A ↑ structure type, or struct type, is a value type that can encapsulate data and related functionality.
You use the struct keyword to define a structure type:
struct A
{
public int X { get; set; }
public int Y { get; set; }
public object O { get; set; }
}Typically, you use structure types to design small data-centric types that provide little or no behavior. For example, .NET uses structure types to represent a number, both integer and real, a Boolean value, a Unicode character, a time instance. If you're focused on the behavior of a type, consider defining a class. Class types have reference semantics. That is, a variable of a class type contains a reference to an instance of the type, not the instance itself.
Because structure types have value semantics, we recommend you to define immutable structure types.
Structures's value types initialized with default values, reference types — with nulls:
A a = new();
Console.WriteLine(a.X); // 0
Console.WriteLine(a.Y); // 0
Console.WriteLine(a.O == null); // TrueBecause structures are value types they are passed by value:
If all instance fields of a structure type are accessible, you can also instantiate it without the new operator. In that case you must initialize all instance fields before the first use of the instance:
A a;
// Compile-time error: "Struct field 'a.X' might not be initialized before accessing"
// Console.WriteLine(a.X);
// Ok
a.X = 1;
a.Y = 2;
struct A
{
public int X;
public int Y;
}The ↑ Span<T> type provides a type-safe and memory-safe representation of a contiguous region of arbitrary memory.
Span<T> is a ↑ ref struct that is allocated on the stack rather than on the managed heap.
A Span<T> instance is often used to hold the elements of an array or a portion of an array. Unlike an array, however, a Span<T> instance can point to managed memory, native memory, or memory managed on the stack.
↑ A brief overview of Span<T>.
↑ A Complete .NET Developer's Guide to Span with Stephen Toub.
Example:
BenchmarkRunner.Run<SpanBenchmark>();
[MemoryDiagnoser]
public class SpanBenchmark
{
private const string DateAsText = "08 07 2021";
[Benchmark]
public (int day, int month, int year) DateWithSubstring()
{
string dayAsText = DateAsText.Substring(0, 2);
string monthAsText = DateAsText.Substring(3, 2);
string yearAsText = DateAsText.Substring(6);
int day = int.Parse(dayAsText);
int month = int.Parse(monthAsText);
int year = int.Parse(yearAsText);
return (day, month, year);
}
[Benchmark]
public (int day, int month, int year) DateWithSpan()
{
ReadOnlySpan<char> dateAsSpan = DateAsText;
ReadOnlySpan<char> dayAsText = dateAsSpan.Slice(0, 2);
ReadOnlySpan<char> monthAsText = dateAsSpan.Slice(3, 2);
ReadOnlySpan<char> yearAsText = dateAsSpan.Slice(6);
int day = int.Parse(dayAsText);
int month = int.Parse(monthAsText);
int year = int.Parse(yearAsText);
return (day, month, year);
}
}Output:
| Method | Mean | Error | StdDev | Median | Gen0 | Allocated |
|------------------ |---------:|---------:|---------:|---------:|-------:|----------:|
| DateWithSubstring | 60.00 ns | 1.217 ns | 2.345 ns | 58.93 ns | 0.0153 | 96 B |
| DateWithSpan | 33.35 ns | 0.506 ns | 0.423 ns | 33.11 ns | - | - |
// * Legends *
Mean : Arithmetic mean of all measurements
Error : Half of 99.9% confidence interval
StdDev : Standard deviation of all measurements
Median : Value separating the higher half of all measurements (50th percentile)
Gen0 : GC Generation 0 collects per 1000 operations
Allocated : Allocated memory per single operation (managed only, inclusive, 1KB = 1024B)
1 ns : 1 Nanosecond (0.000000001 sec)