Develop Reference

Dictionary on multiple layers C#

everyone! Before i explain, i must say i tried to read some questions here similar to my case but couldn't get how to solve my problem, that's why i'm asking here.
Trying to put it simply, i'm working on a sort of database about Pokémon (so who knows Pokémon can understand what i'm doing) and i'm importing with json a txt file with the data i need. Until now i used a dual String dictionary structure (Dictionary String, String) to handle all data, like
"2"(this is a value used to handle the list of all Pokémon, in fact 2 is for ivysaur): {
"number": 2,
"national": "2",
"where_to_find": {
"red": "-",
"blue": "-",
"yellow": "-",
(and so on until shield, it's just a list of locations in every game where to find the pkmn)
}
and there is also more data structured like this, just as a single String key or Dictionary (dual String) like "where_to_find" as you can see above.
At the beginning of the code i created a class to handle the keys about every index in the list (every pkmn) and stated clearly
public Dictionary<String, String> where_to_find;
public String number;
public String national;
and all the rest. It works just fine. That's not the problem.
My problem is now i need to start handling the data in the txt file with a structure on multiple layers of String Keys. Since i never used such structure, i tried a simple stupid test and added in the txt file what follows (i added it at the first index, which would be Bulbasaur):
"hello": {
"hey": {
"hi": "greeting"
}
}
and above also stated that
public Dictionary<String, Dictionary<String, String>> hello;
As it recognised hello (when i write pokemon.hel, it suggests "hello" for auto-compile), but didn't recognise hey or hi, i also declared hey as a Dictionary String, String and hi as String.
BUT, this way it supposes it's pokemon.hey and pokemon.hi.
To be clear to you, think of this: suppose i want to bring up:
Messagebox.Show(pokemon.hello.hey.hi);
The messagebox in this case should write "greeting". What i can't get to do is this kind of formula, like pokemon.hello.hey.hi, or pokemon.hello["hey"["hi"]]. How can i do that? Thanks in advance for your suggestions and answers.

try hello["hey"]["hi"]
You are using the second index ([“hi”]) on the “hey” string, that expect an Int index, you should use it outside

Searching an array string with a binary search sub string

I have a file.txt containing about 200,000 records.
The format of each record is 123456-99-Text. The 123456 are unique account numbers, the 99 is a location code that I need (it changes from 01 to 99), and the text is irrelevant. These account numbers are sorted in order and with a line break in the file per ac(111111, 111112, 111113, etc).
I made a visual studio textbox and search button to have someone search for the account number. The account number is actually 11 digits long but only the first 6 matter. I wrote this as string actnum = textbox1.text.substring(0,6)
I wrote a foreach (string x in file.readline('file.txt')) with an if (x.contains(actnum)) then string code = x.substring(8,2)) statement.
The program works well, but because there are so many records if someone searches an account number that doesnt exist, or a number at the bottom of the list, the program locks up for a good 10 seconds before going to the "number not found" else statement, or taking forever to find that last record.
My Question:
Reading about binary searches I have attempted to try one without much success. I cannot seem to get the array or file to act like a legitimate binary search. Is there a way to take the 6 digit actnum from textbox1, compare it to an array substring of the 6 digit account number, then grab the substring 99 code from that specific line?
A binary search would help greatly! I could take 555-555 and compare it to the top or bottom half of the record file, then keep searching until i fine the line i need, grab the entire line, then substring the 99 out. The problem I have is I cant seem to get a proper integer conversion of the file because it contains both numbers AND text, and therefore I cant properly use <, >, = signs.
Any help on this would be greatly appreciated. The program I currently have actually works but is incredibly slow at times.

As one possible solution (not necessarily the best) you can add your record IDs to a Dictionary<string, int> (or even a Dictionary<long, int> if all record IDs are numeric) where each key is the ID of one line and each value is the line index. When you need to look up a particular record, just look in the dictionary (it'll do an efficient lookup for you) and gives you the line number. If the item is not there (non-existent ID), you won't find it in the dictionary.
At this point, if the record ID exists in the file, you have a line number - you can either load the entire file into memory (if it's not too big) or just seek to the right line and read in the line with the data.
For this to work, you have to go through the file at least once and collect all the record IDs from all lines and add them to the dictionary. You won't have to implement the binary search - the dictionary will internally perform the lookup for you.
Edit:
If you don't need all the data from a particular line, just one bit (like the location code you mentioned), you don't even need to store the line number (since you won't need to go back to the line in the file) - just store the location data as the value in the dictionary.
I personally would still store the line index because, in my experience, such projects start out small but end up collecting features and there'll be a point where you'll have to have everything from the file. If you expect this to be the case over time, just parse data from each line into a data structure and store that in the dictionary - it'll make your future life simpler. If you're very sure you'll never need more data than the one bit of information, you can just stash the data itself in the dictionary.
Here's a simple example (assuming that your record IDs can be parsed into a long):
public class LineData
{
public int LineIndex { get; set; }
public string LocationCode { get; set; }
// other data from the line that you need
}
// ...
// declare your map
private Dictionary<long, LineData> _dataMap = new Dictionary<long, LineData> ();
// ...
// Read file, parse lines into LineData objects and put them in dictionary
// ...
To see if a record ID exists, you just call TryGetValue():
LineData lineData;
if ( _dataMap.TryGetValue ( recordID, out lineData ) )
{
// record ID was found
}
This approach essentially keeps the entire file in memory but all data is parsed only once (at the beginning, during building the dictionary). If this approach uses too much memory, just store the line index in the dictionary and then go back to the file if you find a record and parse the line on the fly.

