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  • Null Value Statement

    - by Sam
    Hi All, I have created a table called table1 and it has 4 columns named Name,ID,Description and Date. I have created them like Name varchar(50) null, ID int null,Description varchar(50) null, Date datetime null I have inserted a record into the table1 having ID and Description values. So Now my table1 looks like this: Name ID Description Date Null 1 First Null One of them asked me to modify the table such a way that The columns Name and Date should have Null values instead of Text Null. I don't know what is the difference between those I mean can anyone explain me the difference between these select statements: SELECT * FROM TABLE1 WHERE NAME IS NULL SELECT * FROM TABLE1 WHERE NAME = 'NULL' SELECT * FROM TABLE1 WHERE NAME = ' ' Can anyone explain me?

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  • Specifying $(this).val() for two different elements (by class)

    - by Chaya Cooper
    What would be the correct syntax for specifying 2 elements by class to evaluate their values when they have different classes? This snippet adds and/or removes values from "increase_priority1" when the user has selected both a complaint and ranked the importance level of the issue, however when I added the 2nd element (".complaint select") to the If Statement it stopped working properly and only accepts input from the 2nd item (Waist) after the 1rst item (Shoulders) has been selected. I believe the problem is that it's unable to determine which ".complaint select" to use, but I haven't been able to figure out how to use (this) for the 2nd element, or another similar approach. The complete function includes apx. 20 similar pairs of If Statements to set & unset other elements, and a working example with 4 pairs is available at http://jsfiddle.net/chayacooper/vWLEn/168/ I'm trying to avoid using ID's because that becomes pretty cumbersome to do for 25 Select elements and each of their values (ID's were also problematic because it stopped working when I added a 2nd element to the If Statement for removing/unsetting a value) Javascript var $increase_priority1 = $(".increase_priority1"); // If value is "Shoulders", complaint was Shoulders too small (select name=Shoulders value=Too_small) and it was assigned a level 1 priority (select class="ranking shoulders" value=1). // var's for other issues and priority levels go here $(".ranking, .complaint select").change(function() { var name = $(this).data("name"); //get priority name if ($(".complaint select").val() === "Too_small" && $(this).val() == 1 && !$(this).data("increase_priority1")) { //rank is 1, and not yet added to priority list $("<option>", {text:name, val:name}).appendTo($increase_priority1); $(this).data("increase_priority1", true); //flag as a priority item } if ($(this).data("increase_priority1") && ($(this).val() != 1 || $(".complaint select").val() != "Too_small")) { //is in priority list, but now demoted $("option[value=" + name + "]", $increase_priority1).remove(); $(this).removeData("increase_priority1"); //no longer a priority item } // Similar If Statements to set & unset other elements go here }); HTML <div> <label>To Increase - 1rst Priority <select name="modify_increase_1rst[]" class="increase_priority1" multiple> </select></label> </div> <div> <span class="complaint"> <label>Shoulders</label> <select name=Shoulders> <option value="null">Select</option><option value="Too_small">Too Small</option><option value="Too_big">Too Big</option><option value="Too_expensive">Too expensive</option> </select> </span> <label>Ranking</label> <select name="importance_bother_shoulders" class="ranking shoulders" data-name="Shoulders"> <option value="Null">Select</option><option value="1">1</option><option value="2">2</option><option value="3">3</option><option value="4">4</option> <option value="5">5</option> </select> </div> <div> <span class="complaint"> <label>Waist</label> <select name=Waist> <option value="null">Select</option><option value="Too_small">Too Small</option><option value="Too_big">Too Big</option><option value="Too_expensive">Too expensive</option> </select> </span> <label>Ranking</label> <select name="importance_bother_waist" class="ranking waist" data-name="Waist"> <option value="Null">Select</option><option value="1">1</option><option value="2">2</option><option value="3">3</option><option value="4">4</option> <option value="5">5</option> </select> </div>

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  • What is wrong with my SQL syntax for an UPDATE with a JOIN?

    - by Phil H
    I have two tables, related by a common key. So TableA has key AID and value Name and TableB has keys AID, BID and values Name, Value: AID Name 74 Alpha AID BID Name Value 74 4 Beta Brilliance I would like to update the TableB Value here from Brilliance to Barmy, using just the Name fields. I thought I could do it via an UPDATE containing a JOIN, but Access (I know...) is complaining with 'Syntax error (missing operator) in query expression ' and then everything from 'Barmy' here: UPDATE tB SET tB.BValue='Barmy' FROM TableB tB INNER JOIN TableA tA ON tB.AID=tA.AID WHERE tB.Name='Beta' AND tA.Name='Alpha'; What is my heinous crime? Or is it just Access not conforming?

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  • How do I ensure data consistency in this concurrent situation?

    - by MalcomTucker
    The problem is this: I have multiple competing threads (100+) that need to access one database table Each thread will pass a String name - where that name exists in the table, the database should return the id for the row, where the name doesn't already exist, the name should be inserted and the id returned. There can only ever be one instance of name in the database - ie. name must be unique How do I ensure that thread one doesn't insert name1 at the same time as thread two also tries to insert name1? In other words, how do I guarantee the uniqueness of name in a concurrent environment? This also needs to be as efficient as possible - this has the potential to be a serious bottleneck. I am using MySQL and Java. Thanks

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  • Set primary key on hibernate generated sequence table

    - by bungrudi
    setup: hibernate 3.3, MySQL 5 I have an hibernate entity that have its PK generated using a sequence table. The annotation looks like this: @GenericGenerator(name = "SCENARIO_TABLE_GEN", strategy = "org.hibernate.id.enhanced.TableGenerator", parameters = { @Parameter(name = "initial_value", value = "5"), @Parameter(name = "force_table_use", value = "true"), @Parameter(name = "table_name", value = "SEQ_TABLE"), @Parameter(name = "value_column_name", value = "VALUE_COL"), @Parameter(name = "segment_column_name", value = "KEY_COL"), @Parameter(name = "segment_value", value = "SCENARIO") }) The problem is, that hibernate generated sequence table (SEQ_TABLE in my case, generated using hbm2ddl) does not have a primary keys. How do I tell hibernate that I want to have the primary key for the sequence table set on KEY_COL ?

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  • Getting Undefined index errors when trying to use $_POST

    - by Apoorv Agrawal
    I'm getting the following error messages: Notice: Undefined index: name in C:\xampp\htdocs\ApoorvProject\PostMethod.php on line 7 Notice: Undefined index: email in C:\xampp\htdocs\ApoorvProject\PostMethod.php on line 9 This is what line 7 and line 9 contains: echo $_POST["name"]; echo "<br>"; echo $_POST["email"]; This is the body of my HTML documnent: <form action="PostMethod.php" method="post"> Name: <input type="text" name="name" /> Email: <input type="text" name="email" /> <input type="submit" /> </form> PostMethod.php is the name of my PHP file.

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  • How do you escape parentheses in a Binding indexer

    - by Chris S
    I have the following XAML: <Grid x:Name="LayoutRoot" Background="White" DataContext="{Binding Source={StaticResource MyDataKey}}"> <TextBox Name="_myId" Text="{Binding MyDictionary[(Textbox.Name)]" /> </Grid> But it thinks the key in my dictionary is called "(Textbox.Name)", instead of "_myId". The format below works, where I have a property in my class called "_myId": <TextBox Name="_myId" Text="{Binding (Textbox.Name)" /> I've tried using ^ and \ to escape the brackets. Is this syntax supported? I'm trying to avoid duplication of the name in two attributes.

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  • How to disable the mediaplayer cookies

    - by Geetha
    Hi All, How to disable the mediaplayers cookies. Is there any parameter for that? Code: <object id="mediaPlayer" classid="clsid:22D6F312-B0F6-11D0-94AB-0080C74C7E95" codebase="http://activex.microsoft.com/activex/controls/mplayer/en/nsmp2inf.cab#Version=5,1,52,701" height="1" standby="Loading Microsoft Windows Media Player components..." type="application/x-oleobject" width="1"> <param name="fileName" value="" /> <param name="animationatStart" value="true" /> <param name="transparentatStart" value="true" /> <param name="autoStart" value="true" /> <param name="showControls" value="true" /> <param name="volume" value="100" /> <param name="loop" value="false" /> </object>

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  • In Drupal, can you control block display according to e.g. number of URL parts?

    - by james6848
    I'm having a little trouble controlling page-specific block display in Drupal... My URL's will be of this typical structure: http://www.mysite.co.uk/section-name/sub-page/sub-sub-page The 'section-name' will effectively be fixed, but there will be many sub-pages (far too many to explicitly reference). I need to somehow control block display as follows: One block will show on all pages where URL contains 'section-name/sub-page' but not on pages 'section-name/sub-page/sub-sub-page' Conversely, another block will show on all pages where URL contains 'section-name/sub-page/sub-sub-page' but not on pages 'section-name/sub-page' My only idea is to do a bit of PHP that looks for the string 'section-name' and then also counts URL parts (or even the number of slashes). Not sure how to implement that though :) Your help would be appreciated!

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  • Why my jquery is not working for a span tag

    - by Shantanu Gupta
    I am trying to display some message in span. but it is not working. <script type="text/javascript"> $(document).ready(function(){ /****************************First Name validation******************************/ $("#txtFirstName").bind("focusout",function(){ if($(this).val()=="" || $(this).val()=="First Name") { $(this).siblings("span[id*='error']").text("First Name Required"); $(this).val("First Name"); } }); $("#txtFirstName").bind("focusin",function(){ if($(this).val()=="First Name") { $(this).siblings("span[id*='error']").show("slow").text(""); $(this).val(""); } }); /********************End First Name validation*****************************/ }); Here is my html code for above code <td><input id="txtFirstName" type="text" value="First Name" runat="server"/><span class="error"></span></td>

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  • .htaccess Problem

    - by ocergynohtna
    I'm having trouble with redirecting urls using the .htaccess file. This is how my htaccess file looks like: Redirect 301 /file-name/example.php http://www.mysite.com/file-name/example-001.php Redirect 301 /section-name/example.php http://www.my-site.com/section-name/example-002.php RewriteEngine on RewriteCond %{HTTP_HOST} !^www.mysite.com$ [NC] RewriteRule ^(.*)$ http://www.mysite.com/$1 [L,R=301] RewriteCond %{REQUEST_FILENAME} !-f RewriteRule ^(.+)/(.*)$ hqtemplates/articles.php?file_name=$2 [L] php_value session.use_only_cookies 1 php_value session.use_trans_sid 0 Now the problem is that when I go to page: www.my-site.com/file-name/example.php instead of redirecting me to www.my-site.com/file-name/example-001.php it redirects me to www.my-site.com/file-name/example.php?file_name=example-001.php. For some reason it adds "?file_name=example-001.php" to the url. Anyone know's why this is happening and how to fix this?

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  • Remove specific string from multiple database rows in SQL

    - by Scott
    I have a column that contains page titles, which has the website name appended to the end of each. (e.g. Product Name | Company Name Inc.) I would like to remove the " | Company Name Inc." from multiple rows simultaneously. What SQl query commands (or query itself) would allow me to accomplish this? To re-illustrate, I want to convert multiple rows of 1 column from this: Product Name | Company Name Inc. To this: Product Name

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  • how to execute a .exe program by php script

    - by user347262
    hello I want to execute a .exe file on my Apache server using a php script. the procedure is as follow: 1- user comes, fills a html form 2- it goses to a php script 3- php script executes the name.exe file 4- php prints the output of the name.exe file on the page. I execute the name.exe normally from windows like this: run--> cmd--> D:\name [command] the name.exe needs to communicate with other files like libraries in the same directory. the complete comand in cmd at windows is like this: D:\name library.dll [input from user] then program executes and prints some results in cmd window. I actually want to run this program on my server form my clients. I dont know how, but I now there is a way to do this. another related questoin is that, is there any shell that i can install on Linux server and execute name.exe in it? thanks in advanced, John.

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  • error in python d not defined.

    - by dtechie
    Hi I am learning python and have this error . I can figure out where\what the error is in the code. File "<string>", line 1, in <module>. Name = "" Desc = "" Gender = "" Race = "" # Prompt user for user-defined information Name = input('What is your Name? ') Desc = input('Describe yourself: ') When i run the program it outputs What is your Name? (i input d ) this gives the error Traceback (most recent call last): File "/python/chargen.py", line 19, in <module> Name = input('What is your Name? ') File "<string>", line 1, in <module> NameError: name 'd' is not defined This is an example code from Python 3 for Absolute Beginners Thank you for your help :)

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  • how to select distinct rows for a column

    - by Satoru.Logic
    Hi, all. I have a table x that's like the one bellow: id | name | observed_value | 1 | a | 100 | 2 | b | 200 | 3 | b | 300 | 4 | a | 150 | 5 | c | 300 | I want to make a query so that in the result set I have exactly one record for one name: (1, a, 100) (2, b, 200) (5, c, 300) If there are multiple records corresponding to a name, say 'a' in the table above, I just pick up one of them. In my current implementation, I make a query like this: select x.* from x , (select distinct name, min(observed_value) as minimum_val from x group by name) x1 where x.name = x1.name and x.observed_value = x1.observed_value; But I think there may be some better way around, please tell me if you know, thanks in advance.

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  • Aligning textboxes via HTML

    - by Garry
    Here is my code: Classroom name: <input type="text" name="txtClassroomName" size="20"><br> School name: <input type="text" name="txtSchoolName" size="20"><br> School contact email address: <input type="text" name="txtSchoolEmail" size="20"><br> School address: <input type="text" name="txtSchoolAddress" size="20"><br> School telephone number: <input type="text" name="txtTelephoneNumber" size="20"><br> As you can probably guess, this code displays some text and then has some textboxes after this text. My question is this: I am wanting to align all the texboxes so that they are aligned. I have added spaces after the text, yet the textboxes just appear straight after the text, ignoring the spaces that I entered. What is the best, most effective way to do this? Maybe a table? thanks

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  • pass by const reference of class

    - by small_potato
    void foo(const ClassName &name) { ... } How can I access the method of class instance name? name.method() didn't work. then I tried: void foo(const ClassName &name) { ClassName temp = name; ... .... } I can use temp.method, but after foo was executed, the original name screwed up, any idea? BTW, the member variable of name didn't screwed up, but it was the member variable of subclass of class screwed up.

