public record User(string Name, int Age);

var a = new UserClass("Alice", 25);
var b = new UserClass("Alice", 25);

Console.WriteLine(a == b); // false

var a = new User("Alice", 25);
var b = new User("Alice", 25);

Console.WriteLine(a == b); // true

var user = new User("Alice", 25);

var updated = user with { Age = 26 };

Console.WriteLine(updated);
// User { Name = Alice, Age = 26 }

public record Team(string Name, List<string> Members);

# syntax=docker/dockerfile:1.7

FROM mcr.microsoft.com/dotnet/sdk:9.0 AS build
WORKDIR /src

COPY *.csproj .
RUN --mount=type=cache,target=/root/.nuget/packages \
    dotnet restore

COPY . .
RUN --mount=type=cache,target=/root/.nuget/packages \
    dotnet publish -c Release -o /app

public sealed class ProductConfiguration
    : IEntityTypeConfiguration<Product>
{
    public void Configure(EntityTypeBuilder<Product> builder)
    {
        builder.ToTable("Products", table =>
        {
            table.HasCheckConstraint(
                "CK_Products_Price_Range",
                "[Price] > 0 AND [Price] <= 10000000");
        });

        builder.Property(x => x.Name)
            .HasMaxLength(200)
            .IsRequired();

        builder.Property(x => x.NormalizedName)
            .HasMaxLength(200)
            .IsRequired();

        builder.Property(x => x.Price)
            .HasPrecision(18, 2);

        builder.HasIndex(x => x.NormalizedName)
            .IsUnique()
            .HasDatabaseName("UX_Products_NormalizedName");
    }
}

if (!await db.Products.AnyAsync(x => x.Name == name))
{
    db.Products.Add(product);
    await db.SaveChangesAsync();
}

product.NormalizedName = product.Name
    .Trim()
    .ToUpperInvariant();

dotnet ef migrations add HardenProductSchema

migrationBuilder.DropColumn(
    name: "Name",
    table: "Products");

migrationBuilder.AddColumn<string>(
    name: "DisplayName",
    table: "Products",
    nullable: false);

migrationBuilder.RenameColumn(
    name: "Name",
    table: "Products",
    newName: "DisplayName");

migrationBuilder.AddColumn<string>(
    name: "NormalizedName",
    table: "Products",
    type: "nvarchar(200)",
    nullable: true);

dotnet ef migrations has-pending-model-changes

dotnet ef migrations script \
    --idempotent \
    --output migrations.sql

dotnet ef migrations bundle \
    --self-contained \
    -r linux-x64

unsafe
{
    int* ptr;
}

int number = 42;

int* pointer = &number;

int[] numbers = [10, 20, 30];

fixed (int* first = numbers)
{
    // само закрепление памяти безопасно
}

*pointer;        // dereference
pointer->Value; // доступ через указатель
pointer[0];     // работа с элементами
delegate*<>     // вызов function pointer

private static readonly Dictionary<Type, Metadata> Cache = new();

ConditionalWeakTable<TKey, TValue>

private static readonly ConditionalWeakTable<Type, Metadata> Cache = new();

static Metadata GetMetadata(Type type)
{
    return Cache.GetValue(type, BuildMetadata);
}

static Dictionary<Type, ...>

static ConcurrentDictionary<Type, ...>