.NET Documentation

.NET Metadata Tools

.NET provides a rich set of tools and libraries for working with metadata. Metadata in .NET is information that describes the code itself, such as types, members, attributes, and their relationships. Understanding and manipulating this metadata is crucial for advanced development, reflection, serialization, and tooling.

Key Metadata Concepts

• Assemblies: The fundamental unit of deployment, versioning, and security in .NET. Assemblies contain compiled code, resources, and manifest information, including metadata.
• Types: Represent classes, structs, interfaces, enums, and delegates. Metadata describes their members (fields, properties, methods, events).
• Reflection: The ability to inspect and manipulate types and members at runtime. It allows you to discover metadata dynamically.
• Attributes: Special types of metadata that can be applied to code elements to provide declarative information.

Essential Metadata Tools and Libraries

• Reflection API: The cornerstone of metadata manipulation in .NET. Classes like System.Reflection.Assembly, System.Type, and System.Reflection.MemberInfo provide the building blocks for runtime introspection.

  Example: Inspecting Assembly Information

  
  using System;
  using System.Reflection;
  
  public class Program
  {
      public static void Main(string[] args)
      {
          Assembly assembly = typeof(Program).Assembly;
          Console.WriteLine($"Assembly Name: {assembly.GetName().Name}");
          Console.WriteLine($"Version: {assembly.GetName().Version}");
          Console.WriteLine($"Location: {assembly.Location}");
  
          Console.WriteLine("\nTypes defined in this assembly:");
          foreach (Type type in assembly.GetTypes())
          {
              Console.WriteLine($"- {type.FullName}");
          }
      }
  }
                          

• Roslyn API (Microsoft.CodeAnalysis): The .NET Compiler Platform, Roslyn, exposes APIs that allow you to programmatically analyze, manipulate, and even generate C# and Visual Basic code. This is incredibly powerful for building code analysis tools, refactorings, and source generators.

  Example: Simple Syntax Analysis

  
  using Microsoft.CodeAnalysis;
  using Microsoft.CodeAnalysis.CSharp;
  using Microsoft.CodeAnalysis.CSharp.Syntax;
  
  public class RoslynInspector
  {
      public static void AnalyzeCode(string code)
      {
          SyntaxTree tree = CSharpSyntaxTree.ParseText(code);
          var root = tree.GetRoot();
  
          var classDeclarations = root.DescendantNodes().OfType<ClassDeclarationSyntax>();
          Console.WriteLine("Classes found:");
          foreach (var classDecl in classDeclarations)
          {
              Console.WriteLine($"- {classDecl.Identifier.ValueText}");
          }
      }
  }
                          

• IL Disassembler (ildasm.exe): A command-line utility that displays the contents of a Portable Executable (PE) file (like an assembly) in a human-readable format, showing the Intermediate Language (IL) code and metadata. Useful for understanding how code is compiled.
• .NET SDK Tools: The .NET SDK itself includes various command-line tools that leverage metadata, such as:
  • dotnet list package --vulnerable: Analyzes project metadata to identify vulnerable NuGet packages.
  • dotnet publish: Processes assembly metadata for deployment.
• System.Reflection.Emit: Allows you to generate IL code and dynamic assemblies at runtime. This is a more advanced technique for scenarios like creating dynamically generated types or code.

Common Use Cases

• Custom Serialization: Building custom serialization engines that understand type metadata to serialize/deserialize objects.
• Dependency Injection Frameworks: Frameworks like ASP.NET Core's DI container use reflection to discover services and their implementations.
• Object-Relational Mappers (ORMs): ORMs like Entity Framework use metadata to map database tables to .NET types.
• Code Generation: Tools that generate boilerplate code or entire classes based on existing types or definitions.
• Runtime Analysis and Monitoring: Applications that inspect their own runtime state or the state of loaded assemblies.