ComparerTDefault

ComparerTDefault refers to the default comparer instance supplied for a generic type parameter T, typically exposed in code as Comparer<T>.Default. It provides a standard mechanism for ordering values when no explicit comparer is supplied, and is commonly used by sorting and searching APIs.

How it works

The default comparer is designed to be versatile and lightweight. If T implements IComparable<T>, ComparerTDefault delegates comparison to that type-safe method. If not, but T implements IComparable, it uses that interface as a fallback. If neither interface is implemented, the default comparer cannot determine an ordering and will throw a runtime exception if asked to compare two elements. In many implementations, null values are treated as less than non-null values, and two nulls compare as equal.

Usage

ComparerTDefault is the underlying mechanism used by default sorting behavior. For example, in many environments, calling a sort method without providing a custom comparer will utilize ComparerTDefault to determine the order. It can also be retrieved explicitly via a static property like Comparer<T>.Default and passed to APIs that accept an IComparer<T>.

Design and characteristics

ComparerTDefault is typically implemented as a singleton per type T, constructed lazily and shared to avoid allocations. It is intended to be stateless and thread-safe. When possible, specialized paths are used to avoid boxing for value types that implement IComparable<T>, improving performance in generic code paths.

Limitations

For types that do not implement either IComparable<T> or IComparable, ComparerTDefault will not provide a meaningful ordering and will throw if used to compare instances. In such cases, a custom comparer should be supplied.

See also

IComparer<T>, IComparable<T>, Comparer<T>.Default.