Applying C# code formatting using EditorConfig, dotnet format, Git pre-commit and Azure Pipelines

24 July 22

Have you ever worked on a project and found your own coding style differs from either the company's or another developer's style preferences? Having a consistent style applied cuts out the time we might otherwise spend stumbling over the style preferences of others

EditorConfig

A .editorconfig file is used to set rules that are then interpreted by plugins to maintain consistent coding styles for all developers working on a project regardless of the tools they are using to write code. See more at https://editorconfig.org

In a C# application, a .editorconfig file can be placed in each individual project's directory to allow us to specify rules per project or at a higher level directory such as where the solution file lives so that it is used across all projects in the solution. Microsoft guidance on .NET code style rule options can be found at https://docs.microsoft.com/en-us/dotnet/fundamentals/code-analysis/code-style-rule-options

It's worth spending some time reading into EditorConfig rules to understand their interpretation and discuss preferences with your team. For this example, we'll use the .NET Team's .editorconfig found at https://github.com/dotnet/runtime/blob/main/.editorconfig

# editorconfig.org

# top-most EditorConfig file
root = true

# Default settings:
# A newline ending every file
# Use 4 spaces as indentation
[*]
insert_final_newline = true
indent_style = space
indent_size = 4
trim_trailing_whitespace = true

# Generated code
[*{_AssemblyInfo.cs,.notsupported.cs,AsmOffsets.cs}]
generated_code = true

# C# files
[*.cs]
# New line preferences
csharp_new_line_before_open_brace = all
csharp_new_line_before_else = true
csharp_new_line_before_catch = true
csharp_new_line_before_finally = true
csharp_new_line_before_members_in_object_initializers = true
csharp_new_line_before_members_in_anonymous_types = true
csharp_new_line_between_query_expression_clauses = true

# Indentation preferences
csharp_indent_block_contents = true
csharp_indent_braces = false
csharp_indent_case_contents = true
csharp_indent_case_contents_when_block = true
csharp_indent_switch_labels = true
csharp_indent_labels = one_less_than_current

# Modifier preferences
csharp_preferred_modifier_order = public,private,protected,internal,static,extern,new,virtual,abstract,sealed,override,readonly,unsafe,volatile,async:suggestion

# avoid this. unless absolutely necessary
dotnet_style_qualification_for_field = false:suggestion
dotnet_style_qualification_for_property = false:suggestion
dotnet_style_qualification_for_method = false:suggestion
dotnet_style_qualification_for_event = false:suggestion

# Types: use keywords instead of BCL types, and permit var only when the type is clear
csharp_style_var_for_built_in_types = false:suggestion
csharp_style_var_when_type_is_apparent = false:none
csharp_style_var_elsewhere = false:suggestion
dotnet_style_predefined_type_for_locals_parameters_members = true:suggestion
dotnet_style_predefined_type_for_member_access = true:suggestion

# name all constant fields using PascalCase
dotnet_naming_rule.constant_fields_should_be_pascal_case.severity = suggestion
dotnet_naming_rule.constant_fields_should_be_pascal_case.symbols  = constant_fields
dotnet_naming_rule.constant_fields_should_be_pascal_case.style    = pascal_case_style
dotnet_naming_symbols.constant_fields.applicable_kinds   = field
dotnet_naming_symbols.constant_fields.required_modifiers = const
dotnet_naming_style.pascal_case_style.capitalization = pascal_case

# static fields should have s_ prefix
dotnet_naming_rule.static_fields_should_have_prefix.severity = suggestion
dotnet_naming_rule.static_fields_should_have_prefix.symbols  = static_fields
dotnet_naming_rule.static_fields_should_have_prefix.style    = static_prefix_style
dotnet_naming_symbols.static_fields.applicable_kinds   = field
dotnet_naming_symbols.static_fields.required_modifiers = static
dotnet_naming_symbols.static_fields.applicable_accessibilities = private, internal, private_protected
dotnet_naming_style.static_prefix_style.required_prefix = s_
dotnet_naming_style.static_prefix_style.capitalization = camel_case

# internal and private fields should be _camelCase
dotnet_naming_rule.camel_case_for_private_internal_fields.severity = suggestion
dotnet_naming_rule.camel_case_for_private_internal_fields.symbols  = private_internal_fields
dotnet_naming_rule.camel_case_for_private_internal_fields.style    = camel_case_underscore_style
dotnet_naming_symbols.private_internal_fields.applicable_kinds = field
dotnet_naming_symbols.private_internal_fields.applicable_accessibilities = private, internal
dotnet_naming_style.camel_case_underscore_style.required_prefix = _
dotnet_naming_style.camel_case_underscore_style.capitalization = camel_case

# Code style defaults
csharp_using_directive_placement = outside_namespace:suggestion
dotnet_sort_system_directives_first = true
csharp_prefer_braces = true:silent
csharp_preserve_single_line_blocks = true:none
csharp_preserve_single_line_statements = false:none
csharp_prefer_static_local_function = true:suggestion
csharp_prefer_simple_using_statement = false:none
csharp_style_prefer_switch_expression = true:suggestion
dotnet_style_readonly_field = true:suggestion

