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  • What You Need to Know About SEO

    Search Engine Optimization is commonly the technique utilized where websites prepare themselves for a higher ranking within the major online search engines. Various methods are applies as well as the careful selection of keywords. Don't forget the navigation of hierarchy and back links.

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  • How to Choose an SEO Company

    Having a website or blog that appears in the first page of the search engine results is necessary if you want people to find your website when searching the internet for information. It's also the hardest part of any web-based project! Many people and small companies looking to increase their online visibility will look to professional search engine optimization (SEO) companies to help optimize their websites and increase site visitors.

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  • SEO Mistakes to Be Avoided!

    As a beginner in search engine optimization, it is easy to make some of the most common mistakes people make. In short, search engines are designed to respond only to the websites and its pages, not to your lack of experience in creating them. This often leads to individuals who have the willingness to do really well and have all the right intentions but seem to be lacking in the actual ability to put together an effective website.

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  • Why SEO is Important

    Websites are only as good as those customers and clients who find them (and order your products and services). However, search engines need to find your websites as well and that's when search engine optimization - also known as SEO - comes into play.

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  • What Affects Your PageRank and How Can You Increase It?

    Your PageRank determines how likely it is that viewers will see your SEO website in the search results. The higher your rank, the more visitors will come to your website looking for information on what they put in the search box. This is a very simple way to put it, but it all boils down to the closer to number one you are, the more money you will make.

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  • A Guide to Google PageRank

    Getting to the top of Google for search terms related to your industry is one of the main goals of many modern businesses. There are many crucial factors which can determine how high you appear in SERP (Search Engine Results Page), one of which is Google PageRank.

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  • Importance of Content Part 2

    It is a simple fact that the more effort you put in your internal working, the better fruits you get from the external world. So if you want your business to give you the rewards that you desire, you will have to do a search engine optimization or a little search engine marketing for yourself.

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  • Is SEO a Four-Letter Word? It Doesn't Have to Be!

    Small business website owners have heard that they have to optimize their websites for the search engines otherwise they will languish on page 50 of Google for ever! Well, as with everything there is some truth to the need to make sure the search engines find your website.

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  • Basics of SEO

    SEO stands for "search engine optimization." It is the process of promoting a website to such an extent that it starts appearing on the search engine results page (SERPS).

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  • What Affects Your PageRank and How Can You Increase It?

    Your PageRank determines how likely it is that viewers will see your SEO website in the search results. The higher your rank, the more visitors will come to your website looking for information on what they put in the search box. This is a very simple way to put it, but it all boils down to the closer to number one you are, the more money you will make.

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  • 5 Don'ts of SEO Copywriting

    Do not include as many keywords as you can in the content. Yes, Google and other search engines should be able to follow what the page is about and yes, they look to match the search query with the content on the web page.

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  • Struts 1 ActionForm - retrieving a collection from pure HTML

    - by Yaneeve
    Hi all I have (just like the rest) inherited some struts 1 code. I have had need to add a few more pages to this project. What I cannot figure out is how to map several distinct but similarly natured input elements to the my ActionForm. Let me elaborate. I create a new <Input> element dynamically as the user inputs more and more items (I use the YUI autocomplete form element and for each entered input I add it as an input element to my form and draw a new YUI autocomplete - complex sounding, I know) So... My form looks a bit like (... after some prettifying and some such...): <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <meta http-equiv="content-type" content="text/html; charset=utf-8"> <title>My Cool App - Test Case Builder</title> <link rel="stylesheet" type="text/css" href="../script/yui/fonts/fonts-min.css" /> <link rel="stylesheet" type="text/css" href="../skins/myCoolApp/button/button.css" /> <link rel="stylesheet" type="text/css" href="../script/yui/autocomplete/assets/skins/sam/autocomplete.css" /> <link rel="stylesheet" type="text/css" media="screen" href="../skins/myCoolApp/testcase.css" /> <!-- YUI JAVA SCRIPTS --> <script type="text/javascript" src="../script/yui/yahoo-dom-event/yahoo-dom-event.js"></script> <script type="text/javascript" src="../script/yui/element/element-min.js"></script> <script type="text/javascript" src="../script/yui/button/button-min.js"></script> <script type="text/javascript" src="../script/yui/datasource/datasource-min.js"></script> <script type="text/javascript" src="../script/yui/autocomplete/autocomplete-min.js"></script> <!-- APP JAVA SCRIPTS --> <script type="text/javascript" src="../script/myCoolApp/myCoolApp.js" ></script> <script type="text/javascript" src="../script/myCoolApp/stack.js" ></script> <script type="text/javascript" src="../script/myCoolApp/testcase/testcase.js"></script> <script type="text/javascript" src="../script/myCoolApp/testcase/default-data.js" ></script> <script type="text/javascript" src="../script/myCoolApp/testcase/data-structs.js" ></script> <script type="text/javascript" src="../script/myCoolApp/testcase/ui-elements.js" ></script> </head> <body class="cf010"> <div id="wrap"> <div id="header"> <div id="main-header"> COOL APP </div> </div> <div id="main-body"> <div id="content"> <div class="col main"> <div id="main"> <form method="post" id="testcaseForm" class="typea" action=""> <fieldset> <legend>Test Case Builder</legend> <div id="tk1" class="tabcontrol"> <ul class="tabs"> <li class="first active"> <a href="#"> <span>General</span> </a> </li> <li class="last"> <a href="#"> <span>Parameters</span> </a> </li> </ul> <div id="tab0" class="tc-panel"> <dl class="cls9"> <dt> <label for="scenario">Choose Scenario:</label> </dt> <dd> <input type="text" id="scenario" name="scenario" class="text" /> <span id="scenarioToggle"></span> <div class="auto-complete" id="scenarioContainer"></div> </dd> <dt> <label for="ruleID">Choose Rule ID:</label> </dt> <dd> <input type="text" id="ruleID" name="ruleID" class="text" /> <span id="ruleIDToggle"></span> <div class="auto-complete" id="ruleIDContainer"></div> </dd> <dt> <label for="Test Case Name" accesskey="t"><span class="accesskey">T</span>est Case Name:</label> </dt> <dd> <input type="text" id="testCaseName" name="testCaseName" class="text" /> </dd> </dl> </div> <div id="tab1" class="tc-panel hidden"> <div class="toolbar" id="action-bar"> <ul> <li class="first"> <a title="select all" href="#" id="btmSelectAll" class="button"> <span>select all</span> </a> </li> <li> <a title="remove row" href="#" id="btmRemove" class="button"> <span>remove row</span> </a> </li> <li> <a title="undo last" href="#" id="btmRollBack" class="button disabled"> <span>undo last</span> </a> </li> <li class="last"> <a title="accept row" href="#" id="btmAccept" class="button disabled"> <span>accept row</span> </a> </li> </ul> </div> <div id="param.list" class="gridclip"> <table id='param.list.tbl' class='grid modela' > <caption>Test Case Summary</caption> <col/><col/><col/> <thead> <tr> <th class='hl center first'> <input class='grid-select-all' type='checkbox' /> <th> <th scope='col'>Row</th> <th scope='col'>Parameter</th> <th scope='col' class='last'>Value</th> </tr> </thead> <tfoot> <tr> <th scope='row'>Total</th> <td colspan='3'>2 parameters as Test Case input</td> </tr> </tfoot> <tbody id='param.list.tbl.body'> <tr class='odd'> <td class='rowcheck center first'> <input value='param1###value1' id='cb1' name='SelectedRows' class='grid-select-row' type='checkbox'/> </td> <td class='id'>1</td> <td>param1</td> <td class='last'>value1</td> </tr> <tr class='even'> <td class='rowcheck center first'> <input value='param2###value2' id='cb1' name='SelectedRows' class='grid-select-row' type='checkbox'/> </td> <td class='id'>2</td> <td>param2</td> <td class='last'>value2</td> </tr> <tr class='odd'> <td class='rowcheck center first' /> <td class='id'><em>new</em></td> <td> <dl class='clsTable'> <dt> <input type='text' id='param' name='param' class='text paramInput' /> </dt> <dd> <span id='paramToggle' /> </dd> <div class='auto-complete' id='paramContainer' /> </dl> </td> <td class='last'> <dl class='clsTable'> <dt> <input type='text' id='value' name='value' class='text valueInput' /> </dt> </dl> </td> </tr> </tbody> </table> </div> </div> </div> <!-- tabcontrol --> </fieldset> <div class="submit-box"> <input type="submit" name="formRun" id="formRun" class="form-save" value="Execute" accesskey="x" title="Run: Press Alt + [Shift] + x" /> <input type="submit" name="formSave" id="formSave" value="Save" accesskey="s" title="Save: Press Alt + [Shift] + s" /> <input type="submit" name="formLoad" id="formLoad" value="Load" accesskey="l" title="Load: Press Alt + [Shift] + l" /> <input type="submit" name="formCancel" id="formCancel" class="form-cancel" value="Cancel" accesskey="c" title="Cancel: Press Alt + [Shift] + c" /> </div> </form> </div> </div> </div> </div> </div> </body> </html> As you can see the following is pretty much a duplicate: <tr class='odd'> <td class='rowcheck center first'> <input value='param1###value1' id='cb1' name='SelectedRows' class='grid-select-row' type='checkbox'/> </td> <td class='id'>1</td> <td>param1</td> <td class='last'>value1</td> </tr> <tr class='even'> <td class='rowcheck center first'> <input value='param2###value2' id='cb1' name='SelectedRows' class='grid-select-row' type='checkbox'/> </td> <td class='id'>2</td> <td>param2</td> <td class='last'>value2</td> </tr> The relevant part of my stuts-config.xml file is: <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE struts-config PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 1.2//EN" "http://struts.apache.org/dtds/struts-config_1_2.dtd"> <struts-config> <data-sources /> <form-beans> <form-bean name="TestCaseForm" type="com.blahblah.mycoolapp.forms.TestCaseForm" /> </form-beans> <action-mappings> <action path="/pages/SaveTestCase" name="TestCaseForm" type="org.springframework.web.struts.DelegatingActionProxy" scope="request"> </action> </action-mappings> <message-resources parameter="MessageResources" /> </struts-config> I also use spring 2.56 (The relevant part being): <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"> <bean name="/pages/SaveTestCase" class="com.blahblah.mycoolapp.actions.TestCaseBuilderSaveAction" /> </beans> My Java ActionForm class (from what I had learned off the net) is: package com.blahblah.mycoolapp.forms; import java.util.ArrayList; import java.util.List; import org.apache.struts.action.ActionForm; public class TestCaseForm extends ActionForm { private static final long serialVersionUID = 2352146257739099766L; private String scenario; private String ruleID; private String testCaseName; private List<String> SelectedRows = new ArrayList<String>() ; public String getScenario() { return scenario; } public void setScenario(String scenario) { this.scenario = scenario; } public String getRuleID() { return ruleID; } public void setRuleID(String ruleID) { this.ruleID = ruleID; } public String getTestCaseName() { return testCaseName; } public void setTestCaseName(String testCaseName) { this.testCaseName = testCaseName; } public List<String> getSelectedRows() { return SelectedRows; } public void setSelectedRows(int index, String value) { this.SelectedRows.add(value); } } The question is why do I get an empty SelectedRows in my TestCaseBuilderSave Action? Thanks all who have the patience to read such a long question... and (hopefully) thanks to all you potential saviors :)

