C# 2D array with string keys and int values -

i'm trying create data structure looks following:

             xls | doc | ppt | pdf            |--------------------- app/xls    |  1  |  0  |  0  |  0   app/msword |  1  |  1  |  0  |  0 app/ppt    |  0  |  0  |  1  |  0 app/pdf    |  0  |  0  |  0  |  1 

basically have list of lists in have information like:

[ext, xls], [mime, app/xls] [ext, ppt], [mime, app/ppt] [ext, doc], [mime, app/msword] [ext, xls], [mime, app/msword] 

note extension doesn't match appropriate mime value. reason wanting output table able see graphically distribution of extensions not mapped correct mime.

so can loop through list of lists , access each document both ext , mime, can't head around how extract/store hence output information in tabular form. have dictionary of correct ext-mime, important ensuring diagonal line top-left of table bottom-right, place should have non-zero values if data correct (because order of column-row matters in case).

so go here?!

if understand question, looping through bunch of data , populating numbers (0's , 1's, 2's.. n++) in above structure.

without getting fancy, i'd use

d = new dictionary<string, dictionary<string, int>>();    

if wanted fancy, i'd create class had following:

• a list of horizontal keys seen far
• a list of vertical keys seen far
• a dictionary of "key1#key2" value of 0|1|2...
• a "setter" of (key1,key2) => add horizontal keys and/or vertical keys if doesn't exist
• a "getter" of (key1,key2) => retrieves value out of dictionary

this allow pull out in nice pretty grid minimal effort, while maintaining decent write speed. let sort rows / columns in whichever way want. if added "optimalmapping" let know mimetype maps extension, can add check see if optimal or not.