# Expression-level preferences
dotnet_style_object_initializer = true:suggestion
dotnet_style_collection_initializer = true:suggestion
dotnet_style_explicit_tuple_names = true:suggestion
dotnet_style_coalesce_expression = true:suggestion
dotnet_style_null_propagation = true:suggestion
dotnet_style_prefer_is_null_check_over_reference_equality_method = true:suggestion
dotnet_style_prefer_inferred_tuple_names = true:suggestion
dotnet_style_prefer_inferred_anonymous_type_member_names = true:suggestion
dotnet_style_prefer_auto_properties = true:suggestion
dotnet_style_prefer_conditional_expression_over_assignment = true:silent
dotnet_style_prefer_conditional_expression_over_return = true:silent
csharp_prefer_simple_default_expression = true:suggestion

# Expression-bodied members
csharp_style_expression_bodied_methods = true:silent
csharp_style_expression_bodied_constructors = true:silent
csharp_style_expression_bodied_operators = true:silent
csharp_style_expression_bodied_properties = true:silent
csharp_style_expression_bodied_indexers = true:silent
csharp_style_expression_bodied_accessors = true:silent
csharp_style_expression_bodied_lambdas = true:silent
csharp_style_expression_bodied_local_functions = true:silent

# Pattern matching
csharp_style_pattern_matching_over_is_with_cast_check = true:suggestion
csharp_style_pattern_matching_over_as_with_null_check = true:suggestion
csharp_style_inlined_variable_declaration = true:suggestion

# Null checking preferences
csharp_style_throw_expression = true:suggestion
csharp_style_conditional_delegate_call = true:suggestion

# Other features
csharp_style_prefer_index_operator = false:none
csharp_style_prefer_range_operator = false:none
csharp_style_pattern_local_over_anonymous_function = false:none

# Space preferences
csharp_space_after_cast = false
csharp_space_after_colon_in_inheritance_clause = true
csharp_space_after_comma = true
csharp_space_after_dot = false
csharp_space_after_keywords_in_control_flow_statements = true
csharp_space_after_semicolon_in_for_statement = true
csharp_space_around_binary_operators = before_and_after
csharp_space_around_declaration_statements = do_not_ignore
csharp_space_before_colon_in_inheritance_clause = true
csharp_space_before_comma = false
csharp_space_before_dot = false
csharp_space_before_open_square_brackets = false
csharp_space_before_semicolon_in_for_statement = false
csharp_space_between_empty_square_brackets = false
csharp_space_between_method_call_empty_parameter_list_parentheses = false
csharp_space_between_method_call_name_and_opening_parenthesis = false
csharp_space_between_method_call_parameter_list_parentheses = false
csharp_space_between_method_declaration_empty_parameter_list_parentheses = false
csharp_space_between_method_declaration_name_and_open_parenthesis = false
csharp_space_between_method_declaration_parameter_list_parentheses = false
csharp_space_between_parentheses = false
csharp_space_between_square_brackets = false

# License header
file_header_template = Licensed to the .NET Foundation under one or more agreements.\nThe .NET Foundation licenses this file to you under the MIT license.

# C++ Files
[*.{cpp,h,in}]
curly_bracket_next_line = true
indent_brace_style = Allman

# Xml project files
[*.{csproj,vbproj,vcxproj,vcxproj.filters,proj,nativeproj,locproj}]
indent_size = 2

[*.{csproj,vbproj,proj,nativeproj,locproj}]
charset = utf-8

# Xml build files
[*.builds]
indent_size = 2

# Xml files
[*.{xml,stylecop,resx,ruleset}]
indent_size = 2

# Xml config files
[*.{props,targets,config,nuspec}]
indent_size = 2

# YAML config files
[*.{yml,yaml}]
indent_size = 2

# Shell scripts
[*.sh]
end_of_line = lf
[*.{cmd,bat}]
end_of_line = crlf

Create a .editorconfig file in your solution or project directory that contains these settings

Note: this contains a file_header_template rule that if applied as-is will add .NET Foundation license text into each of your files. This should be modified or removed as required

dotnet-format

Part of the .NET 6 SDK, dotnet-format is a code formatter that can be used to apply a core set of EditorConfig options and the .NET coding convention settings for EditorConfig. More at https://github.com/dotnet/format

The dotnet format command can be ran from your project directory and will use the .editorconfig file either in the current directory or a directory above if it exists there. This is useful but let's go a step further and ensure the command is ran as part of the pre-commit

pre-commit

Assuming you are using Git, create a pre-commit file inside your application's .git/hooks directory with the contents below, taken from https://github.com/dotnet/format/blob/main/docs/integrations.md#pre-commitcom-hook-to-reformat

#!/bin/sh
LC_ALL=C
# Select files to format
FILES=$(git diff --cached --name-only --diff-filter=ACM "*.cs" | sed 's| |\\ |g')
[ -z "$FILES" ] && exit 0

# Format all selected files
echo "$FILES" | cat | xargs | sed -e 's/ /,/g' | xargs dotnet format --include

# Add back the modified files to staging
echo "$FILES" | xargs git add

exit 0

Great, so now even if we forget to run dotnet format it will be ran when we commit our code. This however depends on each developer having the hook in their workspace which may not be the case if excluded from version control. Let's go one step further and ensure the code being committed follows the style rules when the code is built

Azure Pipelines

For projects that use a azure-pipelines.yml or equivalent, a task can be added to run dotnet format to verify there are no differences in style with the incoming code

- task: DotNetCoreCLI@2
    displayName: 'dotnet-format'
    inputs:
      command: 'custom'
      custom: 'format'
      arguments: '--verify-no-changes'
      projects: '**/*.csproj'

Again, great. We now have our preferred styles defined in .editorconfig, a pre-commit hook applying them with dotnet format and out build pipeline ensuring the code that has been committed follows the styles as intended