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  • LaTeX Double Spacing

    - by reprogrammer
    I am using the acm LaTeX template and I have trouble making my paper double spaced. My LaTeX document looks like the following: \documentclass{acm_proc_article-sp} \usepackage{setspace} \doublespacing \begin{document} ... \end{document} When I compile the above document using pdflatex, I get the following error message on the line that I use the command \doublespacing: Missing number, treated as zero \doublespacing

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  • QPlainTextEdit segmentation fault

    - by Alexander
    Hi, All! I have some Qt application with QPlainTextEdit in Tab widget. When try to make a pointer on it QPlainTextEdit *w = (QPlainTextEdit*)ui->tabWidget->widget(0) and call a document() method w->document() I get a segfault. But if i call document directly, e.g. ui-mainEdit-document(), then everything works fine. Can anybody explain me why it happens?

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  • What (tf) are the secrets behind PDF memory allocation (CGPDFDocumentRef)

    - by Kai
    For a PDF reader I want to prepare a document by taking 'screenshots' of each page and save them to disc. First approach is CGPDFDocumentRef document = CGPDFDocumentCreateWithURL((CFURLRef) someURL); for (int i = 1; i<=pageCount; i++) { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc]init]; CGPDFPageRef page = CGPDFDocumentGetPage(document, i); ...//getting + manipulating graphics context etc. ... CGContextDrawPDFPage(context, page); ... UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext(); ...//saving the image to disc [pool drain]; } CGPDFDocumentRelease(document); This results in a lot of memory which seems not to be released after the first run of the loop (preparing the 1st document), but no more unreleased memory in additional runs: MEMORY BEFORE: 6 MB MEMORY DURING 1ST DOC: 40 MB MEMORY AFTER 1ST DOC: 25 MB MEMORY DURING 2ND DOC: 40 MB MEMORY AFTER 2ND DOC: 25 MB .... Changing the code to for (int i = 1; i<=pageCount; i++) { CGPDFDocumentRef document = CGPDFDocumentCreateWithURL((CFURLRef) someURL); NSAutoreleasePool *pool = [[NSAutoreleasePool alloc]init]; CGPDFPageRef page = CGPDFDocumentGetPage(document, i); ...//getting + manipulating graphics context etc. ... CGContextDrawPDFPage(context, page); ... UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext(); ...//saving the image to disc CGPDFDocumentRelease(document); [pool drain]; } changes the memory usage to MEMORY BEFORE: 6 MB MEMORY DURING 1ST DOC: 9 MB MEMORY AFTER 1ST DOC: 7 MB MEMORY DURING 2ND DOC: 9 MB MEMORY AFTER 2ND DOC: 7 MB .... but is obviously a step backwards in performance. When I start reading a PDF (later in time, different thread) in the first case no more memory is allocated (staying at 25 MB), while in the second case memory goes up to 20 MB (from 7). In both cases, when I remove the CGContextDrawPDFPage(context, page); line memory is (nearly) constant at 6 MB during and after all preparations of documents. Can anybody explain whats going on there?

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  • embed a jquery script after jquery is loaded by widget

    - by matthew k
    http://stackoverflow.com/a/6065421 was helpful to see how to confirm jquery has been loaded. my widget will need a class that was written using jquery. may i have some assistance on embedding this other class built using jquery? thank you, below is the snippet from the above link with my code added in the final portion as noted in the code comments: (function(window, document, version, callback) { var j, d; var loaded = false; if (!(j = window.jQuery) || version > j.fn.jquery || callback(j, loaded)) { var script = document.createElement("script"); script.type = "text/javascript"; script.src = "/media/jquery.js"; script.onload = script.onreadystatechange = function() { if (!loaded && (!(d = this.readyState) || d == "loaded" || d == "complete")) { callback((j = window.jQuery).noConflict(1), loaded = true); j(script).remove(); } }; document.documentElement.childNodes[0].appendChild(script) } })(window, document, "1.3", function($, jquery_loaded) { //my code added below var script_tag = document.createElement('script'); script_tag.setAttribute("type","text/javascript"); script_tag.setAttribute("src", "http://mysite.com/widget/slides.jquery.js"); (document.getElementsByTagName("head")[0] || document.documentElement).appendChild(script_tag); $('#slides').slides({}); //this line gives an error. }); right now, i am trying the following based on the response(s) provided to this question (line that throws error is noted with a comment): //this function is called after jquery being embedded has been confirmed. {mysite} placeholder is nonexistent in actual code. function main() { jQuery(document).ready(function($) { var css_link = $("<link>", { rel: "stylesheet", type: "text/css", href: "http://mysite/widget/widget.css" }); css_link.appendTo('head'); $('#crf_widget').after('<div id="crf_widget_container"></div>'); /******* Load HTML *******/ var jsonp_url = "http://mysite/widget.php?callback=?"; $.getJSON(jsonp_url, function(data) { $('#crf_widget_container').html(data); $('#category_sel').change(function(){ alert(this.value); }); $.getScript("http://mysite/widget/slides.jquery.js", function(data, textStatus, jqxhr) { alert(1); //fires ok $('#slides').slides({}); //errors }); }); }); }

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  • how to count checked checkboxes in different divs

    - by KMKMAHESH
    <head><title>STUDENT WISE EXAM BACKLOGS DISPLAY FOR EXAM REGISTRATION</title> <style type="text/css"> th { font-family:Arial; color:black; border:1px solid #000; } thead { display:table-header-group; } tbody { display:table-row-group; } td { border:1px solid #000; } </style> <script type="text/javascript" > function check_value(year,sem){ ysem="ys"+year+sem; var reg=document.registration.regulation.value; subjectsys="subjects"+year+sem; amountsys="amount"+year+sem; if(year==1){ if(sem==1){ var value_list = document.getElementById("ys11").getElementsByTagName('input'); } if(sem==2){ var value_list = document.getElementById("ys12").getElementsByTagName('input'); } }elseif(year==2){ if(sem==1){ var value_list = document.getElementById("ys21").getElementsByTagName('input'); } if(sem==2){ var value_list = document.getElementById("ys22").getElementsByTagName('input'); } }elseif(year==3){ if(sem==1){ var value_list = document.getElementById("ys31").getElementsByTagName('input'); } if(sem==2){ var value_list = document.getElementById("ys32").getElementsByTagName('input'); } }elseif(year==4){ if(sem==1){ var value_list = document.getElementById("ys41").getElementsByTagName('input'); } if(sem==2){ var value_list = document.getElementById("ys42").getElementsByTagName('input'); } } values = 0; for (var i=0; i<value_list.length; i++){ if (value_list[i].checked) { values=values+1; } } document.getElementById(subjectsys).value=values; if (values=="0") { document.getElementById(amountsys).innerHTML=""; return; } if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari xmlhttp=new XMLHttpRequest(); } else {// code for IE6, IE5 xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); } xmlhttp.onreadystatechange=function() { if (xmlhttp.readyState==4 && xmlhttp.status==200) { document.getElementById(amountsys).innerHTML=xmlhttp.responseText; } } xmlhttp.open("GET","fee.php?year="+year+"&reg="+reg+"&sem="+sem+"&sub="+values,true); xmlhttp.send(); } </script> </head> <form id="registration" name="registration" action=subverify.php method=POST></br></br> <center> Backlog Subjects for <b>08KN1A1219</b> </br></br> <table border='1'><tr> <th width='40'>&nbsp;</th><th width='90'>Regulation</th><th width='40'>Year</th> <th width='40'>Sem</th><th width='350'>Subname</th> <th width='70'>Internals</th><th width='70'>Externals</th> </tr><div id="ys41"><tr> <td width='40'><center><input type="checkbox" name="sub[]" value="344" onclick="check_value(4,1)"></center></td> <td width='90'><center>R07</center></td><td width='40'><center>4</center></td><td width='40'><center>1</center></td> <td width='350'>EMBEDDED SYSTEMS</td><td width='70'><center>18</center></td> <td width='70'><center>17</center></td></tr><tr><td colspan=5 align=right><b>Subjects: </b><input size=2 type=textbox id=subjects41 name=subjects41 value=0 maxlength=2 readonly=readonly></td> <td align=right><b>Amount :</b></td> <input type='hidden' name='regulation' id=regulationsubjects41 value='R07'> <td><div id="amount41"><input type="textbox" name="amountval41" value="0" size="5" maxlength="5" readonly="readonly"></div></td></tr></div><div id="ys42"><tr> <td width='40'><center><input type="checkbox" name="sub[]" value="527" onclick="check_value(4,2)"></center></td> <td width='90'><center>R07</center></td><td width='40'><center>4</center></td><td width='40'><center>2</center></td> <td width='350'>DESIGN PATTERNS</td><td width='70'><center>12</center></td> <td width='70'><center>14</center></td></tr><tr><td colspan=5 align=right><b>Subjects: </b><input size=2 type=textbox id=subjects42 name=subjects42 value=0 maxlength=2 readonly=readonly></td> <td align=right><b>Amount :</b></td> <input type='hidden' name='regulation' id=regulationsubjects42 value='R07'> <td><div id="amount42"><input type="textbox" name="amountval42" value="0" size="5" maxlength="5" readonly="readonly"></div></td></tr></div><tr><td colspan=7><center><b><div id="maintotal"><input type="textbox" name="maintotal" value="0" size="5" maxlength="5" readonly="readonly"></div></center></b></td></tr><tr></tr></table></br></br> <center><input type='hidden' name='htno' value='08KN1A1219'> <input type='submit' value='Register'></center></form></br> this is a output of a php file with using dynamic data in the form i want to count only the checkboxes in the div and it has to display in that subjectsdiv like subjects41 and subjects42 can any one please help me to update this javascript it passes some ajax request for displaying the fee

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  • Download file using ajax and webservice

    - by megabyte
    Hi All There is this 3rd party webservice. One of the public webmethods available is a GetDocument() method. This method returns a Document object. The Document object has properties for File(byte[]), ContentType(string) ect. My Question : Can I subscribe to this service using javascript(mootools) + ajax + JSON, return the document object, in this case an excel document, and force the file download?

