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• How can I intelligently group rows of integers for a faceted search?

  - by Alastair

  I'm not even quite sure what terms I should be using for what I want, so any advice on what I'm even asking for would be very welcome. Basically, my web site lists user-generated accommodations. Each has a rent price, which users will be able to query in our new faceted search box. Users search by city, and within each city I'd like to present a different rent grouping. That is to say that in City #1, if we have listings ranging from $200 - $1000, I'd like to present checkboxes for: less than $300 $301 - $500 $501 - $700 more than $700 However, if City #2 has values that range from $500 - $1500, I want the ranges above to change accordingly. So, if I say that I want 5 or 6 range options in each city, I think I have two options: Take the min and max values and just split the difference. I don't like this idea because one listing with a rent of $10,000 will throw the whole scale off. Intelligently calculate the ranges using means, medians etc. Number 2 is what I need help with. I'm a web developer that gets logic, but was never strong on math and statistics at school. Can anyone point me towards a guide that'll help me figure this out?

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• Google App Engine - How to implement the activity stream in a social network

  - by spidee

  I want some ideas on the best practice to implement an activity stream for a social network im building in app engine (PYTHON) I first want to keep a log for all activities of each user - so that we have a history. i.e. someone became a friend, added a picture, changed their address etc. This way we have a users history available should we need it. Also mean we can remove friendship joins, change user data but have a historical log. I also want to stream a users activity to their friends. for this only the last X activities need to be kept - that is in the scenario that messages are sent to friends when an activity occurs. Its pretty straight forward designing a history log - ie: when, what, where. The complication comes as to how we notify friends of a user as to their activity. In our app friendships are not mutual - ie they are based on the twitter following model. Some accounts could have thousands of followers. What is the best approach to model this. using a many to many join table and doing a costly query - using a feed class that fired a copy of the activity to all the subscribers - maybe into mcache? As their maybe a need to fire thousands of messages i would imagine a cron job would need to be used. Any help ideas thoughts on this Thx

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• How to Parse an XML (using XELement) having multiple Namespace ?

  - by Subhen

  Hi I , I get the followinng Xresponse after parsing the XML document: <DIDL-Lite xmlns="urn:schemas-upnp-org:metadata-1-0/DIDL-Lite/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:upnp="urn:schemas-upnp-org:metadata-1-0/upnp/" xmlns:dlna="urn:schemas-dlna-org:metadata-1-0/"> <item id="1182" parentID="40" restricted="1"> <title>Hot Issue</title> </item> As per the earlier thread, When there is a default namespace in the document, you must parse it as if it were a named namespace. For example. XNamespace ns = "urn:schemas-upnp-org:metadata-1-0/DIDL-Lite/"; var xDIDL = xResponse.Element(ns + "DIDL-Lite"); But in my case I have four different name space. I am not getting any results after using the following query , I am getting the response , Not Yeilding any results: XNamespace dc = "http://purl.org/dc/elements/1.1/"; var vAudioData = from xAudioinfo in xResponse.Descendants(ns + "DIDL-lite").Elements("item") select new RMSMedia { strAudioTitle = ((string)xAudioinfo.Element(dc + "title")).Trim(), }; I have no clue whats going on as am new to it. Please help

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• What's the best way to transfer a large dataset over a .NET web service?

  - by Malvineous

  I've inherited a C# .NET application which talks to a web service, and the web service talks to an Oracle database. I need to add an export function to the UI, to produce an Excel spreadsheet of some of the data. I have created a web service function to run a database query, load the data into a DataTable and then return it, which works fine for a small number of rows. However there is enough data in the full run that the client application locks up for a few minutes and then returns a timeout error. Obviously this isn't the best way to retrieve such a large dataset. Before I go ahead and come up with some dodgy way of splitting the call, I'm wondering if there is already something in place that can handle this. At the moment I'm thinking of a startExport function then repeatedly calling a next50Rows function until there is no data left, but because web services are stateless this means I'm going to have to keep some sort of ID number around and deal with the associated permissions. It would mean that I don't have to load the entire data set into the web server's memory though, which is one good thing. So if anyone knows a better way to retrieve a large amount of data (in a table format) over a .NET web service, please let me know!

