I am joining a table to an in memory list and wanting to create an anonymous type from the results. I have joined the 2 data sources together ok, but I'm not sure of the syntax required to use a property from the in memory list in the anonymous type.
Here's my code
public DataKeys(IEnumerable<Element> elements)
{
var defsource = new DefinitionSource();
var items = from def in defsource.Definitions
where elements.Select(el=> el.Value).Contains(def.Name)
select new { def.Key };
...
}
(Obviously "elements" is an in-memory list of element and "DefinitionSource" is a wrapper around a table.) This works fine, but as you can see there is no property from the in-memory list of elements. I've tried this
var items = from def in defsource.Definitions
where elements.Select(el=> el.Value).Contains(def.Name)
from el in elements
where el.Value.Equals(def.Name)
select new { el.NodeType, def.Key };
but at run time it gens a "{"Local sequence cannot be used in LINQ to SQL implementations of query operators except the Contains operator."}"
So what is the syntax I need to do this?
Many thx IA
Simon
This might help:
var def=defsource.Definitions
.Where(a=>elements.Select(el=>el.Value).Contains(a.Name))
.ToList();
var items = from d in def
from el in elements
.Where(a=>a.Value==d.Name)
select new { el.NodeType, d.Key };
To query over two data sources both of them needs to be in memory are both of them should be in database. you can do the following to achieve the results you want
var query = (from def in defsource.Definitions
where elements.Select(el=> el.Value).Contains(def.Name)
).ToList();//bring filtered result in memory
var Items = from def in query //Definitions are already filtered no need to re-apply where
from el in elements.Where(a=>a.Value == def.Name)
select new {el.NodeType, def.Key};
Related
I'd like a user to be able to combine two items and if compatible will yield a new item. In this example, the item IDs will be saved as Strings.
I was wondering what the most efficient way to do this would be, while making sure that swapped order will always yield the same result, so the user could input the order:
item X + item Y = item Z
item Y + item X = item Z
I've tried using Dictionaries and Objects, but I just haven't been able to get anything to work. I've also tried some various libraries that include HashMap/HashSet but nothing is working. here's some pseduo-code:
itemRecipe1:HashSet = new HashSet();
itemRecipe1.add("2");//Add item with ID of 2
itemRecipe1.add("3");//Add item with ID of 3
inputRecipe:HashSet = new HashSet();
inputRecipe.add("3");//Add item with ID of 3 (swapped)
inputRecipe.add("2");//Add item with ID of 2 (swapped)
recipeList:HashMap = new HashMap();
receipeList.put(itemRecipe1, "11");//Recipe has been added, the result of the recipe should be item 11
//This should output as TRUE since the composition of itemRecipe1 and inputRecipe are the same, despite a different input order.
trace(receipeList.containsKey(inputRecipe));
If anyone has a solution for this issue, please elt me know as I am willing to implement any design I can get working. I just don't see how a Dictionary could work as the key order matters.
So you're trying to associate two or more objects with each other. The first thing you need is some primitive data you can use to represent each item uniquely, typically an ID. This should give you something like the following to begin with:
class Item {
public var _id:int;
public function Item(id:int) {
_id = id;
}
public function get id():int { return _id; }
}
Now you need some piece of data that establishes a relationship between multiple Items using this ID. That could be as simple as the following, with a little extra functionality thrown in to see if an input list of these IDs matches the relationship:
class ItemRelationship {
private var _items:Vector.<Item>;
public function ItemRelationship(items:Vector.<Item>) {
_items = items;
}
public function matches(ids:Vector.<int>):Boolean {
if (_items.length !== ids.length) {
return false;
}
for each (var item:Item in _items) {
var found:Boolean = false;
for each (var id:int in ids) {
if (item.id === id) {
found = true;
break;
}
}
if (!found) return false;
}
return true;
}
public function get items():Vector.<Item> { return _items; }
}
This lets us do something like this, assuming we have a bunch of items (item1, item2, ...) with IDs.
