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  • Java library for trees similar to JGraphT for graphs?

    - by lexicore
    I'm a big fan of JGraphT, a Java library for graphs. Could anyone recommend a similar Java library for trees? Preferrably FOSS. What I need is a good API, preferrably typesafe with generics which allows modelling different kinds of trees (with some user data attached to verticies/edges) and run different algorithms and operations on these trees. For instance, traverse or balance. At the moment I'm not interested in visualization of trees.

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  • Default values for Content Taxonomy fields in Drupal with Hierarchical Select widget

    - by lazysoundsystem
    I'm trying to set the default value for a Content Taxonomy field in a hook_form_alter, but can't pin down the necessary format. I've tried this and many variations: foreach (element_children($form) as $child) { // Set $default_value. if ($form[$child]['tids']) { // This, for Content Taxonomy fields, isn't working: $form[$child]['tids']['#default_value'] = array('value' => $default_value); dsm($form[$child]['tids']['#default_value']); } else { // This, for other fields, is working: $form[$child][0]['#default_value']['value'] = $default_value; } } Can anyone tell me what I'm missing? Edit: In response to Henrik Opel (thanks for getting involved), here is the print out of the relevant field of the form with my changes to the default fields commented out, showing the '#default_value' field I'm trying to influence. It also shows that the option widget I'm using is Hierarchical Select (could this be a factor?). In the dsm() in the code above, the changes to the default value are recognised, but they don't get processed later on. field_name_of_content_taxonomy_field (Array, 3 elements) #tree (Boolean) TRUE #weight (String, 1 characters ) 5 tids (Array, 7 elements) #title (String, 10 characters ) Vocabulary_name #type (String, 19 characters ) hierarchical_select #weight (String, 1 characters ) 5 #config (Array, 15 elements) // 15 elements here #required (String, 1 characters ) 0 #description (String, 0 characters ) #default_value (Array, 0 elements)

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  • Best method to search hierarchical data

    - by WDuffy
    I'm looking at building a facility which allows querying for data with hierarchical filtering. I have a few ideas how I'm going to go about it but was wondering if there are any recommendations or suggestions that might be more efficient. As an example imagine that a user is searching for a job. The job areas would be as follows. 1: Scotland 2: --- West Central 3: ------ Glasgow 4: ------ Etc 5: --- North East 6: ------ Ayrshire 7: ------ Etc A user can search specific (i.e. Glasgow) or in a larger area (i.e. Scotland). The two approaches I am considering are: keep a note of children in the database for each record (i.e. cat 1 would have 2, 3, 4 in its children field) and query against that record with a SELECT * FROM Jobs WHERE Category IN Areas.childrenField. Use a recursive function to find all results who have a relation to the selected area. The problems I see from both are: Holding this data in the db will mean having to keep track of all changes to structure. Recursion is slow and inefficent. Any ideas, suggestion or recommendations on the best approach? I'm using C# ASP.NET with MSSQL 2005 DB.

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  • Using custom DataContractResolver in WCF, to transport inheritance trees involving generics

    - by Benson
    I've got a WCF service, in which there are operations which accept a non-generic base class as parameter. [DataContract] class Foo { ... } This base class is in turn inherited, by such generics classes as [DataContract] class Bar : Foo { ... } To get this to work, I'd previously have to register KnownTypes for the Foo class, and have these include all possible variations of Bar (such as Bar, Bar and even Bar). With the DataContractResolver in .NET 4, however, I should be able to build a resolver which properly stores (and restores) the classes. My questions: Are DataContractResolvers typically only used on the service side, and not by the client? If so, how would that be useful in this scenario? Am I wrong to write a DataContractResolver which serializes the fully qualified type name of a generic type, such as Bar1[List1[string, mscorlib], mscorlib] ? Couldn't the same DataContractResolver on the client side restore these types?

