C# 10 Features

using System.Text.Json;
var names = new[] { "Prasad", "Praveen" };
var serialized = JsonSerializer.Serialize(names);
Console.WriteLine(serialized);

var names = new[] { "Prasad", "Praveen" };
var serialized = JsonSerializer.Serialize(names);
Console.WriteLine(serialized);

<PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
</PropertyGroup>
       <ItemGroup Condition="'$(ImplicitUsings)'=='true' Or '$(ImplicitUsings)'== 'enable'">
             <Using Include="System.Text.Json"/>
       </ItemGroup>
</Project>

namespace FileScopedNamespace
{
    internal class Employee
    {
        public string Name { get; set; }
    }
}

namespace FileScopedNamespace
{
    internal class Employee
    {
        public string Name { get; set; }
    }
}
namespace FileScopedNamespace1
{
    internal class Employee1
    {
        public string Name { get; set; }
    }
}

namespace FileScopedNamespace;
internal class Employee
{
    public string Name { get; set; }
}

Constant Interpolated strings

This is another feature which I really like. Assume I have a class like below, I’m trying to apply string interpolation on constant variables.

namespace ConstantInterpolatedString
{
    public static class EmailMessages
    {
        private const string Salutation = "Welcome";
        public static class Header
        {
            public const string SalutionTeamplate = Salutation + " to constant Interpolation";
        }
    }
}

This can be converted into Constant interpolation as below

namespace ConstantInterpolatedString
{
    public static class EmailMessages
    {
        private const string Salutation = "Welcome";
        public static class Header
        {
            public const string SalutionTeamplate = $"{Salutation} to Interpolation";
        }
    }
}

Before C# 10, there was no option to apply interpolation on const variables. It will throw the below compiler error

The expression being assigned to EmailMessages.Header.SalutionTemplate must be constant.

Lambda Improvements

Here we will look at some of the lambda improvements.

Previously, we had a function as below

using System;
Func<string> welcome = () => "Welcome to Lambda Improvements";
Console.WriteLine(welcome);

Here we have a func delegate which returns a string.

Note:

Ensure that our language version is pointing to 9.0 in project file as below

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
       <LangVersion>9.0</LangVersion>
  </PropertyGroup>
</Project>

Now let’s change the syntax of func delegate as below

using System;
var welcome = () => "Welcome to Lambda Improvements";
Console.WriteLine(welcome);

You will get an error as below

Feature ‘inferred delegate type’ is not available in C# 9.0. Please use language version 10.0 or greater.

Now, update the language version in project file and see.

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
       <LangVersion>10.0</LangVersion>
  </PropertyGroup>
</Project>

The code will work as expected.

Next improvement,

Assume that we have the below code

using System;
//var welcome = () => "Welcome to Lambda Improvements";
var text = () => null;
//Console.WriteLine(welcome);

This will raise exception as below

The delegate type could not be inferred

There is an alternative as below

using System;
//var welcome = () => "Welcome to Lambda Improvements";
Func<string?> test  = () => null;
//Console.WriteLine(welcome);

This works fine. However, I want to rewrite this line using var. how? Please see the below syntax

using System;
//var welcome = () => "Welcome to Lambda Improvements";
var text  = string? () => null;
//Console.WriteLine(welcome);

This code will build with zero errors.

Null Parameter Checking

In C # 9.0, we can write the null check as below

string? text = null;
SayHello(text);
void SayHello(string message)
{
    if(message is null)
    {
        throw new ArgumentNullException(nameof(message));
    }
    Console.WriteLine(message);
}

In C# 10.0, we can replace the if condition with below one-liner code

string? text = null;
SayHello(text);
void SayHello(string message)
{
    //if(message is null)
    //{
    //    throw new ArgumentNullException(nameof(message));
    //}
    ArgumentNullException.ThrowIfNull(message);
    Console.WriteLine(message);
}

Thank you for reading my article. I will come up with other features in the upcoming articles. Please provide your feedback in the comment box.