var rel:ItemRelationship = new ItemRelationship(new <Item>[item1, item2]);
And then:
trace(rel.matches(new <int>[1,2])); // true
trace(rel.matches(new <int>[2,1])); // true
trace(rel.matches(new <int>[3,4])); // false
Now all we need is something that stores all of these relationships and lets us fetch one based on a list of input IDs:
class RelationshipCollection {
private var _relationships:Vector.<ItemRelationship>;
public function RelationshipCollection(relationships:Vector.<ItemRelationship>) {
_relationships = relationships;
}
public function find(ids:Vector.<int>):ItemRelationship {
for each(var relationship:ItemRelationship in _relationships) {
if (relationship.matches(ids)) return relationship;
}
return null;
}
}
Put a load of relationships in there:
var collection:RelationshipCollection = new RelationshipCollection(new <ItemRelationship>[
new ItemRelationship(new <Item>[item1, item4]),
new ItemRelationship(new <Item>[item2, item3])
]);
And give it a whirl:
trace(collection.find(new <int>[1, 3])); // null (no match)
trace(collection.find(new <int>[1, 4])); // works
trace(collection.find(new <int>[3, 2])); // works
trace(collection.find(new <int>[2, 3])); // works
Of course for the sake of readability you can rename each class to something more appropriate for its application e.g. Item => Potion, ItemRelationship => Recipe, RelationshipCollection => RecipeBook.
so the user could input the order
The first step is to limit the possible input. If you allow any type of input, you have to parse that input and things get complicated very quickly.
Create an input method that only allows the user to put two items together, say for example via drag and drop of the items to only 2 slots.
I just don't see how a Dictionary could work as the key order matters.
The important part is to design the keys well.
As #George Profenza pointed out in the comments, you could change your IDs to a different format. Instead of having 1, 2, 3, ... n you could use 1, 2, 4, ... 2^n. The advantage is that you can combine any two IDs uniquely via bitwise or operator (|). In the following example, two such IDs are combined (binary notation):
00001
| 10000
--------
10001
As you can see, each ID occupies a separate position in binary: the 1st position and the 5th. Combining both via or operator means that now both 1st and 5th position are 1. The order doesn't matter. If you use such IDs in the form of powers of 2 you can combine them regardless of the order to form pairs, which can then be used as keys to a dictionary.
Another solution is to simply sort the pair of IDs.
The combination 3-2 becomes 2-3 and the combination 2-3 stays 2-3. Both 2-3 and 3-2 lead to the same result.
You can then build your data structure accordingly, that is: the outer data structure is for the lower ID number and the nested, inner one is for the bigger ID number. Here's some pseudo code with generic objects:
var map:Object = {};
map["2"] = {"3":"combination 2-3"};
To access that, you'd do something like:
trace(map[Math.min(ID1, ID2)][Math.max(ID1, ID2)])
There's also the brute force way of doing it by storing both possible combinations in the data structure. The code for that could roughly look like that:
var map:Object = {};
map["2"] = {"3":"combination 2-3"};
map["3"] = {"2":"combination 2-3"};
Now both
trace(map[ID1][ID2]);
and
trace(map[ID2][ID1]);
Should yield the same result.
I guess a step back is in order. My original question is at the bottom of this post for reference.
I am writing a word guessing game and wanted a way to:
1. Given a word length of 2 - 10 characters, randomly generate a valid english word to guess
2.given a 2 - 10 character guess, ensure that it is a valid english word.
I created a vector of 9 objects, one for each word length and dynamically created 172000
property/ value pairs using the words from a word list to name the properties and setting their value to true. The inner loop is:
for (i = 0; i < _WordCount[wordLength] - 2; i)
{
_WordsList[wordLength]["" + _WordsVector[wordLength][i++]] = true;
}
To validate a word , the following lookup returns true if valid:
function Validate(key:String):Boolean
{
return _WordsList[key.length - 2][key]
}
I transferred them from a vector to objects to take advantage of the hash take lookup of the properties. Haven't looked at how much memory this all takes but it's been a useful learning exercise.
I just wasn't sure how best to randomly choose a property from one of the objects. I was thinking of validating whatever method I chose by generating 1000 000 words and analyzing the statistics of the distribution.
So I suppose my question should really first be am I better off using some other approach such as keeping the lists in vectors and doing a search each time ?
Original question
Newbie first question:
I read a thread that said that traversal order in a for.. in is determined by a hash table and appears random.
I'm looking for a good way to randomly select a property in an object. Would the first element in a for .. in traversing the properties, or perhaps the random nth element in the iteration be truly random. I'd like to ensure that there is approximately an equal probability of accessing a given property. The Objects have between approximately 100 and 20000 properties. Other approaches ?
thanks.
Looking at the scenario you described in your edited question, I'd suggest using a Vector.<String> and your map object.
You can store all your keys in the vector and map them in the object, then you can select a random numeric key in the vector and use the result as a key in the map object.
To make it clear, take a look at this simple example:
var keys:Vector.<String> = new Vector.<String>();
var map:Object = { };
function add(key:String, value:*):void
{
keys.push(key);
map[key] = value;
}
function getRandom():*
{
var randomKey = keys[int(Math.random() * keys.length)];
return map[randomKey];
}
And you can use it like this:
add("a", "x");
add("b", "y");
add("c", "z");
var radomValue:* = getRandom();
Using Object instead of String
Instead of storing the strings you can store objects that have the string inside of them,
something like:
public class Word
{
public var value:String;
public var length:int;
public function Word(value:String)
{
this.value = value;
this.length = value.length;
}
}
Use this object as value instead of the string, but you need to change your map object to be a Dictionary:
var map:Dictionary = new Dictionary();
function add(key:Word, value:*):void
{
keys.push(key);
map[key] = value;
}
This way you won't duplicate every word (but will have a little class overhead).
I'm preparing data for a datatable in Linq2Sql
This code highlights as a 'Possible multiple enumeration of IEnumerable' (in Resharper)
// filtered is an IEnumerable or an IQueryable
var total = filtered.Count();
var displayed = filtered
.Skip(param.iDisplayStart)
.Take(param.iDisplayLength).ToList();
And I am 100% sure Resharper is right.
How do I rewrite this to avoid the warning
To clarify, I get that I can put a ToList on the end of filtered to only do one query to the Database eg.
var filteredAndRun = filtered.ToList();
var total = filteredAndRun.Count();
var displayed = filteredAndRun
.Skip(param.iDisplayStart)
.Take(param.iDisplayLength).ToList();
but this brings back a ton more data than I want to transport over the network.
I'm expecting that I can't have my cake and eat it too. :(
It sounds like you're more concerned with multiple enumeration of IQueryable<T> rather than IEnumerable<T>.
However, in your case, it doesn't matter.
The Count call should translate to a simple and very fast SQL count query. It's only the second query that actually brings back any records.
If it is an IEnumerable<T> then the data is in memory and it'll be super fast in any case.
I'd keep your code exactly the same as it is and only worry about performance tuning when you discover you have a significant performance issue. :-)
You could also do something like
count = 0;
displayed = new List();
iDisplayStop = param.iDisplayStart + param.iDisplayLength;
foreach (element in filteredAndRun) {
++count;
if ((count < param.iDisplayStart) || (count > iDisplayStop))
continue;
displayed.Add(element);
}
That's pseudocode, obviously, and I might be off-by-one in the edge conditions, but that algorithm gets you the count with only a single iteration and you have the list of displayed items only at the end.
Introduction:
I have an AdvancedDataGrid displaying hierarchical data illustrated by the image below:
The branch nodes "Prosjekt" and "Tiltak" display the sum of the leaf nodes below.
