a sample C# project that logs timestamped messages to a text file using a custom text logger class.

Logger.cs

using System;
using System.IO;

namespace Logger
{
	public class TextLoggerService
	{
		private readonly string filePath;

		public TextLoggerService()
		{
			string desktopPath = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory);
			string fileName = string.Format("{0}.log", DateTime.Now.ToString("yyyyMMdd"));
			filePath = Path.Combine(desktopPath, fileName);
			if (!File.Exists(filePath))
			{
				using (FileStream fs = File.Create(filePath))
				{
					fs.Close();
				}
			}
		}

		public void LogText(string message)
		{
			string logLine = string.Format("[{0}] {1}{2}", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff"), message, Environment.NewLine);
			using (StreamWriter writer = new StreamWriter(filePath, true))
			{
				writer.Write(logLine);
				writer.Flush();
			}
		}
	}
}

main.cs

using System;
using System.Collections.Generic;
using System.Threading;
using Logger;

namespace MainPackage
{
	public class MainClass
	{
		public static void Main(string[] args)
		{
			TextLoggerService logger = new TextLoggerService();
			Random random = new Random();

			List<string> messages = new List<string>
			{
				"Application Started.",
				"Performing Action 1.",
				"Performing Action 2.",
				"Performing Action 3.",
				"Performing Action 4.",
				"Performing Action 5.",
				"Saving Collected Results.",
				"Application Ended."
			};

			foreach (string message in messages)
			{
				Console.WriteLine(message);
				logger.LogText(message);
				Thread.Sleep(random.Next(500, 3000));
			}
		}
	}
}

main.csproj

<?xml version="1.0" encoding="utf-8"?>
<Project
	xmlns="http://schemas.microsoft.com/developer/msbuild/2003"
	Sdk="Microsoft.NET.Sdk"
	DefaultTargets="Build"
>
	<PropertyGroup>
		<AssemblyName>main</AssemblyName>
		<OutputPath>bin\</OutputPath>
	</PropertyGroup>

	<ItemGroup>
		<Compile Include="main.cs" />
		<Compile Include="Logger.cs" />
	</ItemGroup>

	<Target Name="Build" Inputs="@(Compile)" Outputs="$(OutputPath)$(AssemblyName).exe">
		<MakeDir Directories="$(OutputPath)" Condition="!Exists('$(OutputPath)')" />
		<Csc Sources="@(Compile)" OutputAssembly="$(OutputPath)$(AssemblyName).exe">
			<Output TaskParameter="OutputAssembly" ItemName="OutputFile" />
		</Csc>
		<Message Text="Generated file: @(OutputFile)" Condition="Exists('@(OutputFile)')" />
	</Target>

	<Target Name="Clean" >
		<Delete Files="$(OutputPath)$(AssemblyName).exe" />
	</Target>

	<Target Name="Rebuild" DependsOnTargets="Clean;Build" />
</Project>