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  • How to compile a C++ source code written for Linux/Unix on Windows Vista (code given)

    - by HTMZ
    I have a c++ source code that was written in linux/unix environment by some other author. It gives me errors when i compile it in windows vista environment. I am using Bloodshed Dev C++ v 4.9. please help. #include <iostream.h> #include <map> #include <vector> #include <string> #include <string.h> #include <strstream> #include <unistd.h> #include <stdlib.h> using namespace std; template <class T> class PrefixSpan { private: vector < vector <T> > transaction; vector < pair <T, unsigned int> > pattern; unsigned int minsup; unsigned int minpat; unsigned int maxpat; bool all; bool where; string delimiter; bool verbose; ostream *os; void report (vector <pair <unsigned int, int> > &projected) { if (minpat > pattern.size()) return; // print where & pattern if (where) { *os << "<pattern>" << endl; // what: if (all) { *os << "<freq>" << pattern[pattern.size()-1].second << "</freq>" << endl; *os << "<what>"; for (unsigned int i = 0; i < pattern.size(); i++) *os << (i ? " " : "") << pattern[i].first; } else { *os << "<what>"; for (unsigned int i = 0; i < pattern.size(); i++) *os << (i ? " " : "") << pattern[i].first << delimiter << pattern[i].second; } *os << "</what>" << endl; // where *os << "<where>"; for (unsigned int i = 0; i < projected.size(); i++) *os << (i ? " " : "") << projected[i].first; *os << "</where>" << endl; *os << "</pattern>" << endl; } else { // print found pattern only if (all) { *os << pattern[pattern.size()-1].second; for (unsigned int i = 0; i < pattern.size(); i++) *os << " " << pattern[i].first; } else { for (unsigned int i = 0; i < pattern.size(); i++) *os << (i ? " " : "") << pattern[i].first << delimiter << pattern[i].second; } *os << endl; } } void project (vector <pair <unsigned int, int> > &projected) { if (all) report(projected); map <T, vector <pair <unsigned int, int> > > counter; for (unsigned int i = 0; i < projected.size(); i++) { int pos = projected[i].second; unsigned int id = projected[i].first; unsigned int size = transaction[id].size(); map <T, int> tmp; for (unsigned int j = pos + 1; j < size; j++) { T item = transaction[id][j]; if (tmp.find (item) == tmp.end()) tmp[item] = j ; } for (map <T, int>::iterator k = tmp.begin(); k != tmp.end(); ++k) counter[k->first].push_back (make_pair <unsigned int, int> (id, k->second)); } for (map <T, vector <pair <unsigned int, int> > >::iterator l = counter.begin (); l != counter.end (); ) { if (l->second.size() < minsup) { map <T, vector <pair <unsigned int, int> > >::iterator tmp = l; tmp = l; ++tmp; counter.erase (l); l = tmp; } else { ++l; } } if (! all && counter.size () == 0) { report (projected); return; } for (map <T, vector <pair <unsigned int, int> > >::iterator l = counter.begin (); l != counter.end(); ++l) { if (pattern.size () < maxpat) { pattern.push_back (make_pair <T, unsigned int> (l->first, l->second.size())); project (l->second); pattern.erase (pattern.end()); } } } public: PrefixSpan (unsigned int _minsup = 1, unsigned int _minpat = 1, unsigned int _maxpat = 0xffffffff, bool _all = false, bool _where = false, string _delimiter = "/", bool _verbose = false): minsup(_minsup), minpat (_minpat), maxpat (_maxpat), all(_all), where(_where), delimiter (_delimiter), verbose (_verbose) {}; ~PrefixSpan () {}; istream& read (istream &is) { string line; vector <T> tmp; T item; while (getline (is, line)) { tmp.clear (); istrstream istrs ((char *)line.c_str()); while (istrs >> item) tmp.push_back (item); transaction.push_back (tmp); } return is; } ostream& run (ostream &_os) { os = &_os; if (verbose) *os << transaction.size() << endl; vector <pair <unsigned int, int> > root; for (unsigned int i = 0; i < transaction.size(); i++) root.push_back (make_pair (i, -1)); project (root); return *os; } void clear () { transaction.clear (); pattern.clear (); } }; int main (int argc, char **argv) { extern char *optarg; unsigned int minsup = 1; unsigned int minpat = 1; unsigned int maxpat = 0xffffffff; bool all = false; bool where = false; string delimiter = "/"; bool verbose = false; string type = "string"; int opt; while ((opt = getopt(argc, argv, "awvt:M:m:L:d:")) != -1) { switch(opt) { case 'a': all = true; break; case 'w': where = true; break; case 'v': verbose = true; break; case 'm': minsup = atoi (optarg); break; case 'M': minpat = atoi (optarg); break; case 'L': maxpat = atoi (optarg); break; case 't': type = string (optarg); break; case 'd': delimiter = string (optarg); break; default: cout << "Usage: " << argv[0] << " [-m minsup] [-M minpat] [-L maxpat] [-a] [-w] [-v] [-t type] [-d delimiter] < data .." << endl; return -1; } } if (type == "int") { PrefixSpan<unsigned int> prefixspan (minsup, minpat, maxpat, all, where, delimiter, verbose); prefixspan.read (cin); prefixspan.run (cout); }else if (type == "short") { PrefixSpan<unsigned short> prefixspan (minsup, minpat, maxpat, all, where, delimiter, verbose); prefixspan.read (cin); prefixspan.run (cout); } else if (type == "char") { PrefixSpan<unsigned char> prefixspan (minsup, minpat, maxpat, all, where, delimiter, verbose); prefixspan.read (cin); prefixspan.run (cout); } else if (type == "string") { PrefixSpan<string> prefixspan (minsup, minpat, maxpat, all, where, delimiter, verbose); prefixspan.read (cin); prefixspan.run (cout); } else { cerr << "Unknown Item Type: " << type << " : choose from [string|int|short|char]" << endl; return -1; } return 0; }

