Mastering NullReferenceException Prevention in C#/

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C# 8.0 Nullable References

C# 8.0 Nullable References

Use C# 8.0 nullable references to signal a possible NullReferenceException.

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To prevent a NullReferenceException, we should check and defend against null. The real question is when an object reference might be null and therefore when we should add a null check. That’s precisely what C# 8.0 solves with the nullable references feature.

So far, all references have been nullable by default. But C# 8.0 nullable references change this assumption: all reference variables are now non-nullable by default. This means that when we access the properties or methods of references that might be null, it results in compiler warnings or errors.

This is a big change. Therefore, we need to now turn this feature on at the project level in our .csproj files.

Turning on nullable references

Let’s revisit the example from a previous lesson. This time, let’s turn nullable references on.

C#
<Project Sdk="Microsoft.NET.Sdk">



  <PropertyGroup>

    <OutputType>Exe</OutputType>

    <TargetFramework>net6.0</TargetFramework>

    <!--             ^^^^^^ -->

    <!-- We could use netcoreapp3.1|net5.0|net6.0 too -->

    <ImplicitUsings>enable</ImplicitUsings>

    <Nullable>enable</Nullable>

    <!--      ^^^^^^ -->

    <!-- We could use enable|disable|warning too -->

    <!--<WarningsAsErrors>nullable</WarningsAsErrors>-->

    <!--              ^^^^^^^^ -->

    <!-- We can take the extreme route -->



  </PropertyGroup>



</Project>

To use nullable references, we need to target .NET Core 3.0 and upward. And, in our .csproj files, inside the <Nullable> node, we could use enable, disable, or warning. Unlike enable, which turns on all compiler checks, the warning ...