StepOne

ConcurrentDictionary<String, SemaphoreSlim>

var vowelSearch = SearchValues.Create(new[] { 'a', 'e', 'i', 'o', 'u' });
var containsVowel = "text".AsSpan().ContainsAny(vowelSearch);

var nameSearch = SearchValues.Create(new[] { "Alice", "Bob", "Charlie", "Diana" }, StringComparison.OrdinalIgnoreCase);
var text = ...
var contains = text.ContainsAny(names);

JsonSerializer.Serialize(MyEnum.Value1 | MyEnum.Value2); // "Value1, Custom enum value"

[Flags, JsonConverter(typeof(JsonStringEnumConverter))]
enum MyEnum
{
    Value1 = 1,
    [JsonStringEnumMemberName("Custom enum value")]
    Value2 = 2,
}

JsonElement left = JsonDocument.Parse("10e-3").RootElement;
JsonElement right = JsonDocument.Parse("0.001").RootElement;
JsonElement.DeepEquals(left, right); // True

JsonSerializerOptions options = new() { AllowOutOfOrderMetadataProperties = true };
JsonSerializer.Deserialize<Base>("""{"Name":"Name","$type":"derived"}""", options); // Success

var guid = Guid.CreateVersion7();
var guidWithTimestamp = Guid.CreateVersion7(DateTimeOffset.UtcNow);

Translate(100m).Should().Be("Сто рублей ноль копеек");

using Nut;

Console.WriteLine(100m.ToText("rub", "ru", new Options { MainUnitFirstCharUpper = true });
// Сто рублей ноль копеек

<Project>
    <PropertyGroup>
        <TargetFramework>net8.0</TargetFramework>
        <ImplicitUsings>enable</ImplicitUsings>
        <Nullable>enable</Nullable>
        <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
    </PropertyGroup>
</Project>

var mockDbConnection = new MockDbConnection();
mockDbConnection.Mocks
    .When(cmd => cmd.CommandText.Contains("count(*) from t1"))
    .ReturnsTable(
        MockTable.WithColumns("Count")
            .AddRow(1));
mockDbConnection.Mocks
    .When(cmd => cmd.CommandText.Contains("count(*) from t2"))
    .ReturnsTable(
        MockTable.WithColumns("Count")
            .AddRow(2));

int[] arr = [];
Console.WriteLine(
    arr.All(x => x % 2 != 0));