c# - Sort and Group in LINQ -

-

i have list of string tuples, (p1,p2)

i'd know if there's linq statement group p1 (in ascending order), , have group contain p2 values group (in descending order).

for input: ("a","b"), ("a","c"), ("d","b") i'd 2 groups: "a" , "d" (in order, every time) group "a" contains "c" , "b" (in order, every time) , group "d" contains, well, "b".

is possible built-in linq classes or need iterate groups , sort them myself?

nope, it's not hard - need keep track of whether you're looking @ group or elements within group. here's sample query:

var query = tuple in tuples             orderby tuple.p1             group tuple.p2 tuple.p1 g             select new { group = g.key,                          elements = g.orderbydescending(p2 => p2) };

here's complete example (avoiding .net 4's tuple type simplicity if you're using .net 3.5):

using system; using system.collections.generic; using system.linq;  public class mytuple {     public string p1 { get; set; }     public string p2 { get; set; } }  class test {     static void main()     {         list<mytuple> tuples = new list<mytuple>         {             new mytuple { p1 = "a", p2 = "b" },             new mytuple { p1 = "a", p2 = "c" },             new mytuple { p1 = "d", p2 = "b" },         };          var query = tuple in tuples             orderby tuple.p1             group tuple.p2 tuple.p1 g             select new { group = g.key,                          elements = g.orderbydescending(p2 => p2) };          foreach (var group in query)         {             console.writeline("{0}:", group.group);             foreach (var value in group.elements)             {                 console.writeline("  {0}", value);             }         }     } }

note can simpler if you're happy ordering on "need know" basis:

var query = tuple in tuples     orderby tuple.p1     group tuple.p2 tuple.p1;  foreach (var group in query) {     console.writeline("{0}:", group.key);     foreach (var value in group.orderbydescending(x => x))     {         console.writeline("  {0}", value);     } }

Comments

Post a Comment

Popular posts from this blog

javascript - Enclosure Memory Copies -

-
function myclass() { //lots , lots of vars , code here. this.bar = function() { //do numerous enclosed myclass vars } this.foo = function() { alert('hello'); //don't enclosed variables. } } each instance of myclass gets own copy of bar , foo, why prototyped methods use less memory. however, know more memory use of inner methods. it seems obvious me (1) below must true. agree? not distinct myclass instances have own distinct copies of bar, must have own distinct copies of myclass enclosure. (or else how bar method keep myclass variables straight on per instance basis?) now (2) question i'm after. since inner foo method doesn't use in myclass enclosure natural qustion is: javascript smart enough not keep myclass enclosure in memory use of foo? this depend entirely on implementation not language. naive implementations keep far more around others. answer true e.g. v8 (chrome's js engine) may not true spider...
Read more

php - Replacing tags in braces, even nested tags, with regex -

-
example preg_replace('/\{[a-za-z.,\(\)0-9]+\}/', 'replaced', 'lorem ipsum dolor sit {tag1({tag2()})}, consectetur adipiscing elit.'); the result: lorem ipsum dolor sit {tag1(replaced)}, consectetur adipiscing elit. question as can see "tag2" has been replaced, want replace "tag1" know how can this? (in cases might this: {tag1({tag2({tag3()})})}) , on.) btw using preg_replace_callback, easier show preg_replace here site can test code: http://www.spaweditor.com/scripts/regex/index.php you need add curly braces character set. here's pattern used: /\{[a-za-z.,\(\)\{\}0-9]+\}/ and here result: "lorem ipsum dolor sit replaced, consectetur adipiscing elit."
Read more