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• How do I keep users from spoofing data through a form?

  - by Jonathan

  I have a site which has been running for some time now that uses a great deal of user input to build the site. Naturally there are dozens of forms on the site. When building the site, I often used hidden form fields to pass data back to the server so that I know which record to update. an example might be: <input type="hidden" name="id" value="132" /> <input type="text" name="total_price" value="15.02" /> When the form is submitted, these values get passed to the server and I update the records based on the data passed (i.e. the price of record 132 would get changed to 15.02). I recently found out that you can change the attributes and values via something as simple as firebug. So...I open firebug and change the id value to "155" and the price value to "0.00" and then submit the form. Viola! I view product number 155 on the site and it now says that it's $0.00. This concerns me. How can I know which record to update without either a query string (easily modified) or a hidden input element passing the id to the server? And if there's no better way (I've seen literally thousands of websites that pass the data this way), then how would I make it so that if a user changes these values, the data on the server side is not executed (or something similar to solve the issue)? I've thought about encrypting the id and then decrypting it on the other side, but that still doesn't protect me from someone changing it and just happening to get something that matches another id in the database. I've also thought about cookies, but I've heard that those can be manipulated as well. Any ideas? This seems like a HUGE security risk to me.

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• Product Name Print Several times, How to fix.?

  - by mans

  i had added the following Opencart module for my order report list... http://www.opencart.com/index.php?route=extension/extension/info&extension_id=3597&filter_search=order%20list%20filter%20model&page=4 I have problems with the column "Products". If there are more than one option the products name prints several times. So if I got a product with three options the product name prints three times. Is there any way to fix this problem? i want print product name and model number only once, any idea.? i will attach the results what i got now... this is my sql query... public function getOrders($data = array()) { $sql = "select o.order_id,o.email,o.telephone,CONCAT(o.shipping_address_1, ' ', o.shipping_address_2) AS address,CONCAT(o.firstname, ' ', o.lastname) AS customer,o.payment_zone AS state,o.payment_address_2 AS block, o.payment_address_1 AS address,o.payment_postcode AS postcode,(SELECT os.name FROM " . DB_PREFIX . "order_status os WHERE os.order_status_id = o.order_status_id AND os.language_id = '" . (int)$this->config->get('config_language_id') . "') AS status,o.payment_city AS city,GROUP_CONCAT(pd.name) AS pdtname,GROUP_CONCAT(op.model) AS model,o.date_added,sum(op.quantity) AS quantity,GROUP_CONCAT(opt.value ) AS options, GROUP_CONCAT(opt.order_product_id ) AS ordprdid,GROUP_CONCAT(op.order_product_id ) AS optprdid, GROUP_CONCAT(op.quantity) AS opquantity from `" . DB_PREFIX . "order` o LEFT JOIN " . DB_PREFIX . "order_product op ON (op.order_id = o.order_id) LEFT JOIN " . DB_PREFIX . "product_description pd ON (pd.product_id = op.product_id and pd.language_id = '" . (int)$this->config->get('config_language_id') . "') LEFT JOIN " . DB_PREFIX . "order_option opt ON (opt.order_product_id = op.order_product_id) "; Product Name = GROUP_CONCAT(pd.name) AS pdtname,

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• IPad SQLite Push and Pull Data from external MS SQL Server DB