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  • Javascript: How to calculate the exact position of the viewport?

    - by batmanfu
    My problem is I need to get the position of the viewport relative to the extent of the entire document. I am only concerned with Firefox. My issue is that everything I have read says that: viewport height is window.innerHeight scroll position is window.pageYOffset document total height is document.height So, I would expect that if I scrolled to the bottom of a page that window.innerHeight + window.pageYOffset = document.height But it doesn't! Can someone please explain to me why this is?

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  • Call a Firebug command from client code.

    - by ProfK
    I would like to apply some sort of IoC, with debugee code, i.e. the current HTML document, and the debugger, Firebug. It would be great to have some sort of document that asks Firebug to open a push channel from the document, versus the more common scenario of the debugger pulling information from the debugee document. Is this possible and or feasible?

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  • unable to trigger event in IE during clonning

    - by Abhimanyu
    Following is the code which will clone a set of div with their events(onclick) which is working fine for FF but in case of IE it is not firing events associated with each div. <html> <head> <style type='text/css'> .firstdiv{ border:1px solid red; } </style> <script language="JavaScript"> function show_tooltip(idx,condition,ev) { alert(idx +"=="+condition+"=="+ev); } function createCloneNode () { var cloneObj = document.getElementById("firstdiv").cloneNode(true); document.getElementById("maindiv").appendChild(cloneObj); } function init(){ var mainDiv = document.createElement("div"); mainDiv.id = 'maindiv'; var firstDiv = document.createElement("div"); firstDiv.id ='firstdiv'; firstDiv.className ='firstdiv'; for(var j=0;j<4;j++) { var summaryDiv = document.createElement("div"); summaryDiv.id = "sDiv"+j summaryDiv.className ='summaryDiv'; summaryDiv.onmouseover = function() {this.setAttribute("style","text-decoration:underline;cursor:pointer;");} summaryDiv.onmouseout = function() {this.setAttribute("style","text-decoration:none;");} summaryDiv.setAttribute("onclick", "show_tooltip("+j+",'view_month',event)"); summaryDiv.innerHTML = 'Div'+j; firstDiv.appendChild(summaryDiv); } mainDiv.appendChild(firstDiv); var secondDiv = document.createElement("div"); var linkDiv = document.createElement("div"); linkDiv.innerHTML ='create clone of above element'; linkDiv.onclick = function() { createCloneNode(); } secondDiv.appendChild(linkDiv); mainDiv.appendChild(secondDiv); document.body.appendChild(mainDiv); } </script> </head> <body> <script language="JavaScript"> init() </script> </body> </html> can anybody tell me whats the problem in above code please correct me..

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  • Cocoa Scripting Bridge and <contents> element

    - by Stephen
    So, the application I'm trying to script has a scripting definition file that includes a <contents> element, which is an "implicitly specified container." The question, how do I get at what's inside this element using Scripting Bridge? Or alternatively, how do I send the Apple Event necessary to retrieve it and then transform what I get back into an SBObject? I already tried: [document nameOfKey] document.nameofKey [document contents] document.contents

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  • Python and ReportLab: add a string at the end of every page

    - by user608341
    Hi peoples, I'm building a pdf document with reportlab, using the Paragraph class: doc = SimpleDocTemplate(response, leftMargin=lateral_margin, rightMargin=lateral_margin, topMargin=top_bottom_margin, bottomMargin=top_bottom_margin) Document = [] Document.append(Paragraph("bla bla bla bla", my_style)) doc.build(Document) Now I want to add at the end of every page a string, how can I do that??

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  • .NET Efficient way to generate WORD Doc - Server Side

    - by alexbf
    Hello, .NET 4.0 I am looking for the easiest way to generate a Word document on our server. Limitations : Server side I don't want to install word on the server Data source is XML I tried to generate a DOCX with XSLT which is fast and easy but the only way I could find to validate the generated document is to open it with Word and the only error I get when the document is not valid is "Error while opening document". Not very useful. Any ideas? Thanks, Alex

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  • Keep data with specific value on top when sorting a gridview

    - by aspNetAficionado
    Hi i have a gridview with information about documents: name, document type (policy, guidelines, forms, etc), category, etc. I want to sort the gridview alphabetically (name) and by document type, but always having the 'policy' above the other document types when document name is the same. How do I do that? eg If I do sort by DocumentName, DocumentType ('policy' maybe not be the first one in the list) but if I do sort by DocumentType , DocumentName (I would get for example all guidelines first in alphabetical order, then procedures, then policies, etc)

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  • PHP PowerPoint with kohana 3 got encoding errors

    - by Jabeen
    I have just downloaded the fresh copy of phppowerpoint and added the following line of code 'phppowerpoint' = MODPATH.'phppowerpoint', and now my page got blank and I got the following error: The character encoding of the HTML document was not declared. The document will render with garbled text in some browser configurations if the document contains characters from outside the US-ASCII range. The character encoding of the page must to be declared in the document or in the transfer protocol. Any thoughts? Thanks.

