Bits of .NET

🎯 Pattern Matching = Cleaner Code

Complex conditionals are hard to read. Pattern matching makes code more expressive and maintainable.

📝 Pattern Matching Basics

// Type Patterns
public void ProcessShape(object shape)
{
    if (shape is Circle circle)
    {
        Console.WriteLine($"Circle with radius {circle.Radius}");
    }
    else if (shape is Rectangle rect)
    {
        Console.WriteLine($"Rectangle {rect.Width}x{rect.Height}");
    }
    else if (shape is Triangle tri)
    {
        Console.WriteLine($"Triangle with sides {tri.SideA}, {tri.SideB}, {tri.SideC}");
    }
}

// Switch Expression (C# 8+)
public string GetShapeInfo(object shape) => shape switch
{
    Circle { Radius: > 10 } => "Large circle",
    Circle { Radius: > 5 } => "Medium circle",
    Circle { Radius: <= 5 } => "Small circle",
    Rectangle { Width: var w, Height: var h } when w == h => $"Square ({w}x{h})",
    Rectangle { Width: var w, Height: var h } => $"Rectangle ({w}x{h})",
    Triangle { SideA: var a, SideB: var b, SideC: var c } => $"Triangle ({a},{b},{c})",
    null => "Null object",
    _ => "Unknown shape"
};

// Property Patterns
public bool IsValidUser(User user) => user is
{
    Age: > 18,
    Email: not null,
    Status: UserStatus.Active
};

🎯 Advanced Pattern Matching

// Tuple Patterns
public string EvaluateState(bool isActive, bool isVerified) => (isActive, isVerified) switch
{
    (true, true) => "Fully active",
    (true, false) => "Active but unverified",
    (false, true) => "Verified but inactive",
    (false, false) => "Inactive and unverified"
};

// Relational Patterns (C# 9+)
public string GetTemperatureCategory(int temperature) => temperature switch
{
    < 0 => "Freezing",
    < 10 => "Cold",
    < 20 => "Cool",
    < 30 => "Warm",
    < 40 => "Hot",
    >= 40 => "Very hot"
};

// Logical Patterns
public string GetStudentGrade(int score) => score switch
{
    >= 90 and <= 100 => "A",
    >= 80 and < 90 => "B",
    >= 70 and < 80 => "C",
    >= 60 and < 70 => "D",
    < 60 => "F",
    _ => "Invalid score"
};

// Positional Patterns
public record Point(int X, int Y);

public string DescribePoint(Point point) => point switch
{
    (0, 0) => "Origin",
    (var x, 0) => $"On X-axis at {x}",
    (0, var y) => $"On Y-axis at {y}",
    (var x, var y) when x == y => $"On diagonal at ({x},{y})",
    (var x, var y) => $"At ({x},{y})"
};

// List Patterns (C# 11+)
public string DescribeNumbers(int[] numbers) => numbers switch
{
    [] => "Empty array",
    [1] => "Single item: 1",
    [1, 2] => "Exactly [1, 2]",
    [1, ..] => "Starts with 1",
    [_, _, 3] => "Ends with 3",
    [var first, var second, ..] => $"First two: {first}, {second}",
    _ => "Other array"
};

💡 Pattern Matching Tips

• Use switch expressions for concise logic
• Combine with property patterns
• Use when clauses for complex conditions
• Handle all cases in switch expressions
• Use patterns for validation