  - by MattyD

  This carries on from my previous post (http://stackoverflow.com/questions/4182664/ipad-app-pull-and-push-relational-data). My plan is that when the ipad application starts I am going to pull data (config data i.e. Departments, Types etc etc relational data that is used across the system) from a webhosted MS SQL Server DB via a webservice and populate it into an SQL Lite DB on the IPad. Then when I load a listing I will pull the data over the line again via a webservice and populate it into the SQL Lite db on the ipad (than just run select commands to populate the listing). My questions are: 1. What is the most efficient way to transfer data across the line via the web? Everyone seems to do it a different way. My idea is that I will have a webService for each type of data pull (e.g. RetrieveContactListing) that will query the db and than convert that data into "something" to send across the line. My question really is what is the "something" that it should be converting into? 2. Everyone talks about odata services. Is this suited for applications where complex read and writes are needed? Ive created a simple iphone app before that talked to an sql server db (i just sent my own structured xml across the line) but now with this app the data calls are going to be a lot larger so efficiency is key.

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• Cant render a .avi file

  - by Manish

  Hi, This is my 3rd post regarding this issue of cropping a file into smaller (same format files) .Please some one help me with this.Here is my code : CoInitialize(NULL); //Create the FGM CoCreateInstance(CLSID_FilterGraph,NULL,CLSCTX_INPROC_SERVER,IID_IGraphBuilder,(void**)(&pGraphBuilder)); //Query the Interfaces pGraphBuilder->QueryInterface(IID_IMediaControl,(void**)&pMediaControl); pGraphBuilder->QueryInterface(IID_IMediaEvent,(void**)&pMediaEvent); pGraphBuilder->QueryInterface(IID_IMediaPosition,(void**)&pMediaPosition); //Adding a Filewriter before calling the renderfile IBaseFilter *pWriter=NULL; IFileSinkFilter *pSink=NULL; CoCreateInstance(CLSID_FileWriter,NULL,CLSCTX_INPROC_SERVER,IID_PPV_ARGS(&pWriter)); pWriter->QueryInterface(IID_IFileSinkFilter,(void**)&pSink); pSink->SetFileName(OUTFILE,NULL); //Create a source filter IBaseFilter* pSource=NULL; HRESULT hr11=pGraphBuilder->AddSourceFilter(FILENAME,L"Source",&pSource); //Create a AVI mux IBaseFilter *pAVImux; CoCreateInstance(CLSID_AviDest,NULL,CLSCTX_INPROC_SERVER,IID_PPV_ARGS(&pAVImux)); pGraphBuilder->AddFilter(pAVImux,L"AVI Mux"); pGraphBuilder->AddFilter(pWriter,L"File Writer"); //Connect Source and Mux IEnumPins* pEnum1=NULL; IPin* pPin1=NULL; IEnumPins *pEnum2=NULL; IPin *pPin2=NULL; pSource->EnumPins(&pEnum1); pEnum1->Next(1,&pPin1,NULL); HRESULT hr1=ConnectFilters(pGraphBuilder,pPin1,pAVImux); //Mux to Writer HRESULT hr4=ConnectFilters(pGraphBuilder,pAVImux,pWriter); //Render the input file HRESULT hr3=pGraphBuilder->RenderFile(FILENAME,NULL); //Set Display times pMediaPosition->put_CurrentPosition(0); pMediaPosition->put_StopTime(2); //Run the graph HRESULT hr=pMediaControl->Run(); On running no video is shown. All the hresults return S_OK .A .avi file( larger than original is created) and I cannot play that file.

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• SQL: How to Return One DB Row from Two That Have The Same Values In Opposite Columns Using the MAX F

  - by OneSource

  Hi, This is what I'm trying to do. I have three columns in a table - ID, Column1, Column2 - with this example data: ID Column1 Column2 1     1            2 2     2            1 3     4            3 4     3            4 Since, in the first two rows, Column1 and Column2 have the same values (but in different columns), I want my MAX query to return an ID of 2. Same thing with rows 3 and 4 .... since Columns 1 and 2 have the same values (but in different columns), I want MAX(ID) to return 4. Of course, with MAX, you use Group By, but that will not work in my case. In effect, I need a Group By to work across two columns. Is this possible? If not, what's the best way to accomplish getting the IDs of 2 and 4 given the matching values that are in different columns? Thanks!