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  • Nullpointerexcption & abrupt IOStream closure with inheritence and subclasses

    - by user1401652
    A brief background before so we can communicate on the same wave length. I've had about 8-10 university courses on programming from data structure, to one on all languages, to specific ones such as java & c++. I'm a bit rusty because i usually take 2-3 month breaks from coding. This is a personal project that I started thinking of two years back. Okay down to the details, and a specific question, I'm having problems with my mutator functions. It seems to be that I am trying to access a private variable incorrectly. The question is, am I nesting my classes too much and trying to mutate a base class variable the incorrect way. If so point me in the way of the correct literature, or confirm this is my problem so I can restudy this information. Thanks package GroceryReceiptProgram; import java.io.*; import java.util.Vector; public class Date { private int hour, minute, day, month, year; Date() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What's the hour? (Use 1-24 military notation"); hour = Integer.parseInt(keyboard.readLine()); System.out.println("what's the minute? "); minute = Integer.parseInt(keyboard.readLine()); System.out.println("What's the day of the month?"); day = Integer.parseInt(keyboard.readLine()); System.out.println("Which month of the year is it, use an integer"); month = Integer.parseInt(keyboard.readLine()); System.out.println("What year is it?"); year = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (IOException e) { System.out.println("Yo houston we have a problem"); } } public void setHour(int hour) { this.hour = hour; } public void setHour() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What hour, use military notation?"); this.hour = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getHour() { return hour; } public void setMinute(int minute) { this.minute = minute; } public void setMinute() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What minute?"); this.minute = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ": doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": minute shall not cooperate"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in the setMinute function of the Date class"); } } public int getMinute() { return minute; } public void setDay(int day) { this.day = day; } public void setDay() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What day 0-6?"); this.day = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getDay() { return day; } public void setMonth(int month) { this.month = month; } public void setMonth() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What month 0-11?"); this.month = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getMonth() { return month; } public void setYear(int year) { this.year = year; } public void setYear() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What year?"); this.year = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getYear() { return year; } public void set() { setMinute(); setHour(); setDay(); setMonth(); setYear(); } public Vector<Integer> get() { Vector<Integer> holder = new Vector<Integer>(5); holder.add(hour); holder.add(minute); holder.add(month); holder.add(day); holder.add(year); return holder; } }; That is the Date class obviously, next is the other base class Location. package GroceryReceiptProgram; import java.io.*; import java.util.Vector; public class Location { String streetName, state, city, country; int zipCode, address; Location() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What is the street name"); streetName = keyboard.readLine(); System.out.println("Which state?"); state = keyboard.readLine(); System.out.println("Which city?"); city = keyboard.readLine(); System.out.println("Which country?"); country = keyboard.readLine(); System.out.println("Which zipcode?");//if not u.s. continue around this step zipCode = Integer.parseInt(keyboard.readLine()); System.out.println("What address?"); address = Integer.parseInt(keyboard.readLine()); } catch (IOException e) { System.out.println(e.toString()); } } public void setZipCode(int zipCode) { this.zipCode = zipCode; } public void setZipCode() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What zipCode?"); this.zipCode = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public void set() { setAddress(); setCity(); setCountry(); setState(); setStreetName(); setZipCode(); } public int getZipCode() { return zipCode; } public void setAddress(int address) { this.address = address; } public void setAddress() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.address = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getAddress() { return address; } public void setStreetName(String streetName) { this.streetName = streetName; } public void setStreetName() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.streetName = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getStreetName() { return streetName; } public void setState(String state) { this.state = state; } public void setState() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.state = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getState() { return state; } public void setCity(String city) { this.city = city; } public void setCity() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.city = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getCity() { return city; } public void setCountry(String country) { this.country = country; } public void setCountry() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.country = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getCountry() { return country; } }; their parent(What is the proper name?) class package GroceryReceiptProgram; import java.io.*; public class FoodGroup { private int price, count; private Date purchaseDate, expirationDate; private Location location; private String name; public FoodGroup() { try { setPrice(); setCount(); expirationDate.set(); purchaseDate.set(); location.set(); } catch (NullPointerException e) { System.out.println(e.toString() + ": in the constructor of the FoodGroup class"); } } public void setPrice(int price) { this.price = price; } public void setPrice() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What Price?"); price = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": in the FoodGroup class, setPrice function"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in FoodGroup class. SetPrice()"); } } public int getPrice() { return price; } public void setCount(int count) { this.count = count; } public void setCount() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What count?"); count = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": in the FoodGroup class, setCount()"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in FoodGroup class, setCount"); } } public int getCount() { return count; } public void setName(String name) { this.name = name; } public void setName() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.name = keyboard.readLine(); } catch (IOException e) { System.out.println(e.toString()); } } public String getName() { return name; } public void setLocation(Location location) { this.location = location; } public Location getLocation() { return location; } public void setPurchaseDate(Date purchaseDate) { this.purchaseDate = purchaseDate; } public void setPurchaseDate() { this.purchaseDate.set(); } public Date getPurchaseDate() { return purchaseDate; } public void setExpirationDate(Date expirationDate) { this.expirationDate = expirationDate; } public void setExpirationDate() { this.expirationDate.set(); } public Date getExpirationDate() { return expirationDate; } } and finally the main class, so I can get access to all of this work. package GroceryReceiptProgram; public class NewMain { public static void main(String[] args) { FoodGroup test = new FoodGroup(); } } If anyone is further interested, here is a link the UML for this. https://www.dropbox.com/s/1weigjnxih70tbv/GRP.dia

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  • Windows Phone 7 development: reading RSS feeds