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  • Dynamically loading sub-trees into YUI Treeview

    - by user319399
    When you create a YUI TreeView instance, you can pass in an object that represents an entire tree, and it will automatically build up the TextNodes for you. I'd like to send in a partial tree, such that the tree only goes, say, 2 levels deep, and anything deeper than that will invoke dynamic loading. I've got that much working. Now for the interesting part. In the dynamic loading callback I give to my tree instance, I want to again be able to just give YUI a big object representing more of the tree. I want to do something like this: // data is a array of objects organized into a tree, with some nodes requiring dynamic loading when they are navigated to tree = new YAHOO.widget.TreeView("treeDiv1", data); tree.setDynamicLoad(loadDataForNode); function loadDataForNode(node, onCompleteCallback) { if(node.children.length==0) { var subTree = { "label":"Cars", isLeaf:false, children:[ { "label":"Chevy", isLeaf:true }, { "label":"Ford", isLeaf:true }, ] }; // doesn't work, even though it has the required "label" field var tempNode = new YAHOO.widget.TextNode(subTree, node, true); } onCompleteCallback(); } Is this possible? Or do I have to iterate over all the nodes in my subtree and construct individual TextNodes for each one? Thanks much...

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  • Linux Kernel - Red/Black Trees

    - by CodeRanger
    I'm trying to implement a red/black tree in Linux per task_struct using code from linux/rbtree.h. I can get a red/black tree inserting properly in a standalone space in the kernel such as a module but when I try to get the same code to function with the rb_root declared in either task_struct or task_struct-files_struct, I get a SEGFAULT everytime I try an insert. Here's some code: In task_struct I create a rb_root struct for my tree (not a pointer). In init_task.h, macro INIT_TASK(tsk), I set this equal to RB_ROOT. To do an insert, I use this code: rb_insert(&(current-fd_tree), &rbnode); This is where the issue occurs. My insert command is the standard insert that is documented in all RBTree documentation for the kernel: int my_insert(struct rb_root *root, struct mytype *data) { struct rb_node **new = &(root->rb_node), *parent = NULL; /* Figure out where to put new node */ while (*new) { struct mytype *this = container_of(*new, struct mytype, node); int result = strcmp(data->keystring, this->keystring); parent = *new; if (result < 0) new = &((*new)->rb_left); else if (result > 0) new = &((*new)->rb_right); else return FALSE; } /* Add new node and rebalance tree. */ rb_link_node(&data->node, parent, new); rb_insert_color(&data->node, root); return TRUE; } Is there something I'm missing? Some reason this would work fine if I made a tree root outside of task_struct? If I make rb_root inside of a module this insert works fine. But once I put the actual tree root in the task_struct or even in the task_struct-files_struct, I get a SEGFAULT. Can a root node not be added in these structs? Any tips are greatly appreciated. I've tried nearly everything I can think of.

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  • Red-Black trees - Erasing a node with two non-leaf children

    - by SalamiArmi
    Hi all, I've been implementing my own version of a red-black tree, mostly basing my algorithms from Wikipedia (http://en.wikipedia.org/wiki/Red-black_tree). Its fairly concise for the most part, but there's one part that I would like clarification on. When erasing a node from the tree that has 2 non-leaf (non-NULL) children, it says to move either side's children into the deletable node, and remove that child. I'm a little confused as to which side to remove from, based on that. Do I pick the side randomly, do I alternate betweek sides, or do I stick to the same side for every future deletion?

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  • Repeated Scene Trees (Java3d / OpenGL)

    - by Jim
    Hello, I want to make a 3d scene that loops around on its self. That is to say, if you keep going in any direction, you will loop back to the other side. My current implementation is so bad, it's embarrassing to admit to it. I redraw the each change twenty-seven times, to make a 3x3x3 scene cube. When the user reaches the end of the middle cube, I jump them over to the other side. Maintaining consistency (let alone performance) is a nightmare. Total Disaster. This doesn't seem like it would be an unusual request, so I'm wondering if anyone knows of a more legit solution. Thanks!