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  • jQuery Sales Tax

    - by CKallemeres
    Hello everyone! I have created a function (see below) that calculates a 7.5% sales tax. Now I need help doing the following: Have totalTax() take in 2 arguments one for the price and one for the tax. On submit (use the onSubmit event handler to call this function) have the function process the price and the tax by manipulating the arguments you passed in. Have the sales tax on the page update dynamically with what ever the sales tax is that you defined for the function 7.5 percent sales tax: Instead of using .innerHTML use jQuery to access these document elements and write to them: document.getElementById('requestedAmount' ).innerHTML = priceInput; document.getElementById('requestedTax' ).innerHTML = salesTax; document.getElementById('requestedTotal' ).innerHTML = totalAmount; Original Code: <script type="text/javascript"> $().ready(function() { // validate the comment form when it is submitted $("#inputForm").validate(); $("#priceInput").priceFormat({ prefix: '', limit: 5, centsLimit: 2 }); }); function totalTax(){ var priceInput = document.getElementById( 'priceInput' ).value; var salesTax = Math.round(((priceInput / 100) * 7.5)*100)/100; var totalAmount = (priceInput*1) + (salesTax * 1); document.getElementById( 'requestedAmount' ).innerHTML = priceInput; document.getElementById( 'requestedTax' ).innerHTML = salesTax; document.getElementById( 'requestedTotal' ).innerHTML = totalAmount; } </script> <body> <form class="cmxform" id="inputForm" method="get" action=""> <p> <label for="priceInput">Enter the price: </label> <input id="priceInput" name="name" class="required"/> </p> <p> <input class="submit" type="submit" value="Submit" onclick="totalTax();"/> </p> </form> <div>Entered price: <p id="requestedAmount"></p> </div> <div>7.5 percent sales tax: <p id="requestedTax"></p> </div> <div>Total: <p id="requestedTotal"> </p> </div>

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  • having problems with javascript null

    - by user165242
    I have tried rectifying the code below. But I am not able to find a solution. After executing the code, firebug says "document.getElementById(haystack.value) is null". I tried if(document.getElementById(haystack).value ==null) but it was of no use. Please help me out. var haystack=document.getElementById('city1').value; if(!document.getElementById(haystack).value) { alert("null"); } else { alert("not null"); }

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  • code doesnot delete specific extra files but deletes all, also no recursion for directory, help me t

    - by OM The Eternity
    I have to compare two folder structure and with reference of source folder I want to delete all the files/folders present in other destination folder which do not exist in reference source folder, how could i do this? $original = scan_dir_recursive('/var/www/html/copy2'); $mirror = scan_dir_recursive('/var/www/html/copy1'); function scan_dir_recursive($dir) { $all_paths = array(); $new_paths = scandir($dir); foreach ($new_paths as $path) { if ($path == '.' || $path == '..') { continue; } $path = $dir . DIRECTORY_SEPARATOR . $path; if (is_dir($path)) { $all_paths = array_merge($all_paths, scan_dir_recursive($path)); } else { $all_paths[] = $path; } } return $all_paths; } foreach($mirror as $mirr) { if($mirr != '.' && $mirr != '..') { if(!in_array($mirr, $original)) { unlink($mirr); // delete the file } } } The above code shows what i did.. Here My copy1 folder contains extra files than copy2 folders hence i need these extra files to be deleted. Below given output is are arrays of original Mirror and of difference of both.. Original Array ( [0] => /var/www/html/copy2/Copy (5) of New Text Document.txt [1] => /var/www/html/copy2/Copy of New Text Document.txt ) Mirror Array ( [0] => /var/www/html/copy1/Copy (2) of New Text Document.txt [1] => /var/www/html/copy1/Copy (3) of New Text Document.txt [2] => /var/www/html/copy1/Copy (5) of New Text Document.txt ) Difference Array ( [0] => /var/www/html/copy1/Copy (2) of New Text Document.txt [1] => /var/www/html/copy1/Copy (3) of New Text Document.txt [2] => /var/www/html/copy1/Copy (5) of New Text Document.txt ) when i iterate a loop to delete on difference array all files has to be deleted as per displayed output.. how can i rectify this.. the loop for deletion is given below. $dirs_to_delete = array(); foreach ($diff_path as $path) { if (is_dir($path)) { $dirs_to_delete[] = $path; } else { unlink($path); } } while ($dir = array_pop($dirs_to_delete)) { rmdir($dir); }

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  • What is wrong with this javascript?