    - by DigiMortal
    One limitation on Windows Phone 7 is related to System.Net namespace classes. There is no convenient way to read data from web. There is no WebClient class. There is no GetResponse() method – we have to do it all asynchronously because compact framework has limited set of classes we can use in our applications to communicate with internet. In this posting I will show you how to read RSS-feeds on Windows Phone 7. NB! This is my draft code and it may contain some design flaws and some questionable solutions. This code is intended to use as test-drive for Windows Phone 7 CTP developer tools and I don’t suppose you are going to use this code in production environment. Current state of my RSS-reader Currently my RSS-reader for Windows Phone 7 is very simple, primitive and uses almost all defaults that come out-of-box with Windows Phone 7 CTP developer tools. My first goal before going on with nicer user interface design was making RSS-reading work because instead of convenient classes from .NET Framework we have to use very limited classes from .NET Framework CE. This is why I took the reading of RSS-feeds as my first task. There are currently more things to solve regarding user-interface. As I am pretty new to all this Silverlight stuff I am not very sure if I can modify default controls easily or should I write my own controls that have better look and that work faster. The image on right shows you how my RSS-reader looks like right now. Upper side of screen is filled with list that shows headlines from this blog. The bottom part of screen is used to show description of selected posting. You can click on the image to see it in original size. In my next posting I will show you some improvements of my RSS-reader user interface that make it look nicer. But currently it is nice enough to make sure that RSS-feeds are read correctly. FeedItem class As this is most straight-forward part of the following code I will show you RSS-feed items class first. I think we have to stop on it because it is simple one. public class FeedItem {     public string Title { get; set; }     public string Description { get; set; }     public DateTime PublishDate { get; set; }     public List<string> Categories { get; set; }     public string Link { get; set; }       public FeedItem()     {         Categories = new List<string>();     } } RssClient RssClient takes feed URL and when asked it loads all items from feed and gives them back to caller through ItemsReceived event. Why it works this way? Because we can make responses only using asynchronous methods. I will show you in next section how to use this class. Although the code here is not very good but it works like expected. I will refactor this code later because it needs some more efforts and investigating. But let’s hope I find excellent solution. :) public class RssClient {     private readonly string _rssUrl;       public delegate void ItemsReceivedDelegate(RssClient client, IList<FeedItem> items);     public event ItemsReceivedDelegate ItemsReceived;       public RssClient(string rssUrl)     {         _rssUrl = rssUrl;     }       public void LoadItems()     {         var request = (HttpWebRequest)WebRequest.Create(_rssUrl);         var result = (IAsyncResult)request.BeginGetResponse(ResponseCallback, request);     }       void ResponseCallback(IAsyncResult result)     {         var request = (HttpWebRequest)result.AsyncState;         var response = request.EndGetResponse(result);           var stream = response.GetResponseStream();         var reader = XmlReader.Create(stream);         var items = new List<FeedItem>(50);           FeedItem item = null;         var pointerMoved = false;           while (!reader.EOF)         {             if (pointerMoved)             {                 pointerMoved = false;             }             else             {                 if (!reader.Read())                     break;             }               var nodeName = reader.Name;             var nodeType = reader.NodeType;               if (nodeName == "item")             {                 if (nodeType == XmlNodeType.Element)                     item = new FeedItem();                 else if (nodeType == XmlNodeType.EndElement)                     if (item != null)                     {                         items.Add(item);                         item = null;                     }                   continue;             }               if (nodeType != XmlNodeType.Element)                 continue;               if (item == null)                 continue;               reader.MoveToContent();             var nodeValue = reader.ReadElementContentAsString();             // we just moved internal pointer             pointerMoved = true;               if (nodeName == "title")                 item.Title = nodeValue;             else if (nodeName == "description")                 item.Description =  Regex.Replace(nodeValue,@"<(.|\n)*?>",string.Empty);             else if (nodeName == "feedburner:origLink")                 item.Link = nodeValue;             else if (nodeName == "pubDate")             {                 if (!string.IsNullOrEmpty(nodeValue))                     item.PublishDate = DateTime.Parse(nodeValue);             }             else if (nodeName == "category")                 item.Categories.Add(nodeValue);         }           if (ItemsReceived != null)             ItemsReceived(this, items);     } } This method is pretty long but it works. Now let’s try to use it in Windows Phone 7 application. Using RssClient And this is the fragment of code behing the main page of my application start screen. You can see how RssClient is initialized and how items are bound to list that shows them. public MainPage() {     InitializeComponent();       SupportedOrientations = SupportedPageOrientation.Portrait | SupportedPageOrientation.Landscape;     listBox1.Width = Width;       var rssClient = new RssClient("http://feedproxy.google.com/gunnarpeipman");     rssClient.ItemsReceived += new RssClient.ItemsReceivedDelegate(rssClient_ItemsReceived);     rssClient.LoadItems(); }   void rssClient_ItemsReceived(RssClient client, IList<FeedItem> items) {     Dispatcher.BeginInvoke(delegate()     {         listBox1.ItemsSource = items;     });            } Conclusion As you can see it was not very hard task to read RSS-feed and populate list with feed entries. Although we are not able to use more powerful classes that are part of full version on .NET Framework we can still live with limited set of classes that .NET Framework CE provides.

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  • Windows Phone 7: Building a simple dictionary web client

