Add a demo C# program

Author: cgaebel

demo/csharp/.gitignore

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+bin/
+obj/

demo/csharp/Program.cs

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+using System;
+using System.IO;
+
+FileStream r = new FileStream("/dev/zero", FileMode.Open, FileAccess.Read);
+FileStream w = new FileStream("/dev/null", FileMode.Open, FileAccess.Write);
+int len = 4096;
+byte[] buf = new byte[len];
+
+for(;;) {
+	r.Read(buf, 0, len);
+	w.Write(buf, 0, len);
+}

demo/csharp/csharp.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

demo/csharp/run.sh

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+#!/usr/bin/env bash
+COMPlus_PerfMapEnabled=1 dotnet run