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  • Insertions into Zipper trees on XML files in Clojure

    - by ivar
    I'm confused as how to idiomatically change a xml tree accessed through clojure.contrib's zip-filter.xml. Should be trying to do this at all, or is there a better way? Say that I have some dummy xml file "itemdb.xml" like this: <itemlist> <item id="1"> <name>John</name> <desc>Works near here.</desc> </item> <item id="2"> <name>Sally</name> <desc>Owner of pet store.</desc> </item> </itemlist> And I have some code: (require '[clojure.zip :as zip] '[clojure.contrib.duck-streams :as ds] '[clojure.contrib.lazy-xml :as lxml] '[clojure.contrib.zip-filter.xml :as zf]) (def db (ref (zip/xml-zip (lxml/parse-trim (java.io.File. "itemdb.xml"))))) ;; Test that we can traverse and parse. (doall (map #(print (format "%10s: %s\n" (apply str (zf/xml-> % :name zf/text)) (apply str (zf/xml-> % :desc zf/text)))) (zf/xml-> @db :item))) ;; I assume something like this is needed to make the xml tags (defn create-item [name desc] {:tag :item :attrs {:id "3"} :contents (list {:tag :name :attrs {} :contents (list name)} {:tag :desc :attrs {} :contents (list desc)})}) (def fred-item (create-item "Fred" "Green-haired astrophysicist.")) ;; This disturbs the structure somehow (defn append-item [xmldb item] (zip/insert-right (-> xmldb zip/down zip/rightmost) item)) ;; I want to do something more like this (defn append-item2 [xmldb item] (zip/insert-right (zip/rightmost (zf/xml-> xmldb :item)) item)) (dosync (alter db append-item2 fred-item)) ;; Save this simple xml file with some added stuff. (ds/spit "appended-itemdb.xml" (with-out-str (lxml/emit (zip/root @db) :pad true))) I am unclear about how to use the clojure.zip functions appropriately in this case, and how that interacts with zip-filter. If you spot anything particularly weird in this small example, please point it out.

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  • B-trees that use redistribution on insertion

    - by Phenom
    If I insert the following keys into a B-tree of order 4 (meaning 4 pointers and 3 elements in each node), I get the following B-tree. G / \ A IY Would it look any different if redistribution on insertion were used? How does redistribution on insertion work?

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  • Deeply nested subqueries for traversing trees in MySQL

    - by nickf
    I have a table in my database where I store a tree structure using the hybrid Nested Set (MPTT) model (the one which has lft and rght values) and the Adjacency List model (storing parent_id on each node). my_table (id, parent_id, lft, rght, alias) This question doesn't relate to any of the MPTT aspects of the tree but I thought I'd leave it in in case anyone had a good idea about how to leverage that. I want to convert a path of aliases to a specific node. For example: "users.admins.nickf" would find the node with alias "nickf" which is a child of one with alias "admins" which is a child of "users" which is at the root. There is a unique index on (parent_id, alias). I started out by writing the function so it would split the path to its parts, then query the database one by one: SELECT `id` FROM `my_table` WHERE `parent_id` IS NULL AND `alias` = 'users';-- 1 SELECT `id` FROM `my_table` WHERE `parent_id` = 1 AND `alias` = 'admins'; -- 8 SELECT `id` FROM `my_table` WHERE `parent_id` = 8 AND `alias` = 'nickf'; -- 37 But then I realised I could do it with a single query, using a variable amount of nesting: SELECT `id` FROM `my_table` WHERE `parent_id` = ( SELECT `id` FROM `my_table` WHERE `parent_id` = ( SELECT `id` FROM `my_table` WHERE `parent_id` IS NULL AND `alias` = 'users' ) AND `alias` = 'admins' ) AND `alias` = 'nickf'; Since the number of sub-queries is dependent on the number of steps in the path, am I going to run into issues with having too many subqueries? (If there even is such a thing) Are there any better/smarter ways to perform this query?

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  • Tortoise SVN diff two trees

    - by Midhat
    Hi Consider the following situation Code was added to the trunk at revision x A branch was created The modifications of rev x were removed from trunk in rev x+10 trunk and branch goes their own ways till rev x+100 Now we need to update the branch with changes form the trunk The problem with a simple "merge a range of revisions" is that due to step 3, the initial branch modifications are being removed. Is there any way to work around this without resorting to manual merge. Version Info: TortoiseSVN 1.6.7, Build 18415 - 32 Bit , 2010/01/22 17:55:06 Subversion 1.6.9,

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  • How to find longest common substring using trees?