    - by bala3569
    i use this javascript syntax for validating a checkbox... alert(document.getElementById("ctl00_ContentPlaceHolder1_Chkreg").checked); if (document.getElementById("ctl00_ContentPlaceHolder1_Chkreg").checked == false) { document.getElementById("ctl00_ContentPlaceHolder1_ErrorMsg").innerHTML = "please select the checkbox"; document.getElementById("ctl00_ContentPlaceHolder1_Chkreg").focus(); return false; } My alert showed me false but my if loop is not working... Any suggestion...

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  • How to change h:outputText value by JavaScript?

    - by Peter
    I already tested with 2 inputText, It runs well for example var tdate = document.getElementById('txtDate'); //h:inputText var tdt = document.getElementById('txtDateTime'); //h:inputText tdate.onchange = function(){ tdt.value = tdate.value; }; How can I change the value of " tdt " - h:outputText? var tdate = document.getElementById('txtDate'); //h:inputText var tdt = document.getElementById('txtDateTime'); //h:outputText

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  • Javascript returns Nan in IE, FF ok

    - by user350184
    im very new to javascript, and writing this script to add up a shopping cart and print out subtotals and totals. it works in FF but not in IE. this function is called by onclick of one of three select options with a value of 0-25. it is in a js file called in the head. what it does is get the selected values as variables, parseint them, adds and multiplies, and changes the innerHTML of the table to reflect the subtotals, and total. FF does it great, but IE gives Nan. ive tried rewriting it a number of different ways, and many translations still work in FF but not IE8. ive made sure the variables and form id's arent repeated. function gen_invoice() { var scount = parseInt(document.shopcart.studentcount.value, 10); var ycount = parseInt(document.shopcart.youthcount.value, 10); var fcount = parseInt(document.shopcart.facultycount.value, 10); //html output source is 3 selects like this, with diff ids and names: //<select name="studentcount" id="studentcount"> //<option onclick="gen_invoice()" value="0">0 </option></select> var cardcost = parseInt(document.shopcart.cardprice.value, 10); //cardcost comes from hidden input value: //<input type="hidden" id="cardprice" name="cardprice" value="25"> var totalsum = scount + ycount + fcount; var grandtotal = totalsum * cardcost; document.getElementById('s_price').innerHTML = scount * cardcost; document.getElementById('y_price').innerHTML = ycount * cardcost; document.getElementById('f_price').innerHTML = fcount * cardcost; document.getElementById('grand').innerHTML = grandtotal; //.... } ...after this there are 3 long loops for writing out some other forms, but they dont work in IE either because they depend on the selected values to be an integer. this part happens first and returns Nan, so im sure the problem is here somwhere. I have literally hit my head on the table over this. You can imagine how frustrating it is to be able to write the entire rest of the site beautifully, but then fail at adding 3 numbers together. help please!

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  • allignment issue of div tag

    - by Quasar the space thing
    I am trying to create a web page where on click of a button I can add div tags. What I thought to do was that I'll create two div tags within a single div so that over all presentation will be uniform and similar to a table having two columns and multiple rows and the first column contains only label's and second column will contain textbox. Here is the JS file : var counter = 0; function create_div(type){ var dynDiv = document.createElement("div"); dynDiv.id = "divid_"+counter; dynDiv.class="main"; document.body.appendChild(dynDiv); question(); if(type == 'ADDTEXTBOX'){ ADDTEXTBOX(); } counter=counter+1; } function question(){ var question_div = document.createElement("div"); question_div.class="question"; question_div.id = "question_div_"+counter; var Question = prompt("Enter The Question here:", ""); var node=document.createTextNode(Question); question_div.appendChild(node); var element=document.getElementById("divid_"+counter); element.appendChild(question_div); } function ADDTEXTBOX(){ var answer_div = document.createElement("div"); answer_div.class="answer"; answer_div.id = "answer_div_"+counter; var answer_tag = document.createElement("input"); answer_tag.id = "answer_tag_"+counter; answer_tag.setAttribute("type", "text"); answer_tag.setAttribute("name", "textbox"); answer_div.appendChild(answer_tag); var element=document.getElementById("divid_"+counter); element.appendChild(answer_div); } Here is the css file : .question { width: 40%; height: auto; float: left; display: inline-block; text-align: justify; word-wrap:break-word; } .answer { padding-left:10%; width: 40%; height: auto; float: left; overflow: auto; word-wrap:break-word; } .main { width: auto; background-color:gray; height: auto; overflow: auto; word-wrap:break-word; } My problem is that the code is working properly but both the divisions are not coming in a straight line. after the first div prints on the screen the second divisions comes in another line. How can I make both the div's come in the same line ? Thank You. PS : should I stick with the current idea of using div or should I try some other approach ? like tables ?

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  • Class-Level Model Validation with EF Code First and ASP.NET MVC 3

    - by ScottGu
    Earlier this week the data team released the CTP5 build of the new Entity Framework Code-First library.  In my blog post a few days ago I talked about a few of the improvements introduced with the new CTP5 build.  Automatic support for enforcing DataAnnotation validation attributes on models was one of the improvements I discussed.  It provides a pretty easy way to enable property-level validation logic within your model layer. You can apply validation attributes like [Required], [Range], and [RegularExpression] – all of which are built-into .NET 4 – to your model classes in order to enforce that the model properties are valid before they are persisted to a database.  You can also create your own custom validation attributes (like this cool [CreditCard] validator) and have them be automatically enforced by EF Code First as well.  This provides a really easy way to validate property values on your models.  I showed some code samples of this in action in my previous post. Class-Level Model Validation using IValidatableObject DataAnnotation attributes provides an easy way to validate individual property values on your model classes.  Several people have asked - “Does EF Code First also support a way to implement class-level validation methods on model objects, for validation rules than need to span multiple property values?”  It does – and one easy way you can enable this is by implementing the IValidatableObject interface on your model classes. IValidatableObject.Validate() Method Below is an example of using the IValidatableObject interface (which is built-into .NET 4 within the System.ComponentModel.DataAnnotations namespace) to implement two custom validation rules on a Product model class.  The two rules ensure that: New units can’t be ordered if the Product is in a discontinued state New units can’t be ordered if there are already more than 100 units in stock We will enforce these business rules by implementing the IValidatableObject interface on our Product class, and by implementing its Validate() method like so: The IValidatableObject.Validate() method can apply validation rules that span across multiple properties, and can yield back multiple validation errors. Each ValidationResult returned can supply both an error message as well as an optional list of property names that caused the violation (which is useful when displaying error messages within UI). Automatic Validation Enforcement EF Code-First (starting with CTP5) now automatically invokes the Validate() method when a model object that implements the IValidatableObject interface is saved.  You do not need to write any code to cause this to happen – this support is now enabled by default. This new support means that the below code – which violates one of our above business rules – will automatically throw an exception (and abort the transaction) when we call the “SaveChanges()” method on our Northwind DbContext: In addition to reactively handling validation exceptions, EF Code First also allows you to proactively check for validation errors.  Starting with CTP5, you can call the “GetValidationErrors()” method on the DbContext base class to retrieve a list of validation errors within the model objects you are working with.  GetValidationErrors() will return a list of all validation errors – regardless of whether they are generated via DataAnnotation attributes or by an IValidatableObject.Validate() implementation.  Below is an example of proactively using the GetValidationErrors() method to check (and handle) errors before trying to call SaveChanges(): ASP.NET MVC 3 and IValidatableObject ASP.NET MVC 2 included support for automatically honoring and enforcing DataAnnotation attributes on model objects that are used with ASP.NET MVC’s model binding infrastructure.  ASP.NET MVC 3 goes further and also honors the IValidatableObject interface.  This combined support for model validation makes it easy to display appropriate error messages within forms when validation errors occur.  To see this in action, let’s consider a simple Create form that allows users to create a new Product: We can implement the above Create functionality using a ProductsController class that has two “Create” action methods like below: The first Create() method implements a version of the /Products/Create URL that handles HTTP-GET requests - and displays the HTML form to fill-out.  The second Create() method implements a version of the /Products/Create URL that handles HTTP-POST requests - and which takes the posted form data, ensures that is is valid, and if it is valid saves it in the database.  If there are validation issues it redisplays the form with the posted values.  The razor view template of our “Create” view (which renders the form) looks like below: One of the nice things about the above Controller + View implementation is that we did not write any validation logic within it.  The validation logic and business rules are instead implemented entirely within our model layer, and the ProductsController simply checks whether it is valid (by calling the ModelState.IsValid helper method) to determine whether to try and save the changes or redisplay the form with errors. The Html.ValidationMessageFor() helper method calls within our view simply display the error messages our Product model’s DataAnnotations and IValidatableObject.Validate() method returned.  We can see the above scenario in action by filling out invalid data within the form and attempting to submit it: Notice above how when we hit the “Create” button we got an error message.  This was because we ticked the “Discontinued” checkbox while also entering a value for the UnitsOnOrder (and so violated one of our business rules).  You might ask – how did ASP.NET MVC know to highlight and display the error message next to the UnitsOnOrder textbox?  It did this because ASP.NET MVC 3 now honors the IValidatableObject interface when performing model binding, and will retrieve the error messages from validation failures with it. The business rule within our Product model class indicated that the “UnitsOnOrder” property should be highlighted when the business rule we hit was violated: Our Html.ValidationMessageFor() helper method knew to display the business rule error message (next to the UnitsOnOrder edit box) because of the above property name hint we supplied: Keeping things DRY ASP.NET MVC and EF Code First enables you to keep your validation and business rules in one place (within your model layer), and avoid having it creep into your Controllers and Views.  Keeping the validation logic in the model layer helps ensure that you do not duplicate validation/business logic as you add more Controllers and Views to your application.  It allows you to quickly change your business rules/validation logic in one single place (within your model layer) – and have all controllers/views across your application immediately reflect it.  This help keep your application code clean and easily maintainable, and makes it much easier to evolve and update your application in the future. Summary EF Code First (starting with CTP5) now has built-in support for both DataAnnotations and the IValidatableObject interface.  This allows you to easily add validation and business rules to your models, and have EF automatically ensure that they are enforced anytime someone tries to persist changes of them to a database.  ASP.NET MVC 3 also now supports both DataAnnotations and IValidatableObject as well, which makes it even easier to use them with your EF Code First model layer – and then have the controllers/views within your web layer automatically honor and support them as well.  This makes it easy to build clean and highly maintainable applications. You don’t have to use DataAnnotations or IValidatableObject to perform your validation/business logic.  You can always roll your own custom validation architecture and/or use other more advanced validation frameworks/patterns if you want.  But for a lot of applications this built-in support will probably be sufficient – and provide a highly productive way to build solutions. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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  • Code Contracts: Hiding ContractException

    - by DigiMortal
    It’s time to move on and improve my randomizer I wrote for an example of static checking of code contracts. In this posting I will modify contracts and give some explanations about pre-conditions and post-conditions. Also I will show you how to avoid ContractExceptions and how to replace them with your own exceptions. As a first thing let’s take a look at my randomizer. public class Randomizer {     public static int GetRandomFromRange(int min, int max)     {         var rnd = new Random();         return rnd.Next(min, max);     }       public static int GetRandomFromRangeContracted(int min, int max)     {         Contract.Requires(min < max, "Min must be less than max");           var rnd = new Random();         return rnd.Next(min, max);     } } We have some problems here. We need contract for method output and we also need some better exception handling mechanism. As ContractException as type is hidden from us we have to switch from ContractException to some other Exception type that we can catch. Adding post-condition Pre-conditions are contracts for method’s input interface. Read it as follows: pre-conditions make sure that all conditions for method’s successful run are met. Post-conditions are contracts for output interface of method. So, post-conditions are for output arguments and return value. My code misses the post-condition that checks return value. Return value in this case must be greater or equal to minimum value and less or equal to maximum value. To make sure that method can run only the correct value I added call to Contract.Ensures() method. public static int GetRandomFromRangeContracted(int min, int max) {     Contract.Requires(min < max, "Min must be less than max");       Contract.Ensures(         Contract.Result<int>() >= min &&         Contract.Result<int>() <= max,         "Return value is out of range"     );       var rnd = new Random();     return rnd.Next(min, max); } I think that the line I added does not need any further comments. Avoiding ContractException for input interface ContractException lives in hidden namespace and we cannot see it at design time. But it is common exception type for all contract exceptions that we do not switch over to some other type. The case of Contract.Requires() method is simple: we can tell it what kind of exception we need if something goes wrong with contract it ensures. public static int GetRandomFromRangeContracted(int min, int max) {     Contract.Requires<ArgumentOutOfRangeException>(         min < max,         "Min must be less than max"     );       Contract.Ensures(         Contract.Result<int>() >= min &&         Contract.Result<int>() <= max,         "Return value is out of range"     );       var rnd = new Random();     return rnd.Next(min, max); } Now, if we violate the input interface contract giving min value that is not less than max value we get ArgumentOutOfRangeException. Avoiding ContractException for output interface Output interface is more complex to control. We cannot give exception type there and hope that this type of exception will be thrown if something goes wrong. Instead we have to use delegate that gathers information about problem and throws the exception we expect to be thrown. From documentation you can find the following example about the delegate I mentioned. Contract.ContractFailed += (sender, e) => {     e.SetHandled();     e.SetUnwind(); // cause code to abort after event     Assert.Fail(e.FailureKind.ToString() + ":" + e.DebugMessage); }; We can use this delegate to throw the Exception. Let’s move the code to separate method too. Here is our method that uses now ContractException hiding. public static int GetRandomFromRangeContracted(int min, int max) {     Contract.Requires(min < max, "Min must be less than max");       Contract.Ensures(         Contract.Result<int>() >= min &&         Contract.Result<int>() <= max,         "Return value is out of range"     );     Contract.ContractFailed += Contract_ContractFailed;       var rnd = new Random();     return rnd.Next(min, max)+1000; } And here is the delegate that creates exception. public static void Contract_ContractFailed(object sender,     ContractFailedEventArgs e) {     e.SetHandled();     e.SetUnwind();       throw new Exception(e.FailureKind.ToString() + ":" + e.Message); } Basically we can do in this delegate whatever we like to do with output interface errors. We can even introduce our own contract exception type. As you can see later then ContractFailed event is very useful at unit testing.

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  • Building extensions for Expression Blend 4 using MEF

    - by Timmy Kokke
    Introduction Although it was possible to write extensions for Expression Blend and Expression Design, it wasn’t very easy and out of the box only one addin could be used. With Expression Blend 4 it is possible to write extensions using MEF, the Managed Extensibility Framework. Until today there’s no documentation on how to build these extensions, so look thru the code with Reflector is something you’ll have to do very often. Because Blend and Design are build using WPF searching the visual tree with Snoop and Mole belong to the tools you’ll be using a lot exploring the possibilities.  Configuring the extension project Extensions are regular .NET class libraries. To create one, load up Visual Studio 2010 and start a new project. Because Blend is build using WPF, choose a WPF User Control Library from the Windows section and give it a name and location. I named mine DemoExtension1. Because Blend looks for addins named *.extension.dll  you’ll have to tell Visual Studio to use that in the Assembly Name. To change the Assembly Name right click your project and go to Properties. On the Application tab, add .Extension to name already in the Assembly name text field. To be able to debug this extension, I prefer to set the output path on the Build tab to the extensions folder of Expression Blend. This means that everything that used to go into the Debug folder is placed in the extensions folder. Including all referenced assemblies that have the copy local property set to false. One last setting. To be able to debug your extension you could start Blend and attach the debugger by hand. I like it to be able to just hit F5. Go to the Debug tab and add the the full path to Blend.exe in the Start external program text field. Extension Class Add a new class to the project.  This class needs to be inherited from the IPackage interface. The IPackage interface can be found in the Microsoft.Expression.Extensibility namespace. To get access to this namespace add Microsoft.Expression.Extensibility.dll to your references. This file can be found in the same folder as the (Expression Blend 4 Beta) Blend.exe file. Make sure the Copy Local property is set to false in this reference. After implementing the interface the class would look something like: using Microsoft.Expression.Extensibility; namespace DemoExtension1 { public class DemoExtension1:IPackage { public void Load(IServices services) { } public void Unload() { } } } These two methods are called when your addin is loaded and unloaded. The parameter passed to the Load method, IServices services, is your main entry point into Blend. The IServices interface exposes the GetService<T> method. You will be using this method a lot. Almost every part of Blend can be accessed thru a service. For example, you can use to get to the commanding services of Blend by calling GetService<ICommandService>() or to get to the Windowing services by calling GetService<IWindowService>(). To get Blend to load the extension we have to implement MEF. (You can get up to speed on MEF on the community site or read the blog of Mr. MEF, Glenn Block.)  In the case of Blend extensions, all that needs to be done is mark the class with an Export attribute and pass it the type of IPackage. The Export attribute can be found in the System.ComponentModel.Composition namespace which is part of the .NET 4 framework. You need to add this to your references. using System.ComponentModel.Composition; using Microsoft.Expression.Extensibility;   namespace DemoExtension1 { [Export(typeof(IPackage))] public class DemoExtension1:IPackage { Blend is able to find your addin now. Adding UI The addin doesn’t do very much at this point. The WPF User Control Library came with a UserControl so lets use that in this example. I just drop a Button and a TextBlock onto the surface of the control to have something to show in the demo. To get the UserControl to work in Blend it has to be registered with the WindowService.  Call GetService<IWindowService>() on the IServices interface to get access to the windowing services. The UserControl will be used in Blend on a Palette and has to be registered to enable it. This is done by calling the RegisterPalette on the IWindowService interface and passing it an identifier, an instance of the UserControl and a caption for the palette. public void Load(IServices services) { IWindowService windowService = services.GetService<IWindowService>(); UserControl1 uc = new UserControl1(); windowService.RegisterPalette("DemoExtension", uc, "Demo Extension"); } After hitting F5 to start debugging Expression Blend will start. You should be able to find the addin in the Window menu now. Activating this window will show the “Demo Extension” palette with the UserControl, style according to the settings of Blend. Now what? Because little is publicly known about how to access different parts of Blend adding breakpoints in Debug mode and browsing thru objects using the Quick Watch feature of Visual Studio is something you have to do very often. This demo extension can be used for that purpose very easily. Add the click event handler to the button on the UserControl. Change the contructor to take the IServices interface and store this in a field. Set a breakpoint in the Button_Click method. public partial class UserControl1 : UserControl { private readonly IServices _services;   public UserControl1(IServices services) { _services = services; InitializeComponent(); }   private void button1_Click(object sender, RoutedEventArgs e) { } } Change the call to the constructor in the load method and pass it the services property. public void Load(IServices services) { IWindowService service = services.GetService<IWindowService>(); UserControl1 uc = new UserControl1(services); service.RegisterPalette("DemoExtension", uc, "Demo Extension"); } Hit F5 to compile and start Blend. Got to the window menu and start show the addin. Click on  the button to hit the breakpoint. Now place the carrot text _services text in the code window and hit Shift+F9 to show the Quick Watch window. Now start exploring and discovering where to find everything you need.  More Information The are no official resources available yet. Microsoft has released one extension for expression Blend that is very useful as a reference, the Microsoft Expression Blend® Add-in Preview for Windows® Phone. This will install a .extension.dll file in the extension folder of Blend. You can load this file with Reflector and have a peek at how Microsoft is building his addins. Conclusion I hope this gives you something to get started building extensions for Expression Blend. Until Microsoft releases the final version, which hopefully includes more information about building extensions, we’ll have to work on documenting it in the community.

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