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• UIImageView Centering Problem.

  - by sagar

  To understand my problem let's follow this steps. Open - XCode - New Project - View based application. Open View Controller.xib file. Drag an image-view into viewController's view. Place that image view on center of viewController's view. Apply size of 125x125 to image-view. Take any image with dimension of 320 width & 460 height. Drag that image into your application resources directory. Now, Again back to .xib File & select image-view Set image (which is in your resources) to image-view Set Image-view Mode to - Center Ok. Let me explain the situation now. after performing all above steps - image-view has an image which is larger than image-view's size. However, Image-view places that image on center & in View controller image-view is looking proper ( not scaled ). But When you run your application, image-view will be displayed in size of 320x460. ( but it is not actually scaled. ) Now, I can't find the reason, why interface builder is displaying something else & simulator/iphone is displaying something else ? My Query. I want the image's center portion within image-view no matter what image size is. Thanks in advance for sharing your knowledge. Sagar.

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• How to compare a string with an option value

  - by user225269

  I have this html form which has options: <tr> <td width="30" height="35"><font size="3">*List:</td> <td width="30"><input name="specific" type="text" id="specific" maxlength="25" value=""> </td> <td><font size="3">*By:</td> <td> <select name="general" id="general"> <font size="3"> <option value="YEAR">Year</option> <option value="ADDRESS">Address</option> </select></td></td> </tr> And I'm trying to have this as the form action: if ('{$_POST["ADDRESS"]}'="ADDRESS") Which will compare if the value in the option in the html form matches the word "Address". If it matches then it will execute this query: $saddress= mysql_real_escape_string($_POST['specific']);<--this is the input form where the user will put the specific address to search. mysql_query("SELECT * FROM student WHERE ADDRESS='$saddress'"); Please I need help in here, I thinks its wrong: if ('{$_POST["ADDRESS"]}'="ADDRESS")

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• Howto use predicates in LINQ to Entities for Entity Framework objects

  - by user274947

  I'm using LINQ to Entities for Entity Framework objects in my Data Access Layer. My goal is to filter as much as I can from the database, without applying filtering logic on in-memory results. For that purpose Business Logic Layer passes a predicate to Data Access Layer. I mean Func<MyEntity, bool> So, if I use this predicate directly, like public IQueryable<MyEntity> GetAllMatchedEntities(Func<MyEntity, Boolean> isMatched) { return qry = _Context.MyEntities.Where(x => isMatched(x)); } I'm getting the exception [System.NotSupportedException] --- {"The LINQ expression node type 'Invoke' is not supported in LINQ to Entities."} Solution in that question suggests to use AsExpandable() method from LINQKit library. But again, using public IQueryable<MyEntity> GetAllMatchedEntities(Func<MyEntity, Boolean> isMatched) { return qry = _Context.MyEntities.AsExpandable().Where(x => isMatched(x)); } I'm getting the exception Unable to cast object of type 'System.Linq.Expressions.FieldExpression' to type 'System.Linq.Expressions.LambdaExpression' Is there way to use predicate in LINQ to Entities query for Entity Framework objects, so that it is correctly transformed it into a SQL statement. Thank you.

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• MySQL Database is Indexed at Apache Solr, How to access it via URL

  - by Wasim

  data-config.xml <dataConfig> <dataSource encoding="UTF-8" type="JdbcDataSource" driver="com.mysql.jdbc.Driver" url="jdbc:mysql://localhost:3306/somevisits" user="root" password=""/> <document name="somevisits"> <entity name="login" query="select * from login"> <field column="sv_id" name="sv_id" /> <field column="sv_username" name="sv_username" /> </entity> </document> </dataConfig> schema.xml <?xml version="1.0" encoding="UTF-8" ?> <schema name="example" version="1.5"> <fields> <field name="sv_id" type="string" indexed="true" stored="true" required="true" multiValued="false" /> <field name="username" type="string" indexed="true" stored="true" required="true"/> <field name="_version_" type="long" indexed="true" stored="true" multiValued="false"/> <field name="text" type="string" indexed="true" stored="false" multiValued="true"/> </fields> <uniqueKey>sv_id</uniqueKey> <types> <fieldType name="string" class="solr.StrField" sortMissingLast="true" /> <fieldType name="long" class="solr.TrieLongField" precisionStep="0" positionIncrementGap="0"/> </types> </schema> Solr successfully imported mysql database using full http://[localSolr]:8983/solr/#/collection1/dataimport?command=full-import My question is, how to access that mysql imported database now?