    - by user384706
    The longest common substring problem according to wiki can be solved using a suffix tree. From wiki: The longest common substrings of a set of strings can be found by building a generalised suffix tree for the strings, and then finding the deepest internal nodes which have leaf nodes from all the strings in the subtree below it I don't get this. Example: if I have: ABCDE and XABCZ then the suffix tree is (some branches from XABCZ omitted due to space): The longest common substring is ABC but it is not I can not see how the description of wiki helps here. ABC is not the deepest internal nodes with leaf nodes. Any help to understand how this works?

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  • Data structure for unrooted trees

    - by Esmond
    I'm having problems figuring out how to build an unrooted tree with weighted edges and what data structure to store such a tree. An example of an unrooted tree would be like the one here: http://www.bio.davidson.edu/courses/GENOMICS/seq/unrooted.gif The problem i am having is the leaves would only have 1 link to the internal nodes and the internal nodes would have 3 links(the internal nodes would have 2 children and a link to another internal node). Do i have to distinguish between the 2 different kinds of nodes or can i have one class having the function of both types of nodes?

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  • merging 3 source versioned trees into 1

    - by user309779
    This is probably an easy question... I have 4 source versions of the same software in 4 different directories. I have just started using git for version control. To date, I have just been snapping a desperate copy rolling forward. I want to merge all versions (1.0.0.1, 1.0.0.2, 1.0.0.3, 1.0.1.0) together so that I will have a reference history. Opposed to just starting out with 1.0.1.0 as the initial version. I want to get this sort of thing right form the start. Can someone outline the basic steps to accomplish this? Thanks much, XO

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  • In B-trees which element gets promoted when the node splits

    - by Phenom
    Let's say there is a B-tree of order 8. This means it can have 8 pointers and 7 elements. Say the letters A through G are stored in this B-tree. So this B-tree is just a single node containing 7 elements. Then you try to insert J into the tree. There's no room, so you have to split the node and create a new root node. Which element gets promoted up into the root node?

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  • Can't use attached property on combobox inside hierarchical datatemplate WPF

    - by jesse_t_r
    I'm hoping to use an attached property to assign a command to the selection changed event of a combobox that is embedded inside a treeview. I'm attempting to set the attached property inside the hierchical data template for the tree but the command is not set and does not fire when the item in the combobox is changed. I've found that setting the attached property directly on a combobox outside of a datatemplate works fine; here is how I'm trying to set the property in the template: <HierarchicalDataTemplate x:Key="template1" ItemsSource="{Binding Path=ChildColumns}"> <Border Background="{StaticResource TreeItem_Background}" BorderBrush="Blue" BorderThickness="2" CornerRadius="5" Margin="2,5,5,2" HorizontalAlignment="Left" > <Grid> <Grid.ColumnDefinitions > <ColumnDefinition Width="Auto"/> <ColumnDefinition Width="*"/> <ColumnDefinition Width="*"/> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition /> <RowDefinition /> </Grid.RowDefinitions> <TextBlock MinWidth="80" HorizontalAlignment="Left" Grid.Column="0" Margin="5,2,2,2" Grid.Row ="0" Text="{Binding Path=ColName}"/> <ComboBox Name="cboColType" Grid.Column="1" HorizontalAlignment="Right" ItemsSource="{Binding Source={StaticResource dataFromEnum}}" SelectedItem="{Binding Path=ColumnType}" Margin="2,2,2,2" local:ItemSelectedBehavior.ItemSelected="{Binding Path=LoadConfigCommand}" /> </Grid> </Border> </HierarchicalDataTemplate> I also tried creating a style <Style x:Key="childItemStyle" TargetType="{x:Type FrameworkElement}"> <Setter Property="local:ItemSelectedBehavior.ItemSelected" Value="{Binding Path=LoadConfigCommand}" /> </Style> and setting the itemcontainerstyle to the style in the hierarchical datatemplate..still no luck .. <HierarchicalDataTemplate> ... <ComboBox Name="cboColType" Grid.Column="1" HorizontalAlignment="Right" ItemsSource="{Binding Source={StaticResource dataFromEnum}}" SelectedItem="{Binding Path=ColumnType}" Margin="2,2,2,2" ItemContainerStyle={StaticeResource childItemStyle}" /> ... </HierarchicalDataTemplate> I'm still learning a lot about WPF so I'm assuming there is something particular about the hierchical datatemplate that is not allowing the attache dproperty to be set..I have found similar posts in the forums and tried to implement their solutions as above, but after a day of searching and experimenting wiht no luck I'm hoping some one has an idea about this...

