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dotnet: property declarations

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Lyn Tee
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2 min read

There are multiple ways to declare a property.

Here are different ways, which vary the access level of the setter, from the most protected to the most open:

  • { get; protected init; }

    • Initialising this value can happen only in the class where this is declared, and also in classes that are derived from the base class

    • Once the value is set, it is read only, both internally and externally

  • { get; init; }

    • Any class can initialise and set this value

    • Once the value is set, it is read only, both internally and externally

  • { get; }

    • Read only externally

    • Can be overwritten internally. This is like private(set) in Swift

  • { get; set; }

    • Anything can overwrite the value of this property

With all the above property declarations, you may also need to add = null! at the end of the declaration.

This depends on a few things:

  • the project settings

  • whether the compiler thinks your solution could actually initialise the property and end up with a Null Reference Exception (NRE)

  • whether you are using a value type (e.g. bool) or reference type

    • Value types have a default value. You will never need to add = null! when declaring a value type
<PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
</PropertyGroup>

For example, in the .csproj file, if you include this code snippet, you will need to add =null! to the end of your property declarations.

e.g. public List<string> CakeFlavours { get; set; } = null!;

  • The null! silences the compiler warning. It says to the compiler - trust me, I have coded this correctly and we will never end up in a state where this property is null

  • Be careful - if you do this, and you have a code path which will lead to an NRE, your app will compile and then crash when the NRE happens

C#