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• Modifying SQL Database on Shared Hosting

  - by apocalypse9

  I have a live database on a shared hosting server. I am making some major changes to my site's code and I would like to fix some stupid mistakes I made in initially designing the database. These changes involve altering the size of a large number of fields, and enforcing referential integrity between tables properly. I would like to make the changes on both my local test server and the remote server if possible. I should note that while I'm fairly comfortable with writing complex queries to handle data, I have very little experience modifying database structure without a graphical interface. I can access the remote database in the visual studio database explorer but I can not use that for anything other than data manipulation. I installed Sql Management Studio express last night and after 40+ crashes I gave up - I couldn't even patch the damn thing. The remote server is SQL 2005 / The MyLittleAdmin web interface is available. So my question is what is the best way to accomplish these changes. Is there a graphical interface I can use on the remote server? If not is there an easy way to copy the database to my local machine, fix it, and re upload? Finally if none of the above are viable does anyone have links to a decent info on fixing referential integrity via query? Sorry for the somewhat general question - I feel like I am making this far harder than it should be but after searching / trying all night i haven't gotten anywhere. Thanks in advance for the help. I really appreciate it. ...Also does anyone have a time machine I can borrow- I need to go kick my past self's ass for this.

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• [MySQL] Efficiently store last X records per item

  - by Saif Bechan

  I want to store the last X records in an MySQL database in an efficient way. So when the 4th record is stored the first should be deleted. The way I do this not is first run a query getting the items. Than check what I should do then insert/delete. There has to be a better way to do this. Any suggestions? Edit I think I should add that the records stored do not have a unique number. They have a mixed par. For example article_id and user_id. Then I want to make a table with the last X items for user_x. Just selecting the article from the table grouped by user and sorted by time is not an option for me. The table where I do the sort and group on has millions of records and gets hit a lot for no reason. So making a table in between with the last X records is way more effient. PS. I am not using this for articles and users.

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• How can I make Access think there is a primary key

  - by user3692757

  I have a table and I'm trying to join it with another table, but it doesn't have a distinctive primary key. The two tables do share similarities, “Acct” and “Location”. If I could concatenate “Acct&Location” it would become a primary key, but Access won’t let me make a primary key from a calculation. I provided a small sample below. Each hospital has an “Acct”, but the “Acct” will show up once for each “Location”. How can I make join these in a relationship? I connected the two in a relationships and tried to “Enforce Referential Integrity”, but it indicated “No unique index found for the referenced field of the primary key”. Also, if I run a “Find UnMatched Query” it doesn’t find anything. I think its because I can’t make it realize that in combination “Acct” and “Location” can be perceived as primary keys when used in conjunction of each other. Acct 1 2 3 1 2 3 1 2 3| Location ABI ABI ABI NHO NHO NHO NTX NTX NTX I tried to load an image to illustrate it better, but I haven't made enough post.

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• Export large amount of data from Oracle 10G to SQL Server 2005

  - by uniball

  Dear all, I need to export 100 million data rows (avg row length ~ 100 bytes) from Oracle 10G database table into SQL server (over WAN/VLAN with 6MBits/sec capacity) on a regular basis. So far, these are the options that I have tried and a quick summary. Has anyone tried this before? Are there other better options? Which option would be the best in terms of performance and reliability? The time taken has been calculated using tests on smaller amounts of data and then extrapolating it to estimate the time required. Using data import wizard on the SