c# - Get largest column name that come before a given column name in a list of Excel columns string -

please consider lists:

var list1 = {}; var list2 = {"a"}; var list3 = {"ae"}; var list4 = {"a", "b", "f", "h", "aa", "ac", "ae"}; 

this lists excel columns. want find column name come before given column name, example if want find column come before "n" want results lists:

null // list 1 "a"  // list 2 null // list 3 "h"  // list 4 

how can write linq query returns result me?

thanks

assuming list ordered, 1 possible way :

yourlist.takewhile(o => exceltonumber(o) < exceltonumber("n"))         .lastordefault(); 

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exceltonumber() method convert excel column name integer, mentioned in this post. included method definition below easy reference, credit 100% contributors of linked post :

int exceltonumber(string x) {     return x.aggregate(0, (s, c) => s * 26 + c - 'a' + 1); }