You cannot really do a binary search against file.ReadLine because you have to be able to access the lines in different order. Instead you should read the whole file into memory (file.ReadAllLines would be an option)
Assuming your file is sorted by the substring, you can create a new class that implements IComparer
public class SubstringComparer : IComparer<string>
{
public int Compare(string x, string y)
{
return x.Substring(0, 6).CompareTo(y.Substring(0, 6));
}
}
and then your binary search would look like:
int returnedValue = foundStrings.BinarySearch(searchValue, new SubstringComparer());

Assuming the file doesn't change often, then you can simply load the entire file into memory using a structure that handles the searching in faster time. If the file can change then you will need to decide on a mechanism for reloading the file, be it restarting the program or a more complex process.
It looks like you are looking for exact matches (searching for 123456 yields only one record which is labelled 123456). If that is the case then you can use a Dictionary. Note that to use a Dictionary you need to define key and value types. It looks like in your case they would both be string.

While I did not find a way to do a better type of search, I did manage to learn about embedded resources which considerably sped up the program. Scanning the entire file takes a fraction of a second now, instead of 5-10 seconds. Posting the following code:
string searchfor = textBox1.Text
Assembly assm = Assembly.GetExecutingAssembly();
using (Stream datastream = assm.GetManifestResourceStream("WindowsFormsApplication2.Resources.file1.txt"))
using (StreamReader reader = new StreamReader(datastream))
{
string lines;
while ((lines = reader.ReadLine()) != null)
{
if (lines.StartsWith(searchfor))
{
label1.Text = "Found";
break;
}
else
{
label1.Text = "Not found";
}
}
}

In C# can you split a string into variables?

I recently came across a php code where a CSV string was split into two variables:
list($this->field_one, $this->field_two) = explode(",", $fields);
I turned this into:
string[] tmp = s_fields.Split(',');
field_one = tmp[0];
field_two = tmp[1];
Is there a C# equivalent without creating a temporary array?

Jon Skeet said the right thing. GC will do the thing, don't you worry.
But if you like the syntax so much (which is pretty considerable), you can use this, I guess.
public static class MyPhpStyleExtension
{
public void SplitInTwo(this string str, char splitBy, out string first, out string second)
{
var tempArray = str.Split(splitBy);
if (tempArray.length != 2) {
throw new NotSoPhpResultAsIExpectedException(tempArray.length);
}
first = tempArray[0];
second = tempArray[1];
}
}
I almost feel guilty by writing this code. Hope this will do the thing.

The answer to your quite narrow question is no. C# does not provide a 'multi-assignment' capability, so you cannot extract an arbitrary set of values from anything (such as Split()) and break them out into individual named variables.
There is a workaround for a specific number of variables, by writing a parameter with out arguments. See #vlad for an answer based on that.
But why would you want to? C# provides an impressive range of features that will allow you to take apart strings and deal them with the parts in a such a wide range of different ways that the lack of 'multi-assignment' should barely be noticed.
Parsing strings usually involves other operations such as dealing with formatting errors, trimming white space, case folding. There could be less than 2 strings, or more. Requirements could change over time. When you are ready for a more capable string parser, C# will be waiting.

You may use the following approach:
-Create a class that inherits from dynamic object.
-Create a local dictionary that will store your variables values in the inherited class.
-Override the TryGetMember and TrySetMember functions to get and set values from and into the dictionary.
-Now, you can split your string and put it in the dictionary, then access your variable like:
dynamicObject.var1

Removing lines from a string + old entries from a Dictionary in C#

I have a Dictionary the first string, the key's, must never change.. it cant be deleted or anything.. but the value, i keep adding lines, and lines, and lines to the values.. i just create new lines with \r\n or \r .. and im just wondering what would be the easiest way to retain just the last 50 lines. and delete anything over the 50 lines.. im doing this because when i return it i have to put the values through a char array, and go through each letter, and this can be slow if there is too much data. any suggestions?