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  • How can I get objects and property values from expression trees?

    This is a follow-up to the Getting Information About Objects, Types, and Members with Expression Trees post, so I would recommend that you read that one first. Among other code examples in that blog post, I demonstrated how you can get a property name as a string by using expression trees. Here is the method. public static string GetName<T>(Expression<Func<T>> e) { var member = (MemberExpression)e.Body; return member.Member.Name; } And here is how you can use it. string...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • How can I get objects and property values from expression trees?

    This is a follow-up to the Getting Information About Objects, Types, and Members with Expression Trees post, so I would recommend that you read that one first. Among other code examples in that blog post, I demonstrated how you can get a property name as a string by using expression trees. Here is the method. public static string GetName<T>(Expression<Func<T>> e) { var member = (MemberExpression)e.Body; return member.Member.Name; } And here is how you can use it. string...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Is there a library that can decompile a method into an Expression tree, with support for CLR 4.0?

    - by Daniel Earwicker
    Previous questions have asked if it is possible to turn compiled delegates into expression trees, for example: http://stackoverflow.com/questions/767733/converting-a-net-funct-to-a-net-expressionfunct The sane answers at the time were: It's possible, but very hard and there's no standard library solution. Use Reflector! But fortunately there are some greatly-insane/insanely-great people out there who like reverse engineering things, and they make difficult things easy for the rest of us. Clearly it is possible to decompile IL to C#, as Reflector does it, and so you could in principle instead target CLR 4.0 expression trees with support for all statement types. This is interesting because it wouldn't matter if the compiler's built-in special support for Expression<> lambdas is never extended to support building statement expression trees in the compiler. A library solution could fill the gap. We would then have a high-level starting point for writing aspect-like manipulations of code without having to mess with raw IL. As noted in the answers to the above linked question, there are some promising signs but I haven't succeeded in finding if there's been much progress since by searching. So has anyone finished this job, or got very far with it? Note: CLR 4.0 is now released. Time for another look-see.

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  • hierachical query to return final row

    - by jeff
    I have a hierarchical query that doesn't return an expected row (employee badge = 444). TABLE: hr_data badge fname supervisor_badge 111 Jeff 222 222 Joe 333 333 John 444 444 Tom 444 SQL: SELECT CONNECT_BY_ISCYCLE As IC, badge, fname, supervisor_badge FROM hr_data START WITH badge = '111' CONNECT BY NOCYCLE badge = PRIOR supervisor_badge What is Returned: IC badge fname supervisor_badge 0 111 Jeff 222 0 222 Joe 333 1 333 John 444 What is Expected: IC badge fname supervisor_badge 0 111 Jeff 222 0 222 Joe 333 **0** 333 John 444 **1** 444 Tom 444 How can I get this query to return the employee Tom and then stop?

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  • Silverlight Tree View with Multiple Levels