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  • PHP - javascript validation radio button

    - by user1806136
    i have a form with 3 sets of radio buttons. i want to set a simple javascript validation alert to appear when user clicks on submit when one of the fields is null. how can i do that using javascript ? my code so far is .. <?php session_start(); $Load=$_SESSION['login_user']; include('../connect.php'); if (isset($_POST['submit'])) { $v1 = intval($_POST['v1']); $v2 = intval($_POST['v2']); $v3 = intval($_POST['v3']); $total = $v1 + $v2 + $v3 ; mysql_query("INSERT into Form1 (P1,P2,P3,TOTAL) values('$v1','$v2','$v3','$total')") or die(mysql_error()); header("Location: mark.php"); } <center><form method="post" action="mark.php" > <tr> <th > School Evaluation <font size="4" > </font></th> <tr> <th > Criteria <font size="4" > </font></th> <th> 4<font size="4" > </font></th> <th> 3<font size="4" > </font></th> <th> 2<font size="4" > </font></th> <th> 1<font size="4" > </font></th> </tr> <tr> <th> Your attendance<font size="4" > </font></th> <td> <input type="radio" name ="v1" value = "4" onclick="updateTotal();"/></td> <td> <input type="radio" name ="v1" value = "3" onclick="updateTotal();" /></td> <td> <input type="radio" name ="v1" value = "2" onclick="updateTotal();" /></td> <td> <input type="radio" name ="v1" value = "1" onclick="updateTotal();" /></td> </tr> <tr> <th > Your grades <font size="4" > </font></th> <td> <input type="radio" name ="v2" value = "4" onclick="updateTotal();" /></td> <td> <input type="radio" name ="v2" value = "3" onclick="updateTotal();" /></td> <td> <input type="radio" name ="v2" value = "2" onclick="updateTotal();" /></td> <td> <input type="radio" name ="v2" value = "1" onclick="updateTotal();" /></td> </tr> <tr> <th >Your self-control <font size="4" > </font></th> <td> <input type="radio" name ="v3" value = "4" onclick="updateTotal();" /></td> <td> <input type="radio" name ="v3" value = "3" onclick="updateTotal();" /></td> <td> <input type="radio" name ="v3" value = "2" onclick="updateTotal();" /></td> <td> <input type="radio" name ="v3" value = "1" onclick="updateTotal();" /></td> </tr> </tr> </table> i have put <br> <td><input type="submit" name="submit" value="Submit" onClick="return validation(form);"> <input type="reset" name="clear" value="clear" style="width: 70px"></td> </form> i have try alot of codes but no alert appears!

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  • Strange SQL problem selecting multiple values for same column

    - by Nubber
    Hello there, Been at this for a few hours now and I can't make any sense of it. I've used this way of selecting multiple values for same column a few times, but there is something weird with this one. SELECT * FROM employee as s INNER JOIN works AS w1 ON w1.name = s.name INNER JOIN employee AS w2 ON w2.name = s.name INNER JOIN employee AS w3 ON w3.name = s.name WHERE w2.city = 'Washington' Basically what I want to do is find all companies which have people in all the cities. The company name is under 'works'. The problem is however that if I have the WHERE w2.city='Washington' it will make ALL the cities match Washington when it should only touch w2 and leave w3 alone so I could match it with another value. Anyone know why its doing this? Or know a better way to do it. Thank you very much in advance.

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  • replicating master tables mapping in transaction tables

    - by NoDisplay
    I have three master tables for location information Country {ID, Name} State {ID, Name, CountryID} City {ID, Name, StateID} Now I have one transcation table called Person which hold the person name and his location information. My Question is shall I have only CityID in the Person table like this: Person {ID, Name, CityID}' And have view of join query which give me detail like "Person{ID,Name,City,State,Country}" or Shall I replicate the mapping Person {ID, Name, CityID, StateID, CountryID} Please suggest which do you feel is to be selected and why? if there is any other option available, please suggest. Thanks in advance.

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  • The dynamic Type in C# Simplifies COM Member Access from Visual FoxPro

    - by Rick Strahl
    I’ve written quite a bit about Visual FoxPro interoperating with .NET in the past both for ASP.NET interacting with Visual FoxPro COM objects as well as Visual FoxPro calling into .NET code via COM Interop. COM Interop with Visual FoxPro has a number of problems but one of them at least got a lot easier with the introduction of dynamic type support in .NET. One of the biggest problems with COM interop has been that it’s been really difficult to pass dynamic objects from FoxPro to .NET and get them properly typed. The only way that any strong typing can occur in .NET for FoxPro components is via COM type library exports of Visual FoxPro components. Due to limitations in Visual FoxPro’s type library support as well as the dynamic nature of the Visual FoxPro language where few things are or can be described in the form of a COM type library, a lot of useful interaction between FoxPro and .NET required the use of messy Reflection code in .NET. Reflection is .NET’s base interface to runtime type discovery and dynamic execution of code without requiring strong typing. In FoxPro terms it’s similar to EVALUATE() functionality albeit with a much more complex API and corresponiding syntax. The Reflection APIs are fairly powerful, but they are rather awkward to use and require a lot of code. Even with the creation of wrapper utility classes for common EVAL() style Reflection functionality dynamically access COM objects passed to .NET often is pretty tedious and ugly. Let’s look at a simple example. In the following code I use some FoxPro code to dynamically create an object in code and then pass this object to .NET. An alternative to this might also be to create a new object on the fly by using SCATTER NAME on a database record. How the object is created is inconsequential, other than the fact that it’s not defined as a COM object – it’s a pure FoxPro object that is passed to .NET. Here’s the code: *** Create .NET COM InstanceloNet = CREATEOBJECT('DotNetCom.DotNetComPublisher') *** Create a Customer Object Instance (factory method) loCustomer = GetCustomer() loCustomer.Name = "Rick Strahl" loCustomer.Company = "West Wind Technologies" loCustomer.creditLimit = 9999999999.99 loCustomer.Address.StreetAddress = "32 Kaiea Place" loCustomer.Address.Phone = "808 579-8342" loCustomer.Address.Email = "[email protected]" *** Pass Fox Object and echo back values ? loNet.PassRecordObject(loObject) RETURN FUNCTION GetCustomer LOCAL loCustomer, loAddress loCustomer = CREATEOBJECT("EMPTY") ADDPROPERTY(loCustomer,"Name","") ADDPROPERTY(loCustomer,"Company","") ADDPROPERTY(loCUstomer,"CreditLimit",0.00) ADDPROPERTY(loCustomer,"Entered",DATETIME()) loAddress = CREATEOBJECT("Empty") ADDPROPERTY(loAddress,"StreetAddress","") ADDPROPERTY(loAddress,"Phone","") ADDPROPERTY(loAddress,"Email","") ADDPROPERTY(loCustomer,"Address",loAddress) RETURN loCustomer ENDFUNC Now prior to .NET 4.0 you’d have to access this object passed to .NET via Reflection and the method code to do this would looks something like this in the .NET component: public string PassRecordObject(object FoxObject) { // *** using raw Reflection string Company = (string) FoxObject.GetType().InvokeMember( "Company", BindingFlags.GetProperty,null, FoxObject,null); // using the easier ComUtils wrappers string Name = (string) ComUtils.GetProperty(FoxObject,"Name"); // Getting Address object – then getting child properties object Address = ComUtils.GetProperty(FoxObject,"Address");    string Street = (string) ComUtils.GetProperty(FoxObject,"StreetAddress"); // using ComUtils 'Ex' functions you can use . Syntax     string StreetAddress = (string) ComUtils.GetPropertyEx(FoxObject,"AddressStreetAddress"); return Name + Environment.NewLine + Company + Environment.NewLine + StreetAddress + Environment.NewLine + " FOX"; } Note that the FoxObject is passed in as type object which has no specific type. Since the object doesn’t exist in .NET as a type signature the object is passed without any specific type information as plain non-descript object. To retrieve a property the Reflection APIs like Type.InvokeMember or Type.GetProperty().GetValue() etc. need to be used. I made this code a little simpler by using the Reflection Wrappers I mentioned earlier but even with those ComUtils calls the code is pretty ugly requiring passing the objects for each call and casting each element. Using .NET 4.0 Dynamic Typing makes this Code a lot cleaner Enter .NET 4.0 and the dynamic type. Replacing the input parameter to the .NET method from type object to dynamic makes the code to access the FoxPro component inside of .NET much more natural: public string PassRecordObjectDynamic(dynamic FoxObject) { // *** using raw Reflection string Company = FoxObject.Company; // *** using the easier ComUtils class string Name = FoxObject.Name; // *** using ComUtils 'ex' functions to use . Syntax string Address = FoxObject.Address.StreetAddress; return Name + Environment.NewLine + Company + Environment.NewLine + Address + Environment.NewLine + " FOX"; } As you can see the parameter is of type dynamic which as the name implies performs Reflection lookups and evaluation on the fly so all the Reflection code in the last example goes away. The code can use regular object ‘.’ syntax to reference each of the members of the object. You can access properties and call methods this way using natural object language. Also note that all the type casts that were required in the Reflection code go away – dynamic types like var can infer the type to cast to based on the target assignment. As long as the type can be inferred by the compiler at compile time (ie. the left side of the expression is strongly typed) no explicit casts are required. Note that although you get to use plain object syntax in the code above you don’t get Intellisense in Visual Studio because the type is dynamic and thus has no hard type definition in .NET . The above example calls a .NET Component from VFP, but it also works the other way around. Another frequent scenario is an .NET code calling into a FoxPro COM object that returns a dynamic result. Assume you have a FoxPro COM object returns a FoxPro Cursor Record as an object: DEFINE CLASS FoxData AS SESSION OlePublic cAppStartPath = "" FUNCTION INIT THIS.cAppStartPath = ADDBS( JustPath(Application.ServerName) ) SET PATH TO ( THIS.cAppStartpath ) ENDFUNC FUNCTION GetRecord(lnPk) LOCAL loCustomer SELECT * FROM tt_Cust WHERE pk = lnPk ; INTO CURSOR TCustomer IF _TALLY < 1 RETURN NULL ENDIF SCATTER NAME loCustomer MEMO RETURN loCustomer ENDFUNC ENDDEFINE If you call this from a .NET application you can now retrieve this data via COM Interop and cast the result as dynamic to simplify the data access of the dynamic FoxPro type that was created on the fly: int pk = 0; int.TryParse(Request.QueryString["id"],out pk); // Create Fox COM Object with Com Callable Wrapper FoxData foxData = new FoxData(); dynamic foxRecord = foxData.GetRecord(pk); string company = foxRecord.Company; DateTime entered = foxRecord.Entered; This code looks simple and natural as it should be – heck you could write code like this in days long gone by in scripting languages like ASP classic for example. Compared to the Reflection code that previously was necessary to run similar code this is much easier to write, understand and maintain. For COM interop and Visual FoxPro operation dynamic type support in .NET 4.0 is a huge improvement and certainly makes it much easier to deal with FoxPro code that calls into .NET. Regardless of whether you’re using COM for calling Visual FoxPro objects from .NET (ASP.NET calling a COM component and getting a dynamic result returned) or whether FoxPro code is calling into a .NET COM component from a FoxPro desktop application. At one point or another FoxPro likely ends up passing complex dynamic data to .NET and for this the dynamic typing makes coding much cleaner and more readable without having to create custom Reflection wrappers. As a bonus the dynamic runtime that underlies the dynamic type is fairly efficient in terms of making Reflection calls especially if members are repeatedly accessed. © Rick Strahl, West Wind Technologies, 2005-2010Posted in COM  FoxPro  .NET  CSharp  

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  • An Xml Serializable PropertyBag Dictionary Class for .NET

    - by Rick Strahl
    I don't know about you but I frequently need property bags in my applications to store and possibly cache arbitrary data. Dictionary<T,V> works well for this although I always seem to be hunting for a more specific generic type that provides a string key based dictionary. There's string dictionary, but it only works with strings. There's Hashset<T> but it uses the actual values as keys. In most key value pair situations for me string is key value to work off. Dictionary<T,V> works well enough, but there are some issues with serialization of dictionaries in .NET. The .NET framework doesn't do well serializing IDictionary objects out of the box. The XmlSerializer doesn't support serialization of IDictionary via it's default serialization, and while the DataContractSerializer does support IDictionary serialization it produces some pretty atrocious XML. What doesn't work? First off Dictionary serialization with the Xml Serializer doesn't work so the following fails: [TestMethod] public void DictionaryXmlSerializerTest() { var bag = new Dictionary<string, object>(); bag.Add("key", "Value"); bag.Add("Key2", 100.10M); bag.Add("Key3", Guid.NewGuid()); bag.Add("Key4", DateTime.Now); bag.Add("Key5", true); bag.Add("Key7", new byte[3] { 42, 45, 66 }); TestContext.WriteLine(this.ToXml(bag)); } public string ToXml(object obj) { if (obj == null) return null; StringWriter sw = new StringWriter(); XmlSerializer ser = new XmlSerializer(obj.GetType()); ser.Serialize(sw, obj); return sw.ToString(); } The error you get with this is: System.NotSupportedException: The type System.Collections.Generic.Dictionary`2[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.Object, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]] is not supported because it implements IDictionary. Got it! BTW, the same is true with binary serialization. Running the same code above against the DataContractSerializer does work: [TestMethod] public void DictionaryDataContextSerializerTest() { var bag = new Dictionary<string, object>(); bag.Add("key", "Value"); bag.Add("Key2", 100.10M); bag.Add("Key3", Guid.NewGuid()); bag.Add("Key4", DateTime.Now); bag.Add("Key5", true); bag.Add("Key7", new byte[3] { 42, 45, 66 }); TestContext.WriteLine(this.ToXmlDcs(bag)); } public string ToXmlDcs(object value, bool throwExceptions = false) { var ser = new DataContractSerializer(value.GetType(), null, int.MaxValue, true, false, null); MemoryStream ms = new MemoryStream(); ser.WriteObject(ms, value); return Encoding.UTF8.GetString(ms.ToArray(), 0, (int)ms.Length); } This DOES work but produces some pretty heinous XML (formatted with line breaks and indentation here): <ArrayOfKeyValueOfstringanyType xmlns="http://schemas.microsoft.com/2003/10/Serialization/Arrays" xmlns:i="http://www.w3.org/2001/XMLSchema-instance"> <KeyValueOfstringanyType> <Key>key</Key> <Value i:type="a:string" xmlns:a="http://www.w3.org/2001/XMLSchema">Value</Value> </KeyValueOfstringanyType> <KeyValueOfstringanyType> <Key>Key2</Key> <Value i:type="a:decimal" xmlns:a="http://www.w3.org/2001/XMLSchema">100.10</Value> </KeyValueOfstringanyType> <KeyValueOfstringanyType> <Key>Key3</Key> <Value i:type="a:guid" xmlns:a="http://schemas.microsoft.com/2003/10/Serialization/">2cd46d2a-a636-4af4-979b-e834d39b6d37</Value> </KeyValueOfstringanyType> <KeyValueOfstringanyType> <Key>Key4</Key> <Value i:type="a:dateTime" xmlns:a="http://www.w3.org/2001/XMLSchema">2011-09-19T17:17:05.4406999-07:00</Value> </KeyValueOfstringanyType> <KeyValueOfstringanyType> <Key>Key5</Key> <Value i:type="a:boolean" xmlns:a="http://www.w3.org/2001/XMLSchema">true</Value> </KeyValueOfstringanyType> <KeyValueOfstringanyType> <Key>Key7</Key> <Value i:type="a:base64Binary" xmlns:a="http://www.w3.org/2001/XMLSchema">Ki1C</Value> </KeyValueOfstringanyType> </ArrayOfKeyValueOfstringanyType> Ouch! That seriously hurts the eye! :-) Worse though it's extremely verbose with all those repetitive namespace declarations. It's good to know that it works in a pinch, but for a human readable/editable solution or something lightweight to store in a database it's not quite ideal. Why should I care? As a little background, in one of my applications I have a need for a flexible property bag that is used on a free form database field on an otherwise static entity. Basically what I have is a standard database record to which arbitrary properties can be added in an XML based string field. I intend to expose those arbitrary properties as a collection from field data stored in XML. The concept is pretty simple: When loading write the data to the collection, when the data is saved serialize the data into an XML string and store it into the database. When reading the data pick up the XML and if the collection on the entity is accessed automatically deserialize the XML into the Dictionary. (I'll talk more about this in another post). While the DataContext Serializer would work, it's verbosity is problematic both for size of the generated XML strings and the fact that users can manually edit this XML based property data in an advanced mode. A clean(er) layout certainly would be preferable and more user friendly. Custom XMLSerialization with a PropertyBag Class So… after a bunch of experimentation with different serialization formats I decided to create a custom PropertyBag class that provides for a serializable Dictionary. It's basically a custom Dictionary<TType,TValue> implementation with the keys always set as string keys. The result are PropertyBag<TValue> and PropertyBag (which defaults to the object type for values). The PropertyBag<TType> and PropertyBag classes provide these features: Subclassed from Dictionary<T,V> Implements IXmlSerializable with a cleanish XML format ToXml() and FromXml() methods to export and import to and from XML strings Static CreateFromXml() method to create an instance It's simple enough as it's merely a Dictionary<string,object> subclass but that supports serialization to a - what I think at least - cleaner XML format. The class is super simple to use: [TestMethod] public void PropertyBagTwoWayObjectSerializationTest() { var bag = new PropertyBag(); bag.Add("key", "Value"); bag.Add("Key2", 100.10M); bag.Add("Key3", Guid.NewGuid()); bag.Add("Key4", DateTime.Now); bag.Add("Key5", true); bag.Add("Key7", new byte[3] { 42,45,66 } ); bag.Add("Key8", null); bag.Add("Key9", new ComplexObject() { Name = "Rick", Entered = DateTime.Now, Count = 10 }); string xml = bag.ToXml(); TestContext.WriteLine(bag.ToXml()); bag.Clear(); bag.FromXml(xml); Assert.IsTrue(bag["key"] as string == "Value"); Assert.IsInstanceOfType( bag["Key3"], typeof(Guid)); Assert.IsNull(bag["Key8"]); //Assert.IsNull(bag["Key10"]); Assert.IsInstanceOfType(bag["Key9"], typeof(ComplexObject)); } This uses the PropertyBag class which uses a PropertyBag<string,object> - which means it returns untyped values of type object. I suspect for me this will be the most common scenario as I'd want to store arbitrary values in the PropertyBag rather than one specific type. The same code with a strongly typed PropertyBag<decimal> looks like this: [TestMethod] public void PropertyBagTwoWayValueTypeSerializationTest() { var bag = new PropertyBag<decimal>(); bag.Add("key", 10M); bag.Add("Key1", 100.10M); bag.Add("Key2", 200.10M); bag.Add("Key3", 300.10M); string xml = bag.ToXml(); TestContext.WriteLine(bag.ToXml()); bag.Clear(); bag.FromXml(xml); Assert.IsTrue(bag.Get("Key1") == 100.10M); Assert.IsTrue(bag.Get("Key3") == 300.10M); } and produces typed results of type decimal. The types can be either value or reference types the combination of which actually proved to be a little more tricky than anticipated due to null and specific string value checks required - getting the generic typing right required use of default(T) and Convert.ChangeType() to trick the compiler into playing nice. Of course the whole raison d'etre for this class is the XML serialization. You can see in the code above that we're doing a .ToXml() and .FromXml() to serialize to and from string. The XML produced for the first example looks like this: <?xml version="1.0" encoding="utf-8"?> <properties> <item> <key>key</key> <value>Value</value> </item> <item> <key>Key2</key> <value type="decimal">100.10</value> </item> <item> <key>Key3</key> <value type="___System.Guid"> <guid>f7a92032-0c6d-4e9d-9950-b15ff7cd207d</guid> </value> </item> <item> <key>Key4</key> <value type="datetime">2011-09-26T17:45:58.5789578-10:00</value> </item> <item> <key>Key5</key> <value type="boolean">true</value> </item> <item> <key>Key7</key> <value type="base64Binary">Ki1C</value> </item> <item> <key>Key8</key> <value type="nil" /> </item> <item> <key>Key9</key> <value type="___Westwind.Tools.Tests.PropertyBagTest+ComplexObject"> <ComplexObject> <Name>Rick</Name> <Entered>2011-09-26T17:45:58.5789578-10:00</Entered> <Count>10</Count> </ComplexObject> </value> </item> </properties>   The format is a bit cleaner than the DataContractSerializer. Each item is serialized into <key> <value> pairs. If the value is a string no type information is written. Since string tends to be the most common type this saves space and serialization processing. All other types are attributed. Simple types are mapped to XML types so things like decimal, datetime, boolean and base64Binary are encoded using their Xml type values. All other types are embedded with a hokey format that describes the .NET type preceded by a three underscores and then are encoded using the XmlSerializer. You can see this best above in the ComplexObject encoding. For custom types this isn't pretty either, but it's more concise than the DCS and it works as long as you're serializing back and forth between .NET clients at least. The XML generated from the second example that uses PropertyBag<decimal> looks like this: <?xml version="1.0" encoding="utf-8"?> <properties> <item> <key>key</key> <value type="decimal">10</value> </item> <item> <key>Key1</key> <value type="decimal">100.10</value> </item> <item> <key>Key2</key> <value type="decimal">200.10</value> </item> <item> <key>Key3</key> <value type="decimal">300.10</value> </item> </properties>   How does it work As I mentioned there's nothing fancy about this solution - it's little more than a subclass of Dictionary<T,V> that implements custom Xml Serialization and a couple of helper methods that facilitate getting the XML in and out of the class more easily. But it's proven very handy for a number of projects for me where dynamic data storage is required. Here's the code: /// <summary> /// Creates a serializable string/object dictionary that is XML serializable /// Encodes keys as element names and values as simple values with a type /// attribute that contains an XML type name. Complex names encode the type /// name with type='___namespace.classname' format followed by a standard xml /// serialized format. The latter serialization can be slow so it's not recommended /// to pass complex types if performance is critical. /// </summary> [XmlRoot("properties")] public class PropertyBag : PropertyBag<object> { /// <summary> /// Creates an instance of a propertybag from an Xml string /// </summary> /// <param name="xml">Serialize</param> /// <returns></returns> public static PropertyBag CreateFromXml(string xml) { var bag = new PropertyBag(); bag.FromXml(xml); return bag; } } /// <summary> /// Creates a serializable string for generic types that is XML serializable. /// /// Encodes keys as element names and values as simple values with a type /// attribute that contains an XML type name. Complex names encode the type /// name with type='___namespace.classname' format followed by a standard xml /// serialized format. The latter serialization can be slow so it's not recommended /// to pass complex types if performance is critical. /// </summary> /// <typeparam name="TValue">Must be a reference type. For value types use type object</typeparam> [XmlRoot("properties")] public class PropertyBag<TValue> : Dictionary<string, TValue>, IXmlSerializable { /// <summary> /// Not implemented - this means no schema information is passed /// so this won't work with ASMX/WCF services. /// </summary> /// <returns></returns> public System.Xml.Schema.XmlSchema GetSchema() { return null; } /// <summary> /// Serializes the dictionary to XML. Keys are /// serialized to element names and values as /// element values. An xml type attribute is embedded /// for each serialized element - a .NET type /// element is embedded for each complex type and /// prefixed with three underscores. /// </summary> /// <param name="writer"></param> public void WriteXml(System.Xml.XmlWriter writer) { foreach (string key in this.Keys) { TValue value = this[key]; Type type = null; if (value != null) type = value.GetType(); writer.WriteStartElement("item"); writer.WriteStartElement("key"); writer.WriteString(key as string); writer.WriteEndElement(); writer.WriteStartElement("value"); string xmlType = XmlUtils.MapTypeToXmlType(type); bool isCustom = false; // Type information attribute if not string if (value == null) { writer.WriteAttributeString("type", "nil"); } else if (!string.IsNullOrEmpty(xmlType)) { if (xmlType != "string") { writer.WriteStartAttribute("type"); writer.WriteString(xmlType); writer.WriteEndAttribute(); } } else { isCustom = true; xmlType = "___" + value.GetType().FullName; writer.WriteStartAttribute("type"); writer.WriteString(xmlType); writer.WriteEndAttribute(); } // Actual deserialization if (!isCustom) { if (value != null) writer.WriteValue(value); } else { XmlSerializer ser = new XmlSerializer(value.GetType()); ser.Serialize(writer, value); } writer.WriteEndElement(); // value writer.WriteEndElement(); // item } } /// <summary> /// Reads the custom serialized format /// </summary> /// <param name="reader"></param> public void ReadXml(System.Xml.XmlReader reader) { this.Clear(); while (reader.Read()) { if (reader.NodeType == XmlNodeType.Element && reader.Name == "key") { string xmlType = null; string name = reader.ReadElementContentAsString(); // item element reader.ReadToNextSibling("value"); if (reader.MoveToNextAttribute()) xmlType = reader.Value; reader.MoveToContent(); TValue value; if (xmlType == "nil") value = default(TValue); // null else if (string.IsNullOrEmpty(xmlType)) { // value is a string or object and we can assign TValue to value string strval = reader.ReadElementContentAsString(); value = (TValue) Convert.ChangeType(strval, typeof(TValue)); } else if (xmlType.StartsWith("___")) { while (reader.Read() && reader.NodeType != XmlNodeType.Element) { } Type type = ReflectionUtils.GetTypeFromName(xmlType.Substring(3)); //value = reader.ReadElementContentAs(type,null); XmlSerializer ser = new XmlSerializer(type); value = (TValue)ser.Deserialize(reader); } else value = (TValue)reader.ReadElementContentAs(XmlUtils.MapXmlTypeToType(xmlType), null); this.Add(name, value); } } } /// <summary> /// Serializes this dictionary to an XML string /// </summary> /// <returns>XML String or Null if it fails</returns> public string ToXml() { string xml = null; SerializationUtils.SerializeObject(this, out xml); return xml; } /// <summary> /// Deserializes from an XML string /// </summary> /// <param name="xml"></param> /// <returns>true or false</returns> public bool FromXml(string xml) { this.Clear(); // if xml string is empty we return an empty dictionary if (string.IsNullOrEmpty(xml)) return true; var result = SerializationUtils.DeSerializeObject(xml, this.GetType()) as PropertyBag<TValue>; if (result != null) { foreach (var item in result) { this.Add(item.Key, item.Value); } } else // null is a failure return false; return true; } /// <summary> /// Creates an instance of a propertybag from an Xml string /// </summary> /// <param name="xml"></param> /// <returns></returns> public static PropertyBag<TValue> CreateFromXml(string xml) { var bag = new PropertyBag<TValue>(); bag.FromXml(xml); return bag; } } } The code uses a couple of small helper classes SerializationUtils and XmlUtils for mapping Xml types to and from .NET, both of which are from the WestWind,Utilities project (which is the same project where PropertyBag lives) from the West Wind Web Toolkit. The code implements ReadXml and WriteXml for the IXmlSerializable implementation using old school XmlReaders and XmlWriters (because it's pretty simple stuff - no need for XLinq here). Then there are two helper methods .ToXml() and .FromXml() that basically allow your code to easily convert between XML and a PropertyBag object. In my code that's what I use to actually to persist to and from the entity XML property during .Load() and .Save() operations. It's sweet to be able to have a string key dictionary and then be able to turn around with 1 line of code to persist the whole thing to XML and back. Hopefully some of you will find this class as useful as I've found it. It's a simple solution to a common requirement in my applications and I've used the hell out of it in the  short time since I created it. Resources You can find the complete code for the two classes plus the helpers in the Subversion repository for Westwind.Utilities. You can grab the source files from there or download the whole project. You can also grab the full Westwind.Utilities assembly from NuGet and add it to your project if that's easier for you. PropertyBag Source Code SerializationUtils and XmlUtils Westwind.Utilities Assembly on NuGet (add from Visual Studio) © Rick Strahl, West Wind Technologies, 2005-2011Posted in .NET  CSharp   Tweet (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • jQuery Templates with ASP.NET MVC