Problem: I want the root node "Tavle" to display the total sum of the branch nodes below. When i attempted to do this by adding the same SummaryRow the sum of the root node was not calculcated correctly(Every node's sum was calculated twice).
dg_Teknikktavles = new AutoSizingAdvancedDataGrid();
dg_Teknikktavles.sortExpertMode="true";
dg_Teknikktavles.headerHeight = 50;
dg_Teknikktavles.variableRowHeight = true;
dg_Teknikktavles.addEventListener(ListEvent.ITEM_CLICK,dg_TeknikktavlesItemClicked);
dg_Teknikktavles.editable="false";
dg_Teknikktavles.percentWidth=100;
dg_Teknikktavles.minColumnWidth =0.8;
dg_Teknikktavles.height = 1000;
var sumFieldArray:Array = new Array(context.brukerList.length);
for(var i:int = 0; i < context.brukerList.length; i++)
{
var sumField:SummaryField2 = new SummaryField2();
sumField.dataField = Ressurstavle.ressursKey + i;
sumField.summaryOperation = "SUM";
sumFieldArray[i] = sumField;
}
var summaryRow:SummaryRow = new SummaryRow();
summaryRow.summaryPlacement = "group";
summaryRow.fields = sumFieldArray;
var summaryRow2:SummaryRow = new SummaryRow();
summaryRow2.summaryPlacement = "group";
summaryRow2.fields = sumFieldArray;
var groupField1:GroupingField = new GroupingField();
groupField1.name = "tavle";
//groupField1.summaries = [summaryRow2];
var groupField2:GroupingField = new GroupingField();
groupField2.name = "kategori";
groupField2.summaries = [summaryRow];
var group:Grouping = new Grouping();
group.fields = [groupField1, groupField2];
var groupCol:GroupingCollection2 = new GroupingCollection2();
groupCol.source = ressursTavle;
groupCol.grouping = group;
groupCol.refresh();
Main Question: How do i get my AdvancedDataGrid's (dg_Teknikktavles) root node "Tavle" to correctly display the sum of the two branch nodes below?
Side Question: How do i add a red color to the numbers of the root node's summary row that exceed 5? E.g the column displaying 8 will exceed 5 in the root node's summary row, and should therefore be marked red
Thanks in advance!
This is a general answer, without code examples, but I had to do the same just couple of days ago, so my memory is still fresh :) Here's what I did:
Created a class A to represent an item renderer data, extended it from Proxy (I had field names defined at run time), and let it contain a collection of values as it's data member. Once accessed through flash_proxy::getPropery(fieldName) it would find a corresponding value in the data member containing the values and return it. Special note: implement IUID, just do it, it'll save you couple of days of frustration.
Extended A in B, added a children property containing ArrayCollection of A (don't try to experiment with other collection types, unless you want to find yourself examining tons of framework code, trust me, it's ugly and is impossible to identify as interesting). Let B override flash_proxy::getPropery - depending of your compiler this may, or may not be possible, if not possible - call some function from A.flash_proxy::getPropery() that you can override in B. Let this function query every instance of A, which is a child of B, asking the same thing, as DataGrid itself would, when building item renderers - this way you would get the total.
When creating a data provider. Create an ArrayCollection of B (again, don't try to experiment with other collections--unless you are ready for lots of frustration). Create Hierarchical data that uses this array collection as a source.
Colors - that's what you use item renderers for, just look up any tutorial on using item renderers, that must be pretty basic.
In case someone else has the same problem:
The initial problem that everything was summed twice, was the result of using the same Array of SummaryField2 (sumFieldArray in the code) for both grouping fields(GropingField2 tavle and kategori)
The Solution to the main question: was to create a new array of summaryfields for the root node(in my intial for loop):
//Summary fields for root node
var sumFieldRoot:SummaryField2 = new SummaryField2();
sumFieldRoot.dataField = Ressurstavle.ressursKey + i;
sumFieldRoot.summaryOperation = "SUM";
sumFieldArrayRoot[i] = sumFieldRoot;
Answer to the side question:
This was pretty much as easy as pointed out by wvxyw. Code for this solution below:
private function summary_styleFunction(data:Object, col:AdvancedDataGridColumn):Object
{
var output:Object;
var field:String = col.dataField;
if ( data.children != null )
{
if(data[field] >5){
output = {color:0xFF0000, fontWeight:"bold"}
}
else {
output = {color:0x006633, fontWeight:"bold"}
}
//output = {color:0x081EA6, fontWeight:"bold", fontSize:14}
}
return output;
}
My appologies upfront for the lengthy question. I made quite an effort to make my question as clear as possible in one go. Please bear with me. ;o) any help will be greatly appreciated!
