c# - Implementing custom IComparer (with example) -

c# - Implementing custom IComparer<> (with example) -

ive written next code, order strings native string.compare() allow collection of exceptions (in case custompriority) place priority on default string.compare() function.

it seems bit long winded, wondering if there built .net allow this?

var unorderered = new[] { "a", "b", "c", "x", "y", "z" }; var ordered = unorderered.orderby(a => a, new customstringcomparer()); //expected order y,x,a,b,c,z class customstringcomparer : icomparer<string> { int icomparer<string>.compare(string x, string y) { if (x == y) homecoming 0; else { //---------------------------- //beginning of custom ordering var custompriority = new[] { "y", "x" }; if (custompriority.any(a => == x) && custompriority.any(a => == y)) //both in custom ordered array { if (array.indexof(custompriority, x) < array.indexof(custompriority, y)) homecoming -1; homecoming 1; } else if (custompriority.any(a => == x)) //only 1 item in custom ordered array (and x) homecoming -1; else if (custompriority.any(a => == y)) //only 1 item in custom ordered array (and y) homecoming 1; //--------------------------- //degrade default ordering else homecoming string.compare(x, y); } } }

first, think it's useful restate problem: want sort by:

the index in given array; if item not in array, index infinity the string itself

that means can accomplish sort order using orderby() first status followed thenby() sec one:

private static uint negativetomaxvalue(int i) { if (i < 0) homecoming uint.maxvalue; homecoming (uint)i; } … var ordered = unorderered .orderby(a => negativetomaxvalue(array.indexof(new[] { "y", "x" }, a))) .thenby(a => a);

negativetomaxvalue() necessary, because items not in array should last, first normally, because index -1. (a hackish , unreadable way same straight cast result of indexof() uint.)

if wanted reuse sorting creating icomparer, believe there nil in .net help that. utilize comparerextensions instead:

icomparer<string> comparer = keycomparer<string> .orderby(a => negativetomaxvalue(array.indexof(new[] { "y", "x" }, a))) .thenby(a => a);

c# compare order icomparer