    - by hajan
    In my three previous blogs, I’ve shown how to use Templates in your ASPX website. Introduction to jQuery TemplatesjQuery Templates - tmpl(), template() and tmplItem()jQuery Templates - {Supported Tags}Now, I will show one real-world example which you may use it in your daily work of developing applications with ASP.NET MVC and jQuery. In the following example I will use Pubs database so that I will retrieve values from the authors table. To access the data, I’m using Entity Framework. Let’s pass throughout each step of the scenario: 1. Create new ASP.NET MVC Web application 2. Add new View inside Home folder but do not select a master page, and add Controller for your View 3. BODY code in the HTML <body>     <div>         <h1>Pubs Authors</h1>         <div id="authorsList"></div>     </div> </body> As you can see  in the body we have only one H1 tag and a div with id authorsList where we will append the data from database.   4. Now, I’ve created Pubs model which is connected to the Pub database and I’ve selected only the authors table in my EDMX model. You can use your own database. 5. Next, lets create one method of JsonResult type which will get the data from database and serialize it into JSON string. public JsonResult GetAuthors() {     pubsEntities pubs = new pubsEntities();     var authors = pubs.authors.ToList();     return Json(authors, JsonRequestBehavior.AllowGet); } So, I’m creating object instance of pubsEntities and get all authors in authors list. Then returning the authors list by serializing it to JSON using Json method. The JsonRequestBehaviour.AllowGet parameter is used to make the GET requests from the client become allowed. By default in ASP.NET MVC 2 the GET is not allowed because of security issue with JSON hijacking.   6. Next, lets create jQuery AJAX function which will call the GetAuthors method. We will use $.getJSON jQuery method. <script language="javascript" type="text/javascript">     $(function () {         $.getJSON("GetAuthors", "", function (data) {             $("#authorsTemplate").tmpl(data).appendTo("#authorsList");         });     }); </script>   Once the web page is downloaded, the method will be called. The first parameter of $.getJSON() is url string in our case the method name. The second parameter (which in the example is empty string) is the key value pairs that will be send to the server, and the third function is the callback function or the result which is going to be returned from the server. Inside the callback function we have code that renders data with template which has id #authorsTemplate and appends it to element which has #authorsList ID.   7. The jQuery Template <script id="authorsTemplate" type="text/html">     <div id="author">         ${au_lname} ${au_fname}         <div id="address">${address}, ${city}</div>         <div id="contractType">                     {{if contract}}             <font color="green">Has contract with the publishing house</font>         {{else}}             <font color="red">Without contract</font>         {{/if}}         <br />         <em> ${printMessage(state)} </em>         <br />                     </div>     </div> </script> As you can see, I have tags containing fields (au_lname, au_fname… etc.) that corresponds to the table in the EDMX model which is the same as in the database. One more thing to note here is that I have printMessage(state) function which is called inside ${ expression/function/field } tag. The printMessage function <script language="javascript" type="text/javascript">     function printMessage(s) {         if (s=="CA") return "The author is from California";         else return "The author is not from California";     } </script> So, if state is “CA” print “The author is from California” else “The author is not from California”   HERE IS THE COMPLETE ASPX CODE <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server">     <title>Database Example :: jQuery Templates</title>     <style type="text/css">         body           {             font-family:Verdana,Arial,Courier New, Sans-Serif;             color:Black;             padding:2px, 2px, 2px, 2px;             background-color:#FF9640;         }         #author         {             display:block;             float:left;             text-decoration:none;             border:1px solid black;             background-color:White;             padding:20px 20px 20px 20px;             margin-top:2px;             margin-right:2px;             font-family:Verdana;             font-size:12px;             width:200px;             height:70px;}         #address           {             font-style:italic;             color:Blue;             font-size:12px;             font-family:Verdana;         }         .author_hover {background-color:Yellow;}     </style>     <script src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.4.4.min.js" type="text/javascript"></script>     <script src="http://ajax.aspnetcdn.com/ajax/jquery.templates/beta1/jquery.tmpl.js" type="text/javascript"></script>     <script language="javascript" type="text/javascript">         function printMessage(s) {             if (s=="CA") return "The author is from California";             else return "The author is not from California";         }     </script>     <script id="authorsTemplate" type="text/html">         <div id="author">             ${au_lname} ${au_fname}             <div id="address">${address}, ${city}</div>             <div id="contractType">                         {{if contract}}                 <font color="green">Has contract with the publishing house</font>             {{else}}                 <font color="red">Without contract</font>             {{/if}}             <br />             <em> ${printMessage(state)} </em>             <br />                         </div>         </div>     </script>     <script language="javascript" type="text/javascript">         $(function () {             $.getJSON("GetAuthors", "", function (data) {                 $("#authorsTemplate").tmpl(data).appendTo("#authorsList");             });         });     </script> </head>     <body>     <div id="title">Pubs Authors</div>     <div id="authorsList"></div> </body> </html> So, in the complete example you also have the CSS style I’m using to stylize the output of my page. Here is print screen of the end result displayed on the web page: You can download the complete source code including examples shown in my previous blog posts about jQuery templates and PPT presentation from my last session I had in the local .NET UG meeting in the following DOWNLOAD LINK. Do let me know your feedback. Regards, Hajan

