Langversion Latest

[Mireille Kreines]

WhenCheckForOverflowUnderflow is true, the default context is a checked context and overflow checking is enabled; otherwise, the default context is an unchecked context. The default value for this option is false, that is, overflow checking is disabled.

This option specifies the names of one or more symbols that you want to define. The DefineConstants option has the same effect as the #define preprocessor directive except that the compiler option is in effect for all files in the project. A symbol remains defined in a source file until an #undef directive in the source file removes the definition. When you use the -define option, an #undef directive in one file has no effect on other source code files in the project. You can use symbols created by this option with #if, #else, #elif, and #endif to compile source files conditionally. The C# compiler itself defines no symbols or macros that you can use in your source code; all symbol definitions must be user-defined.

The default language version for the C# compiler depends on the target framework for your application and the version of the SDK or Visual Studio installed. Those rules are defined in C# language versioning.

To ensure that your project uses the default compiler version recommended for your target framework, don't use the LangVersion option. You can update the target framework to access newer language features.

Specifying LangVersion with the default value is different from omitting the LangVersion option. Specifying default uses the latest version of the language that the compiler supports, without taking into account the target framework. For example, building a project that targets .NET 6 from Visual Studio version 17.6 uses C# 10 if LangVersion isn't specified, but uses C# 11 if LangVersion is set to default.

Because each version of the C# compiler contains extensions to the language specification, LangVersion doesn't give you the equivalent functionality of an earlier version of the compiler.

While C# version updates generally coincide with major .NET releases, the new syntax and features aren't necessarily tied to that specific framework version. Each specific feature has its own minimum .NET API or common language runtime requirements that may allow it to run on downlevel frameworks by including NuGet packages or other libraries.

Regardless of which LangVersion setting you use, use the current version of the common language runtime to create your .exe or .dll. One exception is friend assemblies and ModuleAssemblyName, which work under -langversion:ISO-1.

The argument must be one of enable, disable, warnings, or annotations. The enable argument enables the nullable context. Specifying disable will disable the nullable context. When you specify the warnings argument, the nullable warning context is enabled. When you specify the annotations argument, the nullable annotation context is enabled. The values are described and explained in the article on Nullable contexts. You can learn more about the tasks involved in enabling nullable reference types in an existing codebase in our article on nullable migration strategies.

Flow analysis is used to infer the nullability of variables within executable code. The inferred nullability of a variable is independent of the variable's declared nullability. Method calls are analyzed even when they're conditionally omitted. For instance, Debug.Assert in release mode.

The global nullable context does not apply for generated code files. Regardless of this setting, the nullable context is disabled for any source file marked as generated. There are four ways a file is marked as generated:

Recently our development team decided to use C# 7.1 language features. However our builds on Azure DevOps started failing quickly. In this quick post we will see how to build your solution targeting the latest version of C# on Azure DevOps.

The issue was that our agent machines have Visual Studio 2017 v15.9.14 installed and by default it targets major version of C#. This can be confirmed by running below command in Developer Command Prompt.

We can resolve this error by explicitly instructing the compiler that we would like to use the latest version of the language. Microsoft documentation provides 3 options to override and build your application using required language version.

If you do not want to edit your project file, you can still fix the build by passing -langversion:latest compiler option in the build pipeline in Azure DevOps. For this, go edit the pipeline and under Visual Studio Build task pass the option under MSBuild Arguments section as below.

In this blog post we saw how we can set and use the latest version version of C# when building .NET Core applications. We also saw how we can pass compiler option in Azure DevOps Visual Studio build step if team has already agreed to use the latest version of the C# language.

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