    - by TechTwaddle
    Like I mentioned in this post a while back, I came across a dictionary web service called Aonaware that serves up word definitions from various dictionaries and is really easy to use. The services page on their website, http://services.aonaware.com/DictService/DictService.asmx, lists all the operations that are supported by the dictionary service. Here they are, Word Dictionary Web Service The following operations are supported. For a formal definition, please review the Service Description. Define Define given word, returning definitions from all dictionaries DefineInDict Define given word, returning definitions from specified dictionary DictionaryInfo Show information about the specified dictionary DictionaryList Returns a list of available dictionaries DictionaryListExtended Returns a list of advanced dictionaries (e.g. translating dictionaries) Match Look for matching words in all dictionaries using the given strategy MatchInDict Look for matching words in the specified dictionary using the given strategy ServerInfo Show remote server information StrategyList Return list of all available strategies on the server Follow the links above to get more information on each API. In this post we will be building a simple windows phone 7 client which uses this service to get word definitions for words entered by the user. The application will also allow the user to select a dictionary from all the available ones and look up the word definition in that dictionary. So of all the apis above we will be using only two, DictionaryList() to get a list of all supported dictionaries and DefineInDict() to get the word definition from a particular dictionary. Before we get started, a note to you all; I would have liked to implement this application using concepts from data binding, item templates, data templates etc. I have a basic understanding of what they are but, being a beginner, I am not very comfortable with those topics yet so I didn’t use them. I thought I’ll get this version out of the way and maybe in the next version I could give those a try. A somewhat scary mock-up of the what the final application will look like, Select Dictionary is a list picker control from the silverlight toolkit (you need to download and install the toolkit if you haven’t already). Below it is a textbox where the user can enter words to look up and a button beside it to fetch the word definition when clicked. Finally we have a textblock which occupies the remaining area and displays the word definition from the selected dictionary. Create a silverlight application for windows phone 7, AonawareDictionaryClient, and add references to the silverlight toolkit and the web service. From the solution explorer right on References and select Microsoft.Phone.Controls.Toolkit from under the .NET tab, Next, add a reference to the web service. Again right click on References and this time select Add Service Reference In the resulting dialog paste the service url in the Address field and press go, (url –> http://services.aonaware.com/DictService/DictService.asmx) once the service is discovered, provide a name for the NameSpace, in this case I’ve called it AonawareDictionaryService. Press OK. You can now use the classes and functions that are generated in the AonawareDictionaryClient.AonawareDictionaryService namespace. Let’s get the UI done now. In MainPage.xaml add a namespace declaration to use the toolkit controls, xmlns:toolkit="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone.Controls.Toolkit" the content of LayoutRoot is changed as follows, (sorry, no syntax highlighting in this post) <StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,5,0,5">     <TextBlock x:Name="ApplicationTitle" Text="AONAWARE DICTIONARY CLIENT" Style="{StaticResource PhoneTextNormalStyle}"/>     <!--<TextBlock x:Name="PageTitle" Text="page name" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>--> </StackPanel> <!--ContentPanel - place additional content here--> <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">     <Grid.RowDefinitions>         <RowDefinition Height="Auto"/>         <RowDefinition Height="Auto"/>         <RowDefinition Height="*"/>     </Grid.RowDefinitions>     <toolkit:ListPicker Grid.Column="1" x:Name="listPickerDictionaryList"                         Header="Select Dictionary :">     </toolkit:ListPicker>     <Grid Grid.Row="1" Margin="0,5,0,0">         <Grid.ColumnDefinitions>             <ColumnDefinition Width="*"/>             <ColumnDefinition Width="Auto" />         </Grid.ColumnDefinitions>         <TextBox x:Name="txtboxInputWord" Grid.Column="0" GotFocus="OnTextboxInputWordGotFocus" />         <Button x:Name="btnGo" Grid.Column="1" Click="OnButtonGoClick" >             <Button.Content>                 <Image Source="/images/button-go.png"/>             </Button.Content>         </Button>     </Grid>     <ScrollViewer Grid.Row="2" x:Name="scrollViewer">         <TextBlock  Margin="12,5,12,5"  x:Name="txtBlockWordMeaning" HorizontalAlignment="Stretch"                    VerticalAlignment="Stretch" TextWrapping="Wrap"                    FontSize="26" />     </ScrollViewer> </Grid> I have commented out the PageTitle as it occupies too much valuable space, and the ContentPanel is changed to contain three rows. First row contains the list picker control, second row contains the textbox and the button, and the third row contains a textblock within a scroll viewer. The designer will now be showing the final ui, Now go to MainPage.xaml.cs, and add the following namespace declarations, using Microsoft.Phone.Controls; using AonawareDictionaryClient.AonawareDictionaryService; using System.IO.IsolatedStorage; A class called DictServiceSoapClient would have been created for you in the background when you added a reference to the web service. This class functions as a wrapper to the services exported by the web service. All the web service functions that we saw at the start can be access through this class, or more precisely through an object of this class. Create a data member of type DictServiceSoapClient in the Mainpage class, and a function which initializes it, DictServiceSoapClient DictSvcClient = null; private DictServiceSoapClient GetDictServiceSoapClient() {     if (null == DictSvcClient)     {         DictSvcClient = new DictServiceSoapClient();     }     return DictSvcClient; } We have two major tasks remaining. First, when the application loads we need to populate the list picker with all the supported dictionaries and second, when the user enters a word and clicks on the arrow button we need to fetch the word’s meaning. Populating the List Picker In the OnNavigatingTo event of the MainPage, we call the DictionaryList() api. This can also be done in the OnLoading event handler of the MainPage; not sure if one has an advantage over the other. Here’s the code for OnNavigatedTo, protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e) {     DictServiceSoapClient client = GetDictServiceSoapClient();     client.DictionaryListCompleted += new EventHandler<DictionaryListCompletedEventArgs>(OnGetDictionaryListCompleted);     client.DictionaryListAsync();     base.OnNavigatedTo(e); } Windows Phone 7 supports only async calls to web services. When we added a reference to the dictionary service, asynchronous versions of all the functions were generated automatically. So in the above function we register a handler to the DictionaryListCompleted event which will occur when the call to DictionaryList() gets a response from the server. Then we call the DictionaryListAsynch() function which is the async version of the DictionaryList() api. The result of this api will be sent to the handler OnGetDictionaryListCompleted(), void OnGetDictionaryListCompleted(object sender, DictionaryListCompletedEventArgs e) {     IsolatedStorageSettings settings = IsolatedStorageSettings.ApplicationSettings;     Dictionary[] listOfDictionaries;     if (e.Error == null)     {         listOfDictionaries = e.Result;         PopulateListPicker(listOfDictionaries, settings);     }     else if (settings.Contains("SavedDictionaryList"))     {         listOfDictionaries = settings["SavedDictionaryList"] as Dictionary[];         PopulateListPicker(listOfDictionaries, settings);     }     else     {         MessageBoxResult res = MessageBox.Show("An error occured while retrieving dictionary list, do you want to try again?", "Error", MessageBoxButton.OKCancel);         if (MessageBoxResult.OK == res)         {             GetDictServiceSoapClient().DictionaryListAsync();         }     }     settings.Save(); } I have used IsolatedStorageSettings to store a few things; the entire dictionary list and the dictionary that is selected when the user exits the application, so that the next time when the user starts the application the current dictionary is set to the last selected value. First we check if the api returned any error, if the error object is null e.Result will contain the list (actually array) of Dictionary type objects. If there was an error, we check the isolated storage settings to see if there is a dictionary list stored from a previous instance of the application and if so, we populate the list picker based on this saved list. Note that in this case there are chances that the dictionary list might be out of date if there have been changes on the server. Finally, if none of these cases are true, we display an error message to the user and try to fetch the list again. PopulateListPicker() is passed the array of Dictionary objects and the settings object as well, void PopulateListPicker(Dictionary[] listOfDictionaries, IsolatedStorageSettings settings) {     listPickerDictionaryList.Items.Clear();     foreach (Dictionary dictionary in listOfDictionaries)     {         listPickerDictionaryList.Items.Add(dictionary.Name);     }     settings["SavedDictionaryList"] = listOfDictionaries;     string savedDictionaryName;     if (settings.Contains("SavedDictionary"))     {         savedDictionaryName = settings["SavedDictionary"] as string;     }     else     {         savedDictionaryName = "WordNet (r) 2.0"; //default dictionary, wordnet     }     foreach (string dictName in listPickerDictionaryList.Items)     {         if (dictName == savedDictionaryName)         {             listPickerDictionaryList.SelectedItem = dictName;             break;         }     }     settings["SavedDictionary"] = listPickerDictionaryList.SelectedItem as string; } We first clear all the items from the list picker, add the dictionary names from the array and then create a key in the settings called SavedDictionaryList and store the dictionary list in it. We then check if there is saved dictionary available from a previous instance, if there is, we set it as the selected item in the list picker. And if not, we set “WordNet ® 2.0” as the default dictionary. Before returning, we save the selected dictionary in the “SavedDictionary” key of the isolated storage settings. Fetching word definitions Getting this part done is very similar to the above code. We get the input word from the textbox, call into DefineInDictAsync() to fetch the definition and when DefineInDictAsync completes, we get the result and display it in the textblock. Here is the handler for the button click, private void OnButtonGoClick(object sender, RoutedEventArgs e) {     txtBlockWordMeaning.Text = "Please wait..";     IsolatedStorageSettings settings = IsolatedStorageSettings.ApplicationSettings;     if (txtboxInputWord.Text.Trim().Length <= 0)     {         MessageBox.Show("Please enter a word in the textbox and press 'Go'");     }     else     {         Dictionary[] listOfDictionaries = settings["SavedDictionaryList"] as Dictionary[];         string selectedDictionary = listPickerDictionaryList.SelectedItem.ToString();         string dictId = "wn"; //default dictionary is wordnet (wn is the dict id)         foreach (Dictionary dict in listOfDictionaries)         {             if (dict.Name == selectedDictionary)             {                 dictId = dict.Id;                 break;             }         }         DictServiceSoapClient client = GetDictServiceSoapClient();         client.DefineInDictCompleted += new EventHandler<DefineInDictCompletedEventArgs>(OnDefineInDictCompleted);         client.DefineInDictAsync(dictId, txtboxInputWord.Text.Trim());     } } We validate the input and then select the dictionary id based on the currently selected dictionary. We need the dictionary id because the api DefineInDict() expects the dictionary identifier and not the dictionary name. We could very well have stored the dictionary id in isolated storage settings too. Again, same as before, we register a event handler for the DefineInDictCompleted event and call the DefineInDictAsync() method passing in the dictionary id and the input word. void OnDefineInDictCompleted(object sender, DefineInDictCompletedEventArgs e) {     WordDefinition wd = e.Result;     scrollViewer.ScrollToVerticalOffset(0.0f);     if (wd.Definitions.Length == 0)     {         txtBlockWordMeaning.Text = String.Format("No definitions were found for '{0}' in '{1}'", txtboxInputWord.Text.Trim(), listPickerDictionaryList.SelectedItem.ToString().Trim());     }     else     {         foreach (Definition def in wd.Definitions)         {             string str = def.WordDefinition;             str = str.Replace("  ", " "); //some formatting             txtBlockWordMeaning.Text = str;         }     } } When the api completes, e.Result will contain a WordDefnition object. This class is also generated in the background while adding the service reference. We check the word definitions within this class to see if any results were returned, if not, we display a message to the user in the textblock. If a definition was found the text on the textblock is set to display the definition of the word. Adding final touches, we now need to save the current dictionary when the application exits. A small but useful thing is selecting the entire word in the input textbox when the user selects it. This makes sure that if the user has looked up a definition for a really long word, he doesn’t have to press ‘clear’ too many times to enter the next word, protected override void OnNavigatingFrom(System.Windows.Navigation.NavigatingCancelEventArgs e) {     IsolatedStorageSettings settings = IsolatedStorageSettings.ApplicationSettings;     settings["SavedDictionary"] = listPickerDictionaryList.SelectedItem as string;     settings.Save();     base.OnNavigatingFrom(e); } private void OnTextboxInputWordGotFocus(object sender, RoutedEventArgs e) {     TextBox txtbox = sender as TextBox;     if (txtbox.Text.Trim().Length > 0)     {         txtbox.SelectionStart = 0;         txtbox.SelectionLength = txtbox.Text.Length;     } } OnNavigatingFrom() is called whenever you navigate away from the MainPage, since our application contains only one page that would mean that it is exiting. I leave you with a short video of the application in action, but before that if you have any suggestions on how to make the code better and improve it please do leave a comment. Until next time…

