c#-7.0 – Tarik Billa

Return multiple values from a C# asynchronous method

April 3, 2024 by Tarik

After playing with the code I was able to figure it out. Here is the solution. public async Task DeleteSchoolTask(int schoolNumber, int taskDetailId) { var result = await GetTaskTypeAndId(taskDetailId); int taskId = result.Item1; string taskType = result.Item2; // step 1: delete attachment physically from server var fileService = new FileService(Logger, CurrentUser); var relativeFilePath = $”{schoolNumber}\\{Consts.RM_SCHOOL}\\{taskDetailId}”; … Read more

What’s the benefit of var patterns in C#7?

January 8, 2024 by Tarik

The var pattern was very frequently discussed in the C# language repository given that it’s not perfectly clear what its use case is and given the fact that is var x does not perform a null check while is T x does, making it appear rather useless. However, it is actually not meant to be … Read more

Using a C# 7 tuple in an ASP.NET Core Web API Controller

January 4, 2024 by Tarik

It doesn’t work because named tuple names are not quite “real”, it’s mostly syntax sugar provided by compiler. If you look at ValueTuple set of types, by which named tuples are represented, you will see that they have properties like Item1, Item2 and so on. Compiler will rewrite all your references to named tuple names … Read more

How to declare a C# Record Type?

January 2, 2024 by Tarik

Update: C# 9 now contains record types. public record Person { public string LastName { get; } public string FirstName { get; } public Person(string first, string last) => (FirstName, LastName) = (first, last); } Old answer: Record types are not (yet) implemented in C#. See the proposal in the official GitHub repository: https://github.com/dotnet/csharplang/blob/master/proposals/records.md Discuss … Read more

Using named tuples in select statements

December 22, 2023 by Tarik

You can just use var, but you need to make sure the tuple elements are actually named. In C# 7.0, you need to do this explicitly: var tuples = source.Select(x => (A: x.A, B: x.B)); foreach (var tuple in tuples) { Console.WriteLine($”{tuple.A} / {tuple.B}”); } In C# 7.1, when the value in a tuple literal … Read more

C# 7.0 ValueTuples vs Anonymous Types

December 16, 2023 by Tarik

Anonymous types are immutable, ValueTuples are not. This is reflected in the fact that anonymous types expose properties, ValueTuples expose fields. Data binding almost always requires properties. Plenty of existing code only works with reference types, not with value types. What in particular comes to mind are projections in Entity Framework: projections to value types … Read more

Name ValueTuple properties when creating with new

December 16, 2023 by Tarik

No, you can’t. The ValueTuple types are actually independent of the named field support in C#. The latter works more like named properties for anonymous types. That is, the compiler analyzes the code and generates aliases to the appropriate members according to your declarations and usages. It is through the assignment that the compiler learns … Read more

Does C# 7 allow to deconstruct tuples in linq expressions

December 16, 2023 by Tarik

It seems not. There’s an open issue for this on GitHub: https://github.com/dotnet/roslyn/issues/6877 Edit Issue moved to dotnet/csharplang#355

C# 7 ValueTuple compile error

December 4, 2023 by Tarik

If anyone falls in the same trap, to fix this you need to update this package: Microsoft.Net.Compilers to 2.0 (you need to show pre-release)

C# 7 Expression Bodied Constructors

December 1, 2023 by Tarik

A way to do this is to use a tuple and a deconstruction to allow multiple assignments in one expression: public class Person { public string Name { get; } public int Age { get; } public Person(string name, int age) => (Name, Age) = (name, age); } As of C# 7.1 (introduced with Visual … Read more