I have the classes Branch and Text:
class Branch
int ID
Text WebDescription
and a bunch of other properties
class Text
int ID
string UK
string NL
string FR
string IT
and a bunch of other properties as well
I want to only display the ID of the branch and its description in the appropriate language. I want only one query (no extra round trips) which retrieves only two fields (not the whole object).
I found three solutions
Via the object model in the query
// good: no round trips
// good: clean sql
// bad: impossible to use the currentUserLanguage parameter
var lang = "NL";
var dbProject = new ProjectDataContext();
var query = from b in dbProject.GetTable<Branch>()
select new
{
b.ID,
WebDescription = b.WebDescriptionObject.NL // <-- problem
};
var text = query.First().WebDescription;
Via the object model after the query
// good: no round trips (eager loading of text object)
// good: possible to use the currentUserLanguage parameter
// bad: loads the *whole* branch and text object, not just two fields
var lang= "NL";
var dbProject = new ProjectDataContext();
var query = from b in dbProject.GetTable<Branch>()
select new
{
b.ID,
WebDescription = b.GetWebDescriptionAsString(lang)
};
var text = query.First().WebDescription;
Using an expression
// good: I have the feeling I am on the right track
// bad: This doesn't work :o( throws an exception
var lang= "NL";
var dbProject = new ProjectDataContext();
var query = from b in dbProject.GetTable<Branch>()
select new
{
b.ID,
WebDescription = b.GetWebDescriptionAsExpression(lang)
};
var text = query.First().WebDescription;
Here is code for the two methods GetWebDescriptionAsString and GetWebDescriptionAsExpression.
public string GetWebDescriptionAsString(string lang)
{
if (lang== "NL") return WebDescriptionObject.NL;
if (lang== "FR") return WebDescriptionObject.FR;
if (lang== "IT") return WebDescriptionObject.IT;
return WebDescriptionObject.UK;
}
public Expression<Func<Branch, string>> GetWebDescriptionAsExpression(string lang)
{
if (lang== "NL") return b => b.WebDescriptionObject.NL;
if (lang== "FR") return b => b.WebDescriptionObject.FR;
if (lang== "IT") return b => b.WebDescriptionObject.IT;
return b => b.WebDescriptionObject.UK;
}
Without really answering the question, the cleanest approach would be to change the Text structure into a more normalized form like:
Text
ID
TextTranslation
ID
TextID
Lang
TextValue
where each text has a number of translations, one for each language.
The query would become something like:
var q =
from branch in dbProject.Branches
join text in dbProject.Texts on branch.TextID = text.ID
join translation in dbProject.TextTranslations on text.ID = translation.TextID
where translation.Lang == lang
select new
{
branch.ID,
WebDescription = translation.TextValue
};
This approach has other advantages as well, for example adding a new language will not change the model structure.
This would be very easy to do if you used a stored procedure. Are you opposed to using SP's as a solution?
If a stored procedure works, then I am happy to use it.
Thank you for you prompt reply.
I made a quick attempt. The UDF was already there, I just didn't know how to use it. The performance dropped significantly. The first solution is 3 times faster. In my understanding, this approach would require extra round trips to the database. Is that correct?
var query = from b in dbProject.GetTable<Branch>()
select new
{
b.ID,
WebDescription = db.fGetText(b.WebDescriptionID, (currentUserLanguage))
};
Without understanding your whole problem
create a stored procedure like this:
CREATE PROCEDURE spGetTheTextINeed #Language char(2), #BranchID int
AS
/* I don't know how your database is structured so you need to write this */
SELECT MyText from MyTable WHERE Language=#Language and Branch=#BranchID
Then you need to add the sp to your DBML and then you can just call the sp you need with the appropriate parameters:
var query = myDataContext.spGetTheTextINeed("NL",[your branch number])
Dim str As String
str = query.MyText
The code above is not to be exact - I don't understand your full requirements but this should get you started.