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  • Windows Azure Service Bus Scatter-Gather Implementation

    - by Alan Smith
    One of the more challenging enterprise integration patterns that developers may wish to implement is the Scatter-Gather pattern. In this article I will show the basic implementation of a scatter-gather pattern using the topic-subscription model of the windows azure service bus. I’ll be using the implementation in demos, and also as a lab in my training courses, and the pattern will also be included in the next release of my free e-book the “Windows Azure Service Bus Developer Guide”. The Scatter-Gather pattern answers the following scenario. How do you maintain the overall message flow when a message needs to be sent to multiple recipients, each of which may send a reply? Use a Scatter-Gather that broadcasts a message to multiple recipients and re-aggregates the responses back into a single message. The Enterprise Integration Patterns website provides a description of the Scatter-Gather pattern here.   The scatter-gather pattern uses a composite of the publish-subscribe channel pattern and the aggregator pattern. The publish-subscribe channel is used to broadcast messages to a number of receivers, and the aggregator is used to gather the response messages and aggregate them together to form a single message. Scatter-Gather Scenario The scenario for this scatter-gather implementation is an application that allows users to answer questions in a poll based voting scenario. A poll manager application will be used to broadcast questions to users, the users will use a voting application that will receive and display the questions and send the votes back to the poll manager. The poll manager application will receive the users’ votes and aggregate them together to display the results. The scenario should be able to scale to support a large number of users.   Scatter-Gather Implementation The diagram below shows the overall architecture for the scatter-gather implementation.       Messaging Entities Looking at the scatter-gather pattern diagram it can be seen that the topic-subscription architecture is well suited for broadcasting a message to a number of subscribers. The poll manager application can send the question messages to a topic, and each voting application can receive the question message on its own subscription. The static limit of 2,000 subscriptions per topic in the current release means that 2,000 voting applications can receive question messages and take part in voting. The vote messages can then be sent to the poll manager application using a queue. The voting applications will send their vote messages to the queue, and the poll manager will receive and process the vote messages. The questions topic and answer queue are created using the Windows Azure Developer Portal. Each instance of the voting application will create its own subscription in the questions topic when it starts, allowing the question messages to be broadcast to all subscribing voting applications. Data Contracts Two simple data contracts will be used to serialize the questions and votes as brokered messages. The code for these is shown below.   [DataContract] public class Question {     [DataMember]     public string QuestionText { get; set; } }     To keep the implementation of the voting functionality simple and focus on the pattern implementation, the users can only vote yes or no to the questions.   [DataContract] public class Vote {     [DataMember]     public string QuestionText { get; set; }       [DataMember]     public bool IsYes { get; set; } }     Poll Manager Application The poll manager application has been implemented as a simple WPF application; the user interface is shown below. A question can be entered in the text box, and sent to the topic by clicking the Add button. The topic and subscriptions used for broadcasting the messages are shown in a TreeView control. The questions that have been broadcast and the resulting votes are shown in a ListView control. When the application is started any existing subscriptions are cleared form the topic, clients are then created for the questions topic and votes queue, along with background workers for receiving and processing the vote messages, and updating the display of subscriptions.   public MainWindow() {     InitializeComponent();       // Create a new results list and data bind it.     Results = new ObservableCollection<Result>();     lsvResults.ItemsSource = Results;       // Create a token provider with the relevant credentials.     TokenProvider credentials =         TokenProvider.CreateSharedSecretTokenProvider         (AccountDetails.Name, AccountDetails.Key);       // Create a URI for the serivce bus.     Uri serviceBusUri = ServiceBusEnvironment.CreateServiceUri         ("sb", AccountDetails.Namespace, string.Empty);       // Clear out any old subscriptions.     NamespaceManager = new NamespaceManager(serviceBusUri, credentials);     IEnumerable<SubscriptionDescription> subs =         NamespaceManager.GetSubscriptions(AccountDetails.ScatterGatherTopic);     foreach (SubscriptionDescription sub in subs)     {         NamespaceManager.DeleteSubscription(sub.TopicPath, sub.Name);     }       // Create the MessagingFactory     MessagingFactory factory = MessagingFactory.Create(serviceBusUri, credentials);       // Create the topic and queue clients.     ScatterGatherTopicClient =         factory.CreateTopicClient(AccountDetails.ScatterGatherTopic);     ScatterGatherQueueClient =         factory.CreateQueueClient(AccountDetails.ScatterGatherQueue);       // Start the background worker threads.     VotesBackgroundWorker = new BackgroundWorker();     VotesBackgroundWorker.DoWork += new DoWorkEventHandler(ReceiveMessages);     VotesBackgroundWorker.RunWorkerAsync();       SubscriptionsBackgroundWorker = new BackgroundWorker();     SubscriptionsBackgroundWorker.DoWork += new DoWorkEventHandler(UpdateSubscriptions);     SubscriptionsBackgroundWorker.RunWorkerAsync(); }     When the poll manager user nters a question in the text box and clicks the Add button a question message is created and sent to the topic. This message will be broadcast to all the subscribing voting applications. An instance of the Result class is also created to keep track of the votes cast, this is then added to an observable collection named Results, which is data-bound to the ListView control.   private void btnAddQuestion_Click(object sender, RoutedEventArgs e) {     // Create a new result for recording votes.     Result result = new Result()     {         Question = txtQuestion.Text     };     Results.Add(result);       // Send the question to the topic     Question question = new Question()     {         QuestionText = result.Question     };     BrokeredMessage msg = new BrokeredMessage(question);     ScatterGatherTopicClient.Send(msg);       txtQuestion.Text = ""; }     The Results class is implemented as follows.   public class Result : INotifyPropertyChanged {     public string Question { get; set; }       private int m_YesVotes;     private int m_NoVotes;       public event PropertyChangedEventHandler PropertyChanged;       public int YesVotes     {         get { return m_YesVotes; }         set         {             m_YesVotes = value;             NotifyPropertyChanged("YesVotes");         }     }       public int NoVotes     {         get { return m_NoVotes; }         set         {             m_NoVotes = value;             NotifyPropertyChanged("NoVotes");         }     }       private void NotifyPropertyChanged(string prop)     {         if(PropertyChanged != null)         {             PropertyChanged(this, new PropertyChangedEventArgs(prop));         }     } }     The INotifyPropertyChanged interface is implemented so that changes to the number of yes and no votes will be updated in the ListView control. Receiving the vote messages from the voting applications is done asynchronously, using a background worker thread.   // This runs on a background worker. private void ReceiveMessages(object sender, DoWorkEventArgs e) {     while (true)     {         // Receive a vote message from the queue         BrokeredMessage msg = ScatterGatherQueueClient.Receive();         if (msg != null)         {             // Deserialize the message.             