Arrays of elements that belong to a custom type cannot be sorted, unless the type implements the IComparableinterface.
To make elements of a custom type sortable, you need to implement IComparable in your type. IComparableconsists of the single method CompareTo, which compares two objects.
Here’s an example of a Person class implementing CompareTo to sort people in LastName/FirstName order:
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| public int CompareTo(object obj){ Person other = obj as Person; if (other == null) throw new ArgumentException("Object is not a Person"); else { // Sort by LastName, then by FirstName (ignore case) int compare = this.LastName.ToLower().CompareTo(other.LastName.ToLower()); if (compare == 0) compare = this.FirstName.ToLower().CompareTo(other.FirstName.ToLower()); return compare; } |
Here’s an example of sorting an array of Person objects:
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| Person[] folks = new Person[4];folks[0] = new Person("Bronte", "Emily");folks[1] = new Person("Bronte", "Charlotte");folks[2] = new Person("Tennyson", "Alfred");folks[3] = new Person("Mailer", "Norman");Array.Sort(folks); // C. Bronte, E. Bronte, Mailer, Tennyson |