto

Register Services

builder.Services.AddMicrolensProto();

Register Middleware

app.UseMicrolensProto();

That's it.

HTTP and gRPC payload inspection are automatically enabled.

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Quick Example

Given a raw Protobuf payload:

byte[] payload = ...;

Microlens.Proto automatically parses raw Protobuf payloads and converts them into a readable tree structure.

├── Field 1 (Varint): 42
├── Field 2 (LengthDelimited): Device-01
├── Field 3 (LengthDelimited)
│   ├── Field 1 (Varint): 123
│   └── Field 2 (LengthDelimited): Active
└── Field 4 (Fixed64): 987654321

• No .proto files required.
• No schema definitions required.
• No generated classes required.
• No reflection required.
• No custom parsers required.

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Features

Microlens.Proto is NOT intended to replace Google.Protobuf or protobuf-net for serialization and deserialization of known contracts. Instead, it complements them by providing visibility into raw Protobuf traffic.

Schemaless Protobuf Decoding

Decode raw Protobuf wire data without .proto definitions.

Supported wire types:

• Varint
• Fixed32
• Fixed64
• Length Delimited

Nested Message Discovery

Automatically detects and recursively decodes embedded Protobuf messages.

Field 5
├── Field 1: HardwareRev
└── Field 2: v3.2

HTTP Payload Inspection

Intercept outbound and inbound Protobuf traffic automatically.

• HttpClient DelegatingHandler
• ASP.NET Core Middleware

gRPC Message Inspection

Capture and inspect gRPC messages transparently.

• Client Interceptors
• Server Interceptors

Human-Readable Output

Convert binary payloads into readable tree structures.

├── Field 1 (Varint): 999
├── Field 2 (LengthDelimited): Connected
└── Field 3 (Fixed32): 1098488218

JSON Output

Emit structured JSON for:

• Elasticsearch
• Splunk
• OpenSearch
• DataDog
• Custom analytics pipelines

High Performance

Built on:

• ReadOnlySequence<byte>
• Span<T>
• RecyclableMemoryStream

Designed for high-throughput services and production workloads.

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Extensible Architecture

Register:

• Custom formatters
• Custom sinks
• Custom telemetry pipelines

Formatters

Default Formatter

The default formatter generates a human-readable tree structure that can be written directly to your existing logging infrastructure.

TimestampUtc = 2026-06-08T12:00:00Z
Channel = Grpc
Direction = Inbound
Phase = Request
Path = /EnvelopeService/Post

Payload:

├── Field 1 (LengthDelimited): HardwareRev
├── Field 2 (LengthDelimited): v3.2
├── Field 3 (Varint): 42
└── Field 4 (Fixed64): 987654321

Custom Formatters

Microlens.Proto supports custom visualization formats.

Example: Compact Formatter

public sealed class CompactProtoFormatter : IProtoFormatter {
    public ProtoFormatterKey Key => ProtoFormatterKey.Custom;

    public string Name => "Compact";

    public string Format(IReadOnlyList<ProtoNode> nodes) {
        return $"Fields: {nodes.Count}";
    }
}

Register: Compact Formatter

builder.Services.AddFormatter<CompactProtoFormatter>("Compact");

builder.Services.AddMicrolensProto(options => {
    options.FormatterKey = ProtoFormatterKey.Custom;
    options.CustomFormatterName = "Compact";
});

Custom Sinks

Send decoded payload information to any destination.

Example: Serilog Sink

public sealed class SerilogProtoSink : IProtoSink {
    // Custom implementation
}

Register: Serilog Sink

builder.Services.AddSink<SerilogProtoSink>("Serilog");

builder.Services.AddMicrolensProto(options =>
{
    options.SinkKey = ProtoSinkKey.Custom;
    options.CustomSinkName = "Serilog";
});

More Examples:

• Seq
• Elasticsearch
• Splunk
• OpenSearch
• Datadog
• Application Insights
• Custom telemetry platforms

and many more.

What Gets Captured and Logged?

Microlens.Proto can inspect both requests and responses across multiple communication channels.

Channel	Request	Response
HttpClient	✓	✓
ASP.NET Core Middleware	✓	✓
gRPC Client	✓	✓
gRPC Server	✓	✓

Capture and logging behavior can be configured through ProtoOptions.

builder.Services.AddMicrolensProto(options =>
{
    options.CaptureMode = ProtoCaptureMode.Both;
    options.LogScope = ProtoLogScope.Both;
});

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Performance Characteristics

Microlens.Proto is designed for production environments and high-throughput workloads.

Key implementation details:

• ReadOnlySequence<byte> based parsing
• Span<T> friendly processing
• Streaming payload inspection
• Buffer pooling through RecyclableMemoryStream
• Recursive nested message decoding
• Minimal allocations where possible

The library is optimized for observability and diagnostics while minimizing runtime overhead.

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Comparison

Capability	Microlens.Proto	Traditional Protobuf Libraries
Serialize known contracts	Yes	Yes
Deserialize known contracts	Yes	Yes
Schemaless inspection	Yes	Limited
Nested message discovery	Yes	Limited
Works without .proto files	Yes	No
Works without generated classes	Yes	No
Decode unknown Protobuf payloads	Yes	No
HTTP payload interception	Yes	No
gRPC payload interception	Yes	No
Logging integration	Yes	No
Extensible formatters	Yes	No
Extensible sinks	Yes	No

Microlens.Proto focuses on inspection, diagnostics, observability and traffic analysis rather than contract-based serialization.

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When Not To Use Microlens.Proto

Microlens.Proto is not intended for:

• Generating C# classes from .proto files
• Contract-based serialization
• Contract-based deserialization
• Replacing Google.Protobuf
• Replacing protobuf-net

If you already have schema definitions and generated types, use a traditional Protobuf library.

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Articles

• Schemaless Protocol Buffers (Protobuf) Decoder & Inspector — Part 1

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License

Licensed under the Apache License 2.0.

See the LICENSE file for details.

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