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  • Generate Strongly Typed Observable Events for the Reactive Extensions for .NET (Rx)

    - by Bobby Diaz
    I must have tried reading through the various explanations and introductions to the new Reactive Extensions for .NET before the concepts finally started sinking in.  The article that gave me the ah-ha moment was over on SilverlightShow.net and titled Using Reactive Extensions in Silverlight.  The author did a good job comparing the "normal" way of handling events vs. the new "reactive" methods. Admittedly, I still have more to learn about the Rx Framework, but I wanted to put together a sample project so I could start playing with the new Observable and IObservable<T> constructs.  I decided to throw together a whiteboard application in Silverlight based on the Drawing with Rx example on the aforementioned article.  At the very least, I figured I would learn a thing or two about a new technology, but my real goal is to create a fun application that I can share with the kids since they love drawing and coloring so much! Here is the code sample that I borrowed from the article: var mouseMoveEvent = Observable.FromEvent<MouseEventArgs>(this, "MouseMove"); var mouseLeftButtonDown = Observable.FromEvent<MouseButtonEventArgs>(this, "MouseLeftButtonDown"); var mouseLeftButtonUp = Observable.FromEvent<MouseButtonEventArgs>(this, "MouseLeftButtonUp");       var draggingEvents = from pos in mouseMoveEvent                              .SkipUntil(mouseLeftButtonDown)                              .TakeUntil(mouseLeftButtonUp)                              .Let(mm => mm.Zip(mm.Skip(1), (prev, cur) =>                                  new                                  {                                      X2 = cur.EventArgs.GetPosition(this).X,                                      X1 = prev.EventArgs.GetPosition(this).X,                                      Y2 = cur.EventArgs.GetPosition(this).Y,                                      Y1 = prev.EventArgs.GetPosition(this).Y                                  })).Repeat()                          select pos;       draggingEvents.Subscribe(p =>     {         Line line = new Line();         line.Stroke = new SolidColorBrush(Colors.Black);         line.StrokeEndLineCap = PenLineCap.Round;         line.StrokeLineJoin = PenLineJoin.Round;         line.StrokeThickness = 5;         line.X1 = p.X1;         line.Y1 = p.Y1;         line.X2 = p.X2;         line.Y2 = p.Y2;         this.LayoutRoot.Children.Add(line);     }); One thing that was nagging at the back of my mind was having to deal with the event names as strings, as well as the verbose syntax for the Observable.FromEvent<TEventArgs>() method.  I came up with a couple of static/helper classes to resolve both issues and also created a T4 template to auto-generate these helpers for any .NET type.  Take the following code from the above example: var mouseMoveEvent = Observable.FromEvent<MouseEventArgs>(this, "MouseMove"); var mouseLeftButtonDown = Observable.FromEvent<MouseButtonEventArgs>(this, "MouseLeftButtonDown"); var mouseLeftButtonUp = Observable.FromEvent<MouseButtonEventArgs>(this, "MouseLeftButtonUp"); Turns into this with the new static Events class: var mouseMoveEvent = Events.Mouse.Move.On(this); var mouseLeftButtonDown = Events.Mouse.LeftButtonDown.On(this); var mouseLeftButtonUp = Events.Mouse.LeftButtonUp.On(this); Or better yet, just remove the variable declarations altogether:     var draggingEvents = from pos in Events.Mouse.Move.On(this)                              .SkipUntil(Events.Mouse.LeftButtonDown.On(this))                              .TakeUntil(Events.Mouse.LeftButtonUp.On(this))                              .Let(mm => mm.Zip(mm.Skip(1), (prev, cur) =>                                  new                                  {                                      X2 = cur.EventArgs.GetPosition(this).X,                                      X1 = prev.EventArgs.GetPosition(this).X,                                      Y2 = cur.EventArgs.GetPosition(this).Y,                                      Y1 = prev.EventArgs.GetPosition(this).Y                                  })).Repeat()                          select pos; The Move, LeftButtonDown and LeftButtonUp members of the Events.Mouse class are readonly instances of the ObservableEvent<TTarget, TEventArgs> class that provide type-safe access to the events via the On() method.  Here is the code for the class: using System; using System.Collections.Generic; using System.Linq;   namespace System.Linq {     /// <summary>     /// Represents an event that can be managed via the <see cref="Observable"/> API.     /// </summary>     /// <typeparam name="TTarget">The type of the target.</typeparam>     /// <typeparam name="TEventArgs">The type of the event args.</typeparam>     public class ObservableEvent<TTarget, TEventArgs> where TEventArgs : EventArgs     {         /// <summary>         /// Initializes a new instance of the <see cref="ObservableEvent"/> class.         /// </summary>         /// <param name="eventName">Name of the event.</param>         protected ObservableEvent(String eventName)         {             EventName = eventName;         }           /// <summary>         /// Registers the specified event name.         /// </summary>         /// <param name="eventName">Name of the event.</param>         /// <returns></returns>         public static ObservableEvent<TTarget, TEventArgs> Register(String eventName)         {             return new ObservableEvent<TTarget, TEventArgs>(eventName);         }           /// <summary>         /// Creates an enumerable sequence of event values for the specified target.         /// </summary>         /// <param name="target">The target.</param>         /// <returns></returns>         public IObservable<IEvent<TEventArgs>> On(TTarget target)         {             return Observable.FromEvent<TEventArgs>(target, EventName);         }           /// <summary>         /// Gets or sets the name of the event.         /// </summary>         /// <value>The name of the event.</value>         public string EventName { get; private set; }     } } And this is how it's used:     /// <summary>     /// Categorizes <see cref="ObservableEvents"/> by class and/or functionality.     /// </summary>     public static partial class Events     {         /// <summary>         /// Implements a set of predefined <see cref="ObservableEvent"/>s         /// for the <see cref="System.Windows.System.Windows.UIElement"/> class         /// that represent mouse related events.         /// </summary>         public static partial class Mouse         {             /// <summary>Represents the MouseMove event.</summary>             public static readonly ObservableEvent<UIElement, MouseEventArgs> Move =                 ObservableEvent<UIElement, MouseEventArgs>.Register("MouseMove");               // additional members omitted...         }     } The source code contains a static Events class with prefedined members for various categories (Key, Mouse, etc.).  There is also an Events.tt template that you can customize to generate additional event categories for any .NET type.  All you should have to do is add the name of your class to the types collection near the top of the template:     types = new Dictionary<String, Type>()     {         //{ "Microsoft.Maps.MapControl.Map, Microsoft.Maps.MapControl", null }         { "System.Windows.FrameworkElement, System.Windows", null },         { "Whiteboard.MainPage, Whiteboard", null }     }; The template is also a bit rough at this point, but at least it generates code that *should* compile.  Please let me know if you run into any issues with it.  Some people have reported errors when trying to use T4 templates within a Silverlight project, but I was able to get it to work with a little black magic...  You can download the source code for this project or play around with the live demo.  Just be warned that it is at a very early stage so don't expect to find much today.  I plan on adding alot more options like pen colors and sizes, saving, printing, etc. as time permits.  HINT: hold down the ESC key to erase! Enjoy! Additional Resources Using Reactive Extensions in Silverlight DevLabs: Reactive Extensions for .NET (Rx) Rx Framework Part III - LINQ to Events - Generating GetEventName() Wrapper Methods using T4

