URL Pattern Matching in .NET

Working with URLs in .NET applications often involves pattern matching for routing, security policies, or content filtering. While you could write custom regex patterns or string comparisons, there's a better way: the Meziantou.Framework.Uri package brings standardized URL pattern matching to .NET.

This package implements the WHATWG URL Pattern API specification, providing a consistent and powerful way to match URLs against patterns with parameters, wildcards, and modifiers.

#Installation

Install the package via NuGet:

dotnet add package Meziantou.Framework.Uri

#Basic URL Pattern Matching

The package centers on the UrlPattern class, which lets you define patterns and test URLs against them:

var pattern = UrlPattern.Create(new UrlPatternInit
{
    Protocol = "https",
    Hostname = "example.com",
    Pathname = "/books/:id",
});

bool matches = pattern.IsMatch("https://example.com/books/123"); // true

You can also create patterns from a pattern string:

var pattern = UrlPattern.Create("https://example.com/api/:version/*");

#Features

##Wildcards

Use wildcards to match any path or sequence of segments:

var wildcardPattern = UrlPattern.Create(new UrlPatternInit
{
    Pathname = "/files/*",
});

wildcardPattern.IsMatch("https://example.com/files/a/b/c"); // true

##Optional Parameters

Use modifiers to make parts of the pattern optional:

var optionalPattern = UrlPattern.Create(new UrlPatternInit
{
    Pathname = "/items{/:category}?",
});

optionalPattern.IsMatch("https://example.com/items");       // true
optionalPattern.IsMatch("https://example.com/items/books"); // true

##Case-Insensitive Matching

Enable case-insensitive matching with options:

var caseInsensitivePattern = UrlPattern.Create(
    new UrlPatternInit { Pathname = "/Books/:id" },
    new UrlPatternOptions { IgnoreCase = true });

caseInsensitivePattern.IsMatch("https://example.com/BOOKS/123"); // true

##Pattern Collections

Match against multiple patterns and find the first match:

var collection = new UrlPatternCollection
{
    UrlPattern.Create(new UrlPatternInit { Pathname = "/api/*" }),
    UrlPattern.Create(new UrlPatternInit { Pathname = "/docs/*" }),
};

// Test if any pattern matches
bool anyMatch = collection.IsMatch("https://example.com/api/users"); // true

// Get the first matching pattern
UrlPattern? match = collection.FindPattern("https://example.com/docs/guide");

// Match and extract groups
var result = collection.Match("https://example.com/api/v2/users");

#Additional resources

• GitHub repository
• NuGet package
• WHATWG URL Pattern API specification

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