    - by psheriff
    There are many examples of the Silverlight Tree View that you will find on the web, however, most of them only show you how to go to two levels. What if you have more than two levels? This is where understanding exactly how the Hierarchical Data Templates works is vital. In this blog post, I am going to break down how these templates work so you can really understand what is going on underneath the hood. To start, let’s look at the typical two-level Silverlight Tree View that has been hard coded with the values shown below: <sdk:TreeView>  <sdk:TreeViewItem Header="Managers">    <TextBlock Text="Michael" />    <TextBlock Text="Paul" />  </sdk:TreeViewItem>  <sdk:TreeViewItem Header="Supervisors">    <TextBlock Text="John" />    <TextBlock Text="Tim" />    <TextBlock Text="David" />  </sdk:TreeViewItem></sdk:TreeView> Figure 1 shows you how this tree view looks when you run the Silverlight application. Figure 1: A hard-coded, two level Tree View. Next, let’s create three classes to mimic the hard-coded Tree View shown above. First, you need an Employee class and an EmployeeType class. The Employee class simply has one property called Name. The constructor is created to accept a “name” argument that you can use to set the Name property when you create an Employee object. public class Employee{  public Employee(string name)  {    Name = name;  }   public string Name { get; set; }} Finally you create an EmployeeType class. This class has one property called EmpType and contains a generic List<> collection of Employee objects. The property that holds the collection is called Employees. public class EmployeeType{  public EmployeeType(string empType)  {    EmpType = empType;    Employees = new List<Employee>();  }   public string EmpType { get; set; }  public List<Employee> Employees { get; set; }} Finally we have a collection class called EmployeeTypes created using the generic List<> class. It is in the constructor for this class where you will build the collection of EmployeeTypes and fill it with Employee objects: public class EmployeeTypes : List<EmployeeType>{  public EmployeeTypes()  {    EmployeeType type;            type = new EmployeeType("Manager");    type.Employees.Add(new Employee("Michael"));    type.Employees.Add(new Employee("Paul"));    this.Add(type);     type = new EmployeeType("Project Managers");    type.Employees.Add(new Employee("Tim"));    type.Employees.Add(new Employee("John"));    type.Employees.Add(new Employee("David"));    this.Add(type);  }} You now have a data hierarchy in memory (Figure 2) which is what the Tree View control expects to receive as its data source. Figure 2: A hierachial data structure of Employee Types containing a collection of Employee objects. To connect up this hierarchy of data to your Tree View you create an instance of the EmployeeTypes class in XAML as shown in line 13 of Figure 3. The key assigned to this object is “empTypes”. This key is used as the source of data to the entire Tree View by setting the ItemsSource property as shown in Figure 3, Callout #1. Figure 3: You need to start from the bottom up when laying out your templates for a Tree View. The ItemsSource property of the Tree View control is used as the data source in the Hierarchical Data Template with the key of employeeTypeTemplate. In this case there is only one Hierarchical Data Template, so any data you wish to display within that template comes from the collection of Employee Types. The TextBlock control in line 20 uses the EmpType property of the EmployeeType class. You specify the name of the Hierarchical Data Template to use in the ItemTemplate property of the Tree View (Callout #2). For the second (and last) level of the Tree View control you use a normal <DataTemplate> with the name of employeeTemplate (line 14). The Hierarchical Data Template in lines 17-21 sets its ItemTemplate property to the key name of employeeTemplate (Line 19 connects to Line 14). The source of the data for the <DataTemplate> needs to be a property of the EmployeeTypes collection used in the Hierarchical Data Template. In this case that is the Employees property. In the Employees property there is a “Name” property of the Employee class that is used to display the employee name in the second level of the Tree View (Line 15). What is important here is that your lowest level in your Tree View is expressed in a <DataTemplate> and should be listed first in your Resources section. The next level up in your Tree View should be a <HierarchicalDataTemplate> which has its ItemTemplate property set to the key name of the <DataTemplate> and the ItemsSource property set to the data you wish to display in the <DataTemplate>. The Tree View control should have its ItemsSource property set to the data you wish to display in the <HierarchicalDataTemplate> and its ItemTemplate property set to the key name of the <HierarchicalDataTemplate> object. It is in this way that you get the Tree View to display all levels of your hierarchical data structure. Three Levels in a Tree View Now let’s expand upon this concept and use three levels in our Tree View (Figure 4). This Tree View shows that you now have EmployeeTypes at the top of the tree, followed by a small set of employees that themselves manage employees. This means that the EmployeeType class has a collection of Employee