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  • Small adventure game

    - by Nick Rosencrantz
    I'm making a small adventure game where the player can walk through Dungeons and meet scary characters: The whole thing is 20 java classes and I'm making this a standalone frame while it could very well be an applet I don't want to make another applet since I might want to recode this in C/C++ if the game or game engine turns out a success. The engine is the most interesting part of the game, it controls players and computer-controlled characters such as Zombies, Reptile Warriors, Trolls, Necromancers, and other Persons. These persons can sleep or walk around in the game and also pick up and move things. I didn't add many things so I suppose that is the next thing to do is to add things that can get used now that I already added many different types of walking persons. What do you think I should add and do with things in the game? The things I have so far is: package adventure; /** * The data type for things. Subclasses will be create that takes part of the story */ public class Thing { /** * The name of the Thing. */ public String name; /** * @param name The name of the Thing. */ Thing( String name ) { this.name = name; } } public class Scroll extends Thing { Scroll (String name) { super(name); } } class Key extends Thing { Key (String name) { super(name); } } The key is the way to win the game if you figure our that you should give it to a certain person and the scroll can protect you from necromancers and trolls. If I make this game more Dungeons and Dragons-inspired, do you think will be any good? Any other ideas that you think I could use here? The Threadwhich steps time forward and wakes up persons is called simulation. Do you think I could do something more advanced with this class? package adventure; class Simulation extends Thread { private PriorityQueue Eventqueue; Simulation() { Eventqueue = new PriorityQueue(); start(); } public void wakeMeAfter(Wakeable SleepingObject, double time) { Eventqueue.enqueue(SleepingObject, System.currentTimeMillis()+time); } public void run() { while(true) { try { sleep(5); //Sov i en halv sekund if (Eventqueue.getFirstTime() <= System.currentTimeMillis()) { ((Wakeable)Eventqueue.getFirst()).wakeup(); Eventqueue.dequeue(); } } catch (InterruptedException e ) { } } } } And here is the class that makes up the actual world: package adventure; import java.awt.*; import java.net.URL; /** * Subklass to World that builds up the Dungeon World. */ public class DungeonWorld extends World { /** * * @param a Reference to adventure game. * */ public DungeonWorld(Adventure a) { super ( a ); // Create all places createPlace( "Himlen" ); createPlace( "Stairs3" ); createPlace( "IPLab" ); createPlace( "Dungeon3" ); createPlace( "Stairs5" ); createPlace( "C2M2" ); createPlace( "SANS" ); createPlace( "Macsal" ); createPlace( "Stairs4" ); createPlace( "Dungeon2" ); createPlace( "Datorsalen" ); createPlace( "Dungeon");//, "Ljushallen.gif" ); createPlace( "Cola-automaten", "ColaAutomat.gif" ); createPlace( "Stairs2" ); createPlace( "Fable1" ); createPlace( "Dungeon1" ); createPlace( "Kulverten" ); // Create all connections between places connect( "Stairs3", "Stairs5", "Down", "Up" ); connect( "Dungeon3", "SANS", "Down", "Up" ); connect( "Dungeon3", "IPLab", "West", "East" ); connect( "IPLab", "Stairs3", "West", "East" ); connect( "Stairs5", "Stairs4", "Down", "Up" ); connect( "Macsal", "Stairs5", "South", "Norr" ); connect( "C2M2", "Stairs5", "West", "East" ); connect( "SANS", "C2M2", "West", "East" ); connect( "Stairs4", "Dungeon", "Down", "Up" ); connect( "Datorsalen", "Stairs4", "South", "Noth" ); connect( "Dungeon2", "Stairs4", "West", "East" ); connect( "Dungeon", "Stairs2", "Down", "Up" ); connect( "Dungeon", "Cola-automaten", "South", "North" ); connect( "Stairs2", "Kulverten", "Down", "Up" ); connect( "Stairs2", "Fable1", "East", "West" ); connect( "Fable1", "Dungeon1", "South", "North" ); // Add things // --- Add new things here --- getPlace("Cola-automaten").addThing(new CocaCola("Ljummen cola")); getPlace("Cola-automaten").addThing(new CocaCola("Avslagen Cola")); getPlace("Cola-automaten").addThing(new CocaCola("Iskall Cola")); getPlace("Cola-automaten").addThing(new CocaCola("Cola Light")); getPlace("Cola-automaten").addThing(new CocaCola("Cuba Cola")); getPlace("Stairs4").addThing(new Scroll("Scroll")); getPlace("Dungeon3").addThing(new Key("Key")); Simulation sim = new Simulation(); // Load images to be used as appearance-parameter for persons Image studAppearance = owner.loadPicture( "Person.gif" ); Image asseAppearance = owner.loadPicture( "Asse.gif" ); Image trollAppearance = owner.loadPicture( "Loke.gif" ); Image necromancerAppearance = owner.loadPicture( "Necromancer.gif" ); Image skeletonAppearance = owner.loadPicture( "Reptilewarrior.gif" ); Image reptileAppearance = owner.loadPicture( "Skeleton.gif" ); Image zombieAppearance = owner.loadPicture( "Zombie.gif" ); // --- Add new persons here --- new WalkingPerson(sim, this, "Peter", studAppearance); new WalkingPerson(sim, this, "Zombie", zombieAppearance ); new WalkingPerson(sim, this, "Zombie", zombieAppearance ); new WalkingPerson(sim, this, "Skeleton", skeletonAppearance ); new WalkingPerson(sim, this, "John", studAppearance ); new WalkingPerson(sim, this, "Skeleton", skeletonAppearance ); new WalkingPerson(sim, this, "Skeleton", skeletonAppearance ); new WalkingPerson(sim, this, "Skeleton", skeletonAppearance ); new WalkingPerson(sim, this, "Sean", studAppearance ); new WalkingPerson(sim, this, "Reptile", reptileAppearance ); new LabAssistant(sim, this, "Kate", asseAppearance); new LabAssistant(sim, this, "Jenna", asseAppearance); new Troll(sim, this, "Troll", trollAppearance); new Necromancer(sim, this, "Necromancer", necromancerAppearance); } /** * * The place where persons are placed by default * *@return The default place. * */ public Place defaultPlace() { return getPlace( "Datorsalen" ); } private void connect( String p1, String p2, String door1, String door2) { Place place1 = getPlace( p1 ); Place place2 = getPlace( p2 ); place1.addExit( door1, place2 ); place2.addExit( door2, place1 ); } } Thanks

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