Vote vote = msg.GetBody<Vote>();               // Update the results.             foreach (Result result in Results)             {                 if (result.Question.Equals(vote.QuestionText))                 {                     if (vote.IsYes)                     {                         result.YesVotes++;                     }                     else                     {                         result.NoVotes++;                     }                     break;                 }             }               // Mark the message as complete.             msg.Complete();         }       } }     When a vote message is received, the result that matches the vote question is updated with the vote from the user. The message is then marked as complete. A second background thread is used to update the display of subscriptions in the TreeView, with a dispatcher used to update the user interface. // This runs on a background worker. private void UpdateSubscriptions(object sender, DoWorkEventArgs e) {     while (true)     {         // Get a list of subscriptions.         IEnumerable<SubscriptionDescription> subscriptions =             NamespaceManager.GetSubscriptions(AccountDetails.ScatterGatherTopic);           // Update the user interface.         SimpleDelegate setQuestion = delegate()         {             trvSubscriptions.Items.Clear();             TreeViewItem topicItem = new TreeViewItem()             {                 Header = AccountDetails.ScatterGatherTopic             };               foreach (SubscriptionDescription subscription in subscriptions)             {                 TreeViewItem subscriptionItem = new TreeViewItem()                 {                     Header = subscription.Name                 };                 topicItem.Items.Add(subscriptionItem);             }             trvSubscriptions.Items.Add(topicItem);               topicItem.ExpandSubtree();         };         this.Dispatcher.BeginInvoke(DispatcherPriority.Send, setQuestion);           Thread.Sleep(3000);     } }       Voting Application The voting application is implemented as another WPF application. This one is more basic, and allows the user to vote “Yes” or “No” for the questions sent by the poll manager application. The user interface for that application is shown below. When an instance of the voting application is created it will create a subscription in the questions topic using a GUID as the subscription name. The application can then receive copies of every question message that is sent to the topic. Clients for the new subscription and the votes queue are created, along with a background worker to receive the question messages. The voting application is set to receiving mode, meaning it is ready to receive a question message from the subscription.   public MainWindow() {     InitializeComponent();       // Set the mode to receiving.     IsReceiving = true;       // Create a token provider with the relevant credentials.     TokenProvider credentials =         TokenProvider.CreateSharedSecretTokenProvider         (AccountDetails.Name, AccountDetails.Key);       // Create a URI for the serivce bus.     Uri serviceBusUri = ServiceBusEnvironment.CreateServiceUri         ("sb", AccountDetails.Namespace, string.Empty);       // Create the MessagingFactory     MessagingFactory factory = MessagingFactory.Create(serviceBusUri, credentials);       // Create a subcription for this instance     NamespaceManager mgr = new NamespaceManager(serviceBusUri, credentials);     string subscriptionName = Guid.NewGuid().ToString();     mgr.CreateSubscription(AccountDetails.ScatterGatherTopic, subscriptionName);       // Create the subscription and queue clients.     ScatterGatherSubscriptionClient = factory.CreateSubscriptionClient         (AccountDetails.ScatterGatherTopic, subscriptionName);     ScatterGatherQueueClient =         factory.CreateQueueClient(AccountDetails.ScatterGatherQueue);       // Start the background worker thread.     BackgroundWorker = new BackgroundWorker();     BackgroundWorker.DoWork += new DoWorkEventHandler(ReceiveMessages);     BackgroundWorker.RunWorkerAsync(); }     I took the inspiration for creating the subscriptions in the voting application from the chat application that uses topics and subscriptions blogged by Ovais Akhter here. The method that receives the question messages runs on a background thread. If the application is in receive mode, a question message will be received from the subscription, the question will be displayed in the user interface, the voting buttons enabled, and IsReceiving set to false to prevent more questing from being received before the current one is answered.   // This runs on a background worker. private void ReceiveMessages(object sender, DoWorkEventArgs e) {     while (true)     {         if (IsReceiving)         {             // Receive a question message from the topic.             BrokeredMessage msg = ScatterGatherSubscriptionClient.Receive();             if (msg != null)             {                 // Deserialize the message.                 Question question = msg.GetBody<Question>();                   // Update the user interface.                 SimpleDelegate setQuestion = delegate()                 {                     lblQuestion.Content = question.QuestionText;                     btnYes.IsEnabled = true;                     btnNo.IsEnabled = true;                 };                 this.Dispatcher.BeginInvoke(DispatcherPriority.Send, setQuestion);                 IsReceiving = false;                   // Mark the message as complete.                 msg.Complete();             }         }         else         {             Thread.Sleep(1000);         }     } }     When the user clicks on the Yes or No button, the btnVote_Click method is called. This will create a new Vote data contract with the appropriate question and answer and send the message to the poll manager application using the votes queue. The user voting buttons are then disabled, the question text cleared, and the IsReceiving flag set to true to allow a new message to be received.   private void btnVote_Click(object sender, RoutedEventArgs e) {     // Create a new vote.     Vote vote = new Vote()     {         QuestionText = (string)lblQuestion.Content,         IsYes = ((sender as Button).Content as string).Equals("Yes")     };       // Send the vote message.     BrokeredMessage msg = new BrokeredMessage(vote);     ScatterGatherQueueClient.Send(msg);       // Update the user interface.     lblQuestion.Content = "";     btnYes.IsEnabled = false;     btnNo.IsEnabled = false;     IsReceiving = true; }     Testing the Application In order to test the application, an instance of the poll manager application is started; the user interface is shown below. As no instances of the voting application have been created there are no subscriptions present in the topic. When an instance of the voting application is created the subscription will be displayed in the poll manager. Now that a voting application is subscribing, a questing can be sent from the poll manager application. When the message is sent to the topic, the voting application will receive the message and display the question. The voter can then answer the question by clicking on the appropriate button. The results of the vote are updated in the poll manager application. When two more instances of the voting application are created, the poll manager will display the new subscriptions. More questions can then be broadcast to the voting applications. As the question messages are queued up in the subscription for each voting application, the users can answer the questions in their own time. The vote messages will be received by the poll manager application and aggregated to display the results. The screenshots of the applications part way through voting are shown below. The messages for each voting application are queued up in sequence on the voting application subscriptions, allowing the questions to be answered at different speeds by the voters.

