For now you can avoid this warning by initializing a _name field using default value with null-forgiving operator !, like private string _name = default!; or private string _name = null!; There is also an open GitHub issue for that. You can also declare the _name as string? and specify that return value of Name … Read more
That’s just the empty property pattern in C# 8, meaning the value not null. It matches any value type or reference type. As Panagiotis Kanavos notes in the comments, this is equivalent to the good old value is object check which has been in C# for a long time. Generally if you were to specify … Read more
What to do if you are using C# 9 In C# 9, you can use T? on an unconstrained type parameter to indicate that the type is always nullable when T is a reference type. In fact, the example in the original question “just works” after adding ? to the property and constructor parameter. See … Read more
It is now possible to treat all nullable-related warnings as errors without explicitly specifying them all. To achieve this, you have to set <WarningsAsErrors>Nullable</WarningsAsErrors> in your *.csproj file [source]. Full example: <Project Sdk=”Microsoft.NET.Sdk.Web”> <PropertyGroup> <TargetFramework>netcoreapp3.1</TargetFramework> <Nullable>enable</Nullable> <WarningsAsErrors>Nullable</WarningsAsErrors> </PropertyGroup> </Project>
You were very close. Just write your method like this: [return: MaybeNull] public T Get<T>(string key) { var wrapper = cacheService.Get(key); return wrapper.HasValue ? Deserialize<T>(wrapper) : default!; } You have to use the default! to get rid of the warning. But you can tell the compiler with [return: MaybeNull] that it should check for null … Read more
You are using C# 8. In older C# versions that ; would have made this invalid. In the new syntax, the client stays in scope for the surrounding method (or other {} scope block). Note that you can omit the outer pair of () as well. It’s called a using declaration, the documentation is here. … Read more
Sure – you just need the ToListAsync() method, which is in the System.Linq.Async NuGet package. Here’s a complete example: Project file: <Project Sdk=”Microsoft.NET.Sdk”> <PropertyGroup> <OutputType>Exe</OutputType> <TargetFramework>netcoreapp3.1</TargetFramework> </PropertyGroup> <ItemGroup> <PackageReference Include=”System.Linq.Async” Version=”4.0.0″ /> </ItemGroup> </Project> Code: using System; using System.Collections.Generic; using System.Linq; using System.Threading.Tasks; class Program { static async Task Main(string[] args) { IAsyncEnumerable<string> sequence = … Read more
This would be the null forgiving operator. It tells the compiler “this isn’t null, trust me”, so it does not issue a warning for a possible null reference. In this particular case it tells the compiler that Entity isn’t null.
Similar as using (…) uses IDisposable to clean up resources, await using (…) uses IAsyncDisposable. This allows to perform also time-consuming tasks (e.g involving I/O) on cleanup without blocking.
In Visual Studio 16.2 (from preview 1) the property name is changed to Nullable, which is simpler and aligns with the command line argument. Add the following properties to your .csproj file. <PropertyGroup> <Nullable>enable</Nullable> <LangVersion>8.0</LangVersion> </PropertyGroup> If you’re targeting netcoreapp3.0 or later, you don’t need to specify a LangVersion to enable nullable reference types. Alternatively, … Read more