For issues relating to development with C#, version 7.3. In most cases you should also specify the c# tag.
C# 7.3 is a version of the c# programming language. It ships with the 15.7 release of Visual Studio 2017.
Questions tagged [c#-7.3]
86 questions
68
votes
15 answers
VS Code CSC : error CS1617: Invalid option '7.3' for /langversion
I downloaded VS 2017 15.7, .NET Core 2.1.2 and Blazor to try it out. It wasn't working in VS 2017 properly
and thought I would try through the dotnet cli and VS Code. Instead I was met with the following error:
CSC : error CS1617: Invalid option…
Spydernaz
- 847
- 2
- 8
- 14
64
votes
2 answers
C# 7.3 Enum constraint: Why can't I use the nullable enum?
Now that we have enum constraint, why doesn't compiler allow me to write this code?
public static TResult? ToEnum(this String value, TResult? defaultValue)
where TResult : Enum
{
return String.IsNullOrEmpty(value) ? defaultValue :…
Kirill Kovalenko
- 2,121
- 16
- 18
28
votes
1 answer
C# 7.3 Enum constraint: Why can't I use the enum keyword?
To constrain a generic type parameter to be of an enum type, I previously constrained them like this, which was the best I could go for constraining type T for enums in pre-C# 7.3:
void DoSomething() where T : struct, IComparable, IConvertible,…
Ray
- 7,940
- 7
- 58
- 90
25
votes
4 answers
Equality and polymorphism
With two immutable classes Base and Derived (which derives from Base) I want to define Equality so that
equality is always polymorphic - that is ((Base)derived1).Equals((Base)derived2) will call Derived.Equals
operators == and != will call Equals…
kofifus
- 17,260
- 17
- 99
- 173
15
votes
1 answer
Deconstruction is ambiguous
I have a vector class with two deconstruction methods as follows:
public readonly struct Vector2
{
public readonly double X, Y;
...
public void Deconstruct( out double x, out double y )
{
x = this.X;
y = this.Y;
…
Chris
- 5,442
- 17
- 30
15
votes
1 answer
Why is a generic type constrained by 'Enum' failing to qualify as a 'struct' in C# 7.3?
If I have a generic interface with a struct constraint like this:
public interface IStruct where T : struct { }
I can supply an enumeration as my type T like so, because an enum satisfies a struct constraint:
public class EnumIsAStruct :…
Stephen Kennedy
- 20,585
- 22
- 95
- 108
14
votes
1 answer
How is it that a struct containing ValueTuple can satisfy unmanaged constraints, but ValueTuple itself cannot?
Consider the following types:
(int, int) → managed.
struct MyStruct { public (int,int) Value; } → unmanaged!
Problem: A non-generic structure MyStruct, which has a managed member (int,int) has been evaluated as managed type.
Expected Behavior: A…
Reza Aghaei
- 120,393
- 18
- 203
- 398
13
votes
2 answers
How do I check if a type fits the unmanaged constraint in C#?
How do I check if a type T fits the unmanaged type constraint, such that it could be used in a context like this: class Foo where T : unmanaged? My first idea was typeof(T).IsUnmanaged or something similar, but that isn't a property/field of the…
John
- 598
- 2
- 7
- 22
12
votes
1 answer
Implicit static constructor called before Main()
I have the following piece of codes.
class Program
{
static void Main(string[] args)
{
Enterprise.Initialize("Awesome Company");
// Assertion failed when constructor of 'Reg' class is disabled.
Debug.Assert(Reg.Root…
Noctis Tong
- 459
- 1
- 7
- 17
10
votes
1 answer
Struct pointer (address), and default constructor
Does taking address of a C# struct cause default constructor call?
For example, I got such structs:
[StructLayout(LayoutKind.Sequential, Pack = 1)]
public struct HEADER {
public byte OPCODE;
public byte…
lisz
- 435
- 5
- 9
10
votes
1 answer
Is a Span pointing to Fixed Sized Buffers without a fixed expression possible?
I'm using .NET Core 2.1 and language standard 7.3. I wish to reference a fixed buffer without obtaining a pointer to it. Is it currently possible?
public unsafe struct InteropStruct
{
private fixed byte dataField[32];
public Span…
Gamma_Draconis
- 179
- 1
- 11
9
votes
1 answer
Can I use C# 7.3 with .Net Framework 4.6.1?
I'm interested in enum generic constraints, but when I'm switching language version for project on Build → Advanced I'm still getting error «not available in C#5; please use language version 7.3 or greater» even after reopening the project.
Project…
Troll the Legacy
- 675
- 2
- 7
- 22
9
votes
1 answer
Why can a full property in C# be overridden with only a getter but it can still be set?
I came across a behavior that surprises me. Given the following two classes:
class Parent
{
public virtual bool Property { get; set; }
}
class Child : Parent
{
public override bool Property { get => base.Property; }
}
I can write code…
rory.ap
- 34,009
- 10
- 83
- 174
8
votes
1 answer
Writing byte array to Span and sending it with Memory
I am receiving a buffer and i want from it to create a new buffer ( concatenating bytes prefixed,infixed and postfixed) and send it later on to a socket.
Eg:
Initial buffer: "aaaa"
Final buffer: "$4\r\naaaa\r\n" (Redis RESP Protocol - Bulk…
Bercovici Adrian
- 8,794
- 17
- 73
- 152
7
votes
1 answer
Why can ValueTuple not be const?
ValueTuple types, declared as fields, can be mutable:
class Foo {
(int, int) bar = (0, 1);
}
or readonly:
class Foo {
readonly (int, int) bar = (0, 1);
}
and this (im)mutability applies to each member. I would expect it to be stretched to…
Alex Butenko
- 3,664
- 3
- 35
- 54