C# Formatter

How the C# formatter works

The engine is CSharpier (WASM), an opinionated formatter for C# that parses with Roslyn, the same compiler front end Visual Studio and dotnet build use. Because the parse is real, anything modern C# allows is understood: records, file-scoped namespaces, top-level statements, pattern matching, switch expressions, raw string literals and primary constructors.

CSharpier deliberately has very few settings. It decides where lines break based on the line width, and it always produces the same output for the same input, which is what makes it useful in code review: two developers formatting the same file can never disagree. Typical changes include:

• Allman-style braces, each on its own line
• a blank line between class members
• using directives sorted, with System namespaces first
• long LINQ chains broken before each .Where, .Select or .OrderBy
• trailing commas added to multi-line switch expressions and initializers

Settings and keyboard shortcuts

C# has no extra switches on this page. The indent and line-width controls in the toolbar are passed to CSharpier as indentSize/useTabs and printWidth. Note the mismatch with .NET conventions: CSharpier and Visual Studio default to 4-space indentation and a width of 100, whereas the toolbar starts at 2 and 80. Change both if you are tidying code that will be committed to a repository that already uses CSharpier or dotnet format.

Ctrl/Cmd+Enter reformats, Ctrl/Cmd+Shift+C puts the result on the clipboard, and Ctrl/Cmd+K opens the command palette to switch to another language. C# is not a format that can be minified, so Ctrl/Cmd+Shift+M has nothing to do here.

Things worth knowing

CSharpier is a layout tool, not an analyser. It will not rename variables, add var, remove unused usings or apply .editorconfig code-style rules; that is the job of dotnet format or your IDE. It also does not resolve types, so a snippet that references classes you did not paste formats without complaint.

When the input does not compile at the syntax level you get Roslyn’s error code and text, for example CS1002: ; expected. The two numbers in parentheses before the code are the line and column, which is the quickest way to find the problem in a long file.

To protect a hand-aligned block, such as a lookup table, put // csharpier-ignore on the line above it, or wrap a region in // csharpier-ignore-start and // csharpier-ignore-end. Comments, #region markers and XML doc comments are kept.

Razor (.cshtml) and XAML are different languages and are not handled here; for project files such as .csproj use the XML formatter.

Examples

public static class Pricing{public static decimal Discount(Customer c,decimal total)=>c switch{{IsVip:true}when total>500=>total*0.15m,{IsVip:true}=>total*0.1m,_=>0m};}
public record Customer(string Name,bool IsVip);

public static class Pricing
{
    public static decimal Discount(Customer c, decimal total) =>
        c switch
        {
            { IsVip: true } when total > 500 => total * 0.15m,
            { IsVip: true } => total * 0.1m,
            _ => 0m,
        };
}

public record Customer(string Name, bool IsVip);

var builder=WebApplication.CreateBuilder(args);var app=builder.Build();app.MapGet("/orders/{id:int}",async(int id,ShopDb db)=>await db.Orders.FindAsync(id) is Order o?Results.Ok(o):Results.NotFound());app.Run();

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();
app.MapGet(
    "/orders/{id:int}",
    async (int id, ShopDb db) =>
        await db.Orders.FindAsync(id) is Order o
            ? Results.Ok(o)
            : Results.NotFound()
);
app.Run();

public class OrderQueries{private readonly ShopDb _db;public OrderQueries(ShopDb db)=>_db=db;public async Task<List<OrderDto>> RecentAsync(int days,CancellationToken ct){var since=DateTime.UtcNow.AddDays(-days);return await _db.Orders.Where(o=>o.Created>=since&&o.Status==Status.Paid).OrderByDescending(o=>o.Created).Select(o=>new OrderDto(o.Id,o.Total)).ToListAsync(ct);}}

public class OrderQueries
{
    private readonly ShopDb _db;

    public OrderQueries(ShopDb db) => _db = db;

    public async Task<List<OrderDto>> RecentAsync(int days, CancellationToken ct)
    {
        var since = DateTime.UtcNow.AddDays(-days);
        return await _db
            .Orders.Where(o => o.Created >= since && o.Status == Status.Paid)
            .OrderByDescending(o => o.Created)
            .Select(o => new OrderDto(o.Id, o.Total))
            .ToListAsync(ct);
    }
}

Common errors and how to fix them

Related tools

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