how to make a comparer function in c# code example

Example 1: c# string.compare

public static int Compare (string? strA, string? strB);
                                                                                 
//Less than zero strA precedes strB in the sort order
//zero strA occurs in the same position as strB in the sort order
//Greater than zero strA follows strB in the sort order

Example 2: c# comparer

public abstract class Comparer<T> : System.Collections.Generic.IComparer<T>, System.Collections.IComparer