objects. Each Employee class has a collection of Employee objects as well. Figure 4: When using 3 levels in your TreeView you will have 2 Hierarchical Data Templates and 1 Data Template. The EmployeeType class has not changed at all from our previous example. However, the Employee class now has one additional property as shown below: public class Employee{  public Employee(string name)  {    Name = name;    ManagedEmployees = new List<Employee>();  }   public string Name { get; set; }  public List<Employee> ManagedEmployees { get; set; }} The next thing that changes in our code is the EmployeeTypes class. The constructor now needs additional code to create a list of managed employees. Below is the new code. public class EmployeeTypes : List<EmployeeType>{  public EmployeeTypes()  {    EmployeeType type;    Employee emp;    Employee managed;     type = new EmployeeType("Manager");    emp = new Employee("Michael");    managed = new Employee("John");    emp.ManagedEmployees.Add(managed);    managed = new Employee("Tim");    emp.ManagedEmployees.Add(managed);    type.Employees.Add(emp);     emp = new Employee("Paul");    managed = new Employee("Michael");    emp.ManagedEmployees.Add(managed);    managed = new Employee("Sara");    emp.ManagedEmployees.Add(managed);    type.Employees.Add(emp);    this.Add(type);     type = new EmployeeType("Project Managers");    type.Employees.Add(new Employee("Tim"));    type.Employees.Add(new Employee("John"));    type.Employees.Add(new Employee("David"));    this.Add(type);  }} Now that you have all of the data built in your classes, you are now ready to hook up this three-level structure to your Tree View. Figure 5 shows the complete XAML needed to hook up your three-level Tree View. You can see in the XAML that there are now two Hierarchical Data Templates and one Data Template. Again you list the Data Template first since that is the lowest level in your Tree View. The next Hierarchical Data Template listed is the next level up from the lowest level, and finally you have a Hierarchical Data Template for the first level in your tree. You need to work your way from the bottom up when creating your Tree View hierarchy. XAML is processed from the top down, so if you attempt to reference a XAML key name that is below where you are referencing it from, you will get a runtime error. Figure 5: For three levels in a Tree View you will need two Hierarchical Data Templates and one Data Template. Each Hierarchical Data Template uses the previous template as its ItemTemplate. The ItemsSource of each Hierarchical Data Template is used to feed the data to the previous template. This is probably the most confusing part about working with the Tree View control. You are expecting the content of the current Hierarchical Data Template to use the properties set in the ItemsSource property of that template. But you need to look to the template lower down in the XAML to see the source of the data as shown in Figure 6. Figure 6: The properties you use within the Content of a template come from the ItemsSource of the next template in the resources section. Summary Understanding how to put together your hierarchy in a Tree View is simple once you understand that you need to work from the bottom up. Start with the bottom node in your Tree View and determine what that will look like and where the data will come from. You then build the next Hierarchical Data Template to feed the data to the previous template you created. You keep doing this for each level in your Tree View until you get to the last level. The data for that last Hierarchical Data Template comes from the ItemsSource in the Tree View itself. NOTE: You can download the sample code for this article by visiting my website at http://www.pdsa.com/downloads. Select “Tips & Tricks”, then select “Silverlight TreeView with Multiple Levels” from the drop down list.

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  • How to set up Hierarchical Zend Rest Routes?

    - by Kenji Baheux
    With the Zend Framework, I am trying to build routes for a REST api on resources organized in the following pattern: http://example.org/users/ http://example.org/users/234 http://example.org/users/234/items http://example.org/users/234/items/34 How do I set up this with Zend_Rest_Route? Here is how I have setup the route for the users resource (users/:id) in my bootstrap.php file: $this->bootstrap('frontController'); $frontController = Zend_Controller_Front::getInstance(); $restRoute = new Zend_Rest_Route($frontController); $frontController->getRouter()->addRoute('default', $restRoute); [As far as I understand, this is a catch all route so users/324/items/34 would results in parameters set as id=324 and items=34 and everything would be mapped to the Users (front module) Model. From there I guess I could just test for the items parameter and retrieve the item #34 for user #324 on a get request.]<=== I just checked it and it doesn't seems to work like that: Acessing /users/234/items/43 and var_dump($this->_getAllParams()); in the get action of the rest controller results in the following output: array(4) { ["controller"]=> string(5) "users" ["action"]=> string(3) "get" [2]=> string(5) "items" ["module"]=> string(7) "default"] } Somehow both ids got lost... Anyone?

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