Guffa's general idea is right - your data structure should reflect what you actually want, which is a list of strings rather than a single string. The concept of "the last 50 lines" is pretty obviously to do with a collection rather than a single string, even if you've originally read it that way.
However, I'd suggest using a LinkedList<T> rather than a List<T>: every time you remove the first element of a List<T>, everything else has to shuffle up. List<T> is great for giving random access and not too bad at adding to the end, but sucks for removing from the start. LinkedList<T> is great at giving you iterator access, adding to / removing from the start, and adding to / removing from the end. It's a better fit. (If you really wanted to go to town you could even write your own fixed-size circular buffer type which encapsulated the logic for you; this would give the best of both worlds, in the situation where you don't want to be able to expand beyond a certain size.)
Regarding your comments to Guffa's answer: it's pretty common to convert input into a form which is more appropriate for processing, then convert it back to the original format for output. The reason why you do it is precisely the "more appropriate" bit. You don't want to have to parse the string for line breaks as part of the "updating the dictionary" action, IMO. In particular, it sounds like you're currently introducing the idea of "lines" where the original text is just being read in as strings. You're effectively creating your own "collection" class backed by a string, by delimiting strings with line breaks. That's inefficient, error-prone, and much harder to manage than using the built-in collections. It's easy to perform the conversion to a line-break-delimited string at the end if you want it, but it sounds like you're doing it way too early.

Instead of concatenating the lines, use a Dictionary<string, List<string>>. When you are about to add a string to the list you can check the count and remove the first string if the list already has 50 strings:
List<string> list;
if (!theDictionary.TryGetValue(key, out list)) {
theDictionary.Add(list = new List<string>());
}
if (list.Count == 50) {
list.RemoveAt(0);
}
list.Add(line);

Customizing Sort Order of C# Arrays

This has been bugging me for some time now. I've tried several approaches and none have worked properly.
I'm writing and IRC client and am trying to sort out the list of usernames (which needs to be sorted by a users' access level in the current channel).
This is easy enough. Trouble is, this list needs to added to whenever a user joins or leaves the channel so their username must be removed the list when the leave and re-added in the correct position when they rejoin.
Each users' access level is signified by a single character at the start of each username. These characters are reserved, so there's no potential problem of a name starting with one of the symbols. The symbols from highest to lowest (in the order I need to sort them) are:
~
&
#
%
+
Users without any sort of access have no symbol before their username. They should be at the bottom of the list.
For example: the unsorted array could contain the following:
~user1 ~user84 #user3 &user8 +user39 user002 user2838 %user29
And needs to be sorted so the elements are in the following order:
~user1 ~user84 &user8 #user3 %user29 +user39 user002 user2838
After users are sorted by access level, they also need to be sorted alphabetically.
Asking here is a last resort, if someone could help me out, I'd very much appreciate it.
Thankyou in advance.

As long as the array contains an object then implement IComparable on the object and then call Array.Sort().
Tho if the collection is changable I would recommend using a List<>.

You can use SortedList<K,V> with the K (key) implementing IComparable interface which then defines the criteria of your sort. The V can simply be null or the same K object.

You can give an IComparer<T> or a Comparison<T> to Array.Sort. Then you just need to implement the comparison yourself. If it's a relatively complex comparison (which it sounds like this is) I'd implement IComparer<T> in a separate class, which you can easily unit test. Then call:
Array.Sort(userNames, new UserNameComparer());
You might want to have a convenient instance defined, if UserNameComparer has no state:
Array.Sort(userNames, UserNameComparer.Instance);
List<T> has similar options for sorting - I'd personally use a list rather than an array, if you're going to be adding/removing items regularly.
In fact, it sounds like you don't often need to actually do a full sort. Removing a user doesn't change the sort order, and inserting only means inserting at the right point. In other words, you need:
Create list and sort it to start with
Removing a user is just a straightforward operation
Adding a user requires finding out where to insert them
You can do the last step using Array.BinarySearch or List.BinarySearch, which again allow you to specify a custom IComparer<T>. Once you know where to insert the user, you can do that relatively cheaply (compared with sorting the whole collection again).

You should take a look at the IComparer interface (or it's generic version). When implementing the CompareTo method, check whether either of the two usernames contains one of your reserved character. If neither has a special reserved character or both have the same character, call the String.CompareTo method, which will handle the alphabetical sorting. Otherwise use your custom sorting logic.

I gave the sorting a shot and came up with the following sorting approach:
List<char> levelChars = new List<char>();
levelChars.AddRange("+%#&~".ToCharArray());
List<string> names = new List<string>();
names.AddRange(new[]{"~user1", "~user84", "#user3", "&user8", "+user39", "user002", "user2838", "%user29"});
names.Sort((x,y) =>
{
int xLevel = levelChars.IndexOf(x[0]);
int yLevel = levelChars.IndexOf(y[0]);
if (xLevel != yLevel)
{
// if xLevel is higher; x should come before y
return xLevel > yLevel ? -1 : 1;
}
// x and y have the same level; regular string comparison
// will do the job
return x.CompareTo(y);
});
This comparison code can just as well live inside the Compare method of an IComparer<T> implementation.