Edkorenkov

var name = Guid.NewGuid()
    .ToString()
    .Aggregate("", (acc, x) =>
    {
        return acc.Length switch
        {
            < 2 when char.IsLetter(x) => $"{acc}{x.ToString().ToUpper()}",
            >= 2 and < 5 when char.IsDigit(x) => $"{acc}{x.ToString()}",
            _ => acc
        };

Edkorenkov

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddControllers();

var app = builder.Build();
    
app
    .UseRouting()
    .UseEndpoints(x => x.MapControllers());
    

Edkorenkov

var retryPolicy = Policy
    .Handle<ApiException>()
    .WaitAndRetryAsync(3, x => TimeSpan.FromSeconds(Math.Pow(2, x)))
    .AsAsyncPolicy<HttpResponseMessage>();

services
    .AddRefitClient<IHttpClient>()
    .ConfigureHttpClient(x => x.BaseAddress = new Uri("https://localhost:8080"))
    .AddPolicyHandler(retryPolicy);

Edkorenkov

// before C#10 and .NET6
//
public void GetSomething(string id)
{
  if (id is null)
  {
    throw new ArgumentNullException(nameof(id));
  }
  
  // ... and here your code to get some data

Edkorenkov

using System;
using System.Web;

public static bool IsValidUri(string input) => Uri.IsWellFormedUriString(input, UriKind.Absolute);

// Input: https://www.youtube.com/watch?v=dfzBMxXQUOc
// Output: dfzBMxXQUOc
static string? GetYouTubeVideoId(string input) 
    => HttpUtility.ParseQueryString(new Uri(input).Query).Get("v");

Edkorenkov

using System.Net;
using System.Linq;

public static bool IsValidIpAddress(string input)
    => IPAddress.TryParse(input, out var ipAddress) && ipAddress.ToString() == input;

public static bool IsValidIpAddress(string input)
    => input.Split(".") switch
    {
        {Length: 4} parts => parts.All(x => int.TryParse(x, out var y) && y is >= 0 and <= 255),