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  • From HttpRuntime.Cache to Windows Azure Caching (Preview)

    - by Jeff
    I don’t know about you, but the announcement of Windows Azure Caching (Preview) (yes, the parentheses are apparently part of the interim name) made me a lot more excited about using Azure. Why? Because one of the great performance tricks of any Web app is to cache frequently used data in memory, so it doesn’t have to hit the database, a service, or whatever. When you run your Web app on one box, HttpRuntime.Cache is a sweet and stupid-simple solution. Somewhere in the data fetching pieces of your app, you can see if an object is available in cache, and return that instead of hitting the data store. I did this quite a bit in POP Forums, and it dramatically cuts down on the database chatter. The problem is that it falls apart if you run the app on many servers, in a Web farm, where one server may initiate a change to that data, and the others will have no knowledge of the change, making it stale. Of course, if you have the infrastructure to do so, you can use something like memcached or AppFabric to do a distributed cache, and achieve the caching flavor you desire. You could do the same thing in Azure before, but it would cost more because you’d need to pay for another role or VM or something to host the cache. Now, you can use a portion of the memory from each instance of a Web role to act as that cache, with no additional cost. That’s huge. So if you’re using a percentage of memory that comes out to 100 MB, and you have three instances running, that’s 300 MB available for caching. For the uninitiated, a Web role in Azure is essentially a VM that runs a Web app (worker roles are the same idea, only without the IIS part). You can spin up many instances of the role, and traffic is load balanced to the various instances. It’s like adding or removing servers to a Web farm all willy-nilly and at your discretion, and it’s what the cloud is all about. I’d say it’s my favorite thing about Windows Azure. The slightly annoying thing about developing for a Web role in Azure is that the local emulator that’s launched by Visual Studio is a little on the slow side. If you’re used to using the built-in Web server, you’re used to building and then alt-tabbing to your browser and refreshing a page. If you’re just changing an MVC view, you’re not even doing the building part. Spinning up the simulated Azure environment is too slow for this, but ideally you want to code your app to use this fantastic distributed cache mechanism. So first off, here’s the link to the page showing how to code using the caching feature. If you’re used to using HttpRuntime.Cache, this should be pretty familiar to you. Let’s say that you want to use the Azure cache preview when you’re running in Azure, but HttpRuntime.Cache if you’re running local, or in a regular IIS server environment. Through the magic of dependency injection, we can get there pretty quickly. First, design an interface to handle the cache insertion, fetching and removal. Mine looks like this: public interface ICacheProvider {     void Add(string key, object item, int duration);     T Get<T>(string key) where T : class;     void Remove(string key); } Now we’ll create two implementations of this interface… one for Azure cache, one for HttpRuntime: public class AzureCacheProvider : ICacheProvider {     public AzureCacheProvider()     {         _cache = new DataCache("default"); // in Microsoft.ApplicationServer.Caching, see how-to      }         private readonly DataCache _cache;     public void Add(string key, object item, int duration)     {         _cache.Add(key, item, new TimeSpan(0, 0, 0, 0, duration));     }     public T Get<T>(string key) where T : class     {         return _cache.Get(key) as T;     }     public void Remove(string key)     {         _cache.Remove(key);     } } public class LocalCacheProvider : ICacheProvider {     public LocalCacheProvider()     {         _cache = HttpRuntime.Cache;     }     private readonly System.Web.Caching.Cache _cache;     public void Add(string key, object item, int duration)     {         _cache.Insert(key, item, null, DateTime.UtcNow.AddMilliseconds(duration), System.Web.Caching.Cache.NoSlidingExpiration);     }     public T Get<T>(string key) where T : class     {         return _cache[key] as T;     }     public void Remove(string key)     {         _cache.Remove(key);     } } Feel free to expand these to use whatever cache features you want. I’m not going to go over dependency injection here, but I assume that if you’re using ASP.NET MVC, you’re using it. Somewhere in your app, you set up the DI container that resolves interfaces to concrete implementations (Ninject call is a “kernel” instead of a container). For this example, I’ll show you how StructureMap does it. It uses a convention based scheme, where if you need to get an instance of IFoo, it looks for a class named Foo. You can also do this mapping explicitly. The initialization of the container looks something like this: ObjectFactory.Initialize(x =>             {                 x.Scan(scan =>                         {                             scan.AssembliesFromApplicationBaseDirectory();                             scan.WithDefaultConventions();                         });                 if (Microsoft.WindowsAzure.ServiceRuntime.RoleEnvironment.IsAvailable)                     x.For<ICacheProvider>().Use<AzureCacheProvider>();                 else                     x.For<ICacheProvider>().Use<LocalCacheProvider>();             }); If you use Ninject or Windsor or something else, that’s OK. Conceptually they’re all about the same. The important part is the conditional statement that checks to see if the app is running in Azure. If it is, it maps ICacheProvider to AzureCacheProvider, otherwise it maps to LocalCacheProvider. Now when a request comes into your MVC app, and the chain of dependency resolution occurs, you can see to it that the right caching code is called. A typical design may have a call stack that goes: Controller –> BusinessLogicClass –> Repository. Let’s say your repository class looks like this: public class MyRepo : IMyRepo {     public MyRepo(ICacheProvider cacheProvider)     {         _context = new MyDataContext();         _cache = cacheProvider;     }     private readonly MyDataContext _context;     private readonly ICacheProvider _cache;     public SomeType Get(int someTypeID)     {         var key = "somename-" + someTypeID;         var cachedObject = _cache.Get<SomeType>(key);         if (cachedObject != null)         {             _context.SomeTypes.Attach(cachedObject);             return cachedObject;         }         var someType = _context.SomeTypes.SingleOrDefault(p => p.SomeTypeID == someTypeID);         _cache.Add(key, someType, 60000);         return someType;     } ... // more stuff to update, delete or whatever, being sure to remove // from cache when you do so  When the DI container gets an instance of the repo, it passes an instance of ICacheProvider to the constructor, which in this case will be whatever implementation was specified when the container was initialized. The Get method first tries to hit the cache, and of course doesn’t care what the underlying implementation is, Azure, HttpRuntime, or otherwise. If it finds the object, it returns it right then. If not, it hits the database (this example is using Entity Framework), and inserts the object into the cache before returning it. The important thing not pictured here is that other methods in the repo class will construct the key for the cached object, in this case “somename-“ plus the ID of the object, and then remove it from cache, in any method that alters or deletes the object. That way, no matter what instance of the role is processing the request, it won’t find the object if it has been made stale, that is, updated or outright deleted, forcing it to attempt to hit the database. So is this good technique? Well, sort of. It depends on how you use it, and what your testing looks like around it. Because of differences in behavior and execution of the two caching providers, for example, you could see some strange errors. For example, I immediately got an error indicating there was no parameterless constructor for an MVC controller, because the DI resolver failed to create instances for the dependencies it had. In reality, the NuGet packaged DI resolver for StructureMap was eating an exception thrown by the Azure components that said my configuration, outlined in that how-to article, was wrong. That error wouldn’t occur when using the HttpRuntime. That’s something a lot of people debate about using different components like that, and how you configure them. I kinda hate XML config files, and like the idea of the code-based approach above, but you should be darn sure that your unit and integration testing can account for the differences.

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