C#リフレクションメモ

reflection.cs

var source = @"
using System;
using System.Collections.Generic;
public class MyRandom
{
public static Dictionary<string, int> GetRandomInt(int maxValue, string sig)
{
    var random = new Random(sig.GetHashCode());
    return new Dictionary<string, int>()
    {
        {sig, random.Next(maxValue + 1)}
    };
}
}";

var options = CSharpParseOptions.Default
    .WithLanguageVersion(LanguageVersion.CSharp8);

var syntaxTree = CSharpSyntaxTree.ParseText(source, options, "MyRandom.cs");

var references = new MetadataReference[]
{
    MetadataReference.CreateFromFile(typeof(object).Assembly.Location),
};
var compilationOptions = new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary);

var compilation = CSharpCompilation.Create(
    "MyRandom.dll",
    new[] { syntaxTree },
    references,
    compilationOptions);

using var stream = new MemoryStream();
var emitResult = compilation.Emit(stream);
if (emitResult.Success)
{
    stream.Seek(0, SeekOrigin.Begin);
    var assembly = AssemblyLoadContext.Default.LoadFromStream(stream);
    var randomType = assembly.GetType("MyRandom");
    //var method = randomType.GetMethod("GetRandomInt");
    var method = randomType.GetMethod("GetRandomInt");
    var result = (Dictionary<string, int>)(method.Invoke(null, new object[]{100, "AAA"}) ?? throw new InvalidOperationException());
    Console.WriteLine($"Add(1, 5) = {result.Keys.FirstOrDefault()} : {result.Values.FirstOrDefault()}");
}
else
{
    IEnumerable<Diagnostic> failures = emitResult.Diagnostics.Where(diagnostic =>
        diagnostic.IsWarningAsError ||
        diagnostic.Severity == DiagnosticSeverity.Error);

    foreach (Diagnostic diagnostic in failures)
    {
        Console.Error.WriteLine("{0}: {1}", diagnostic.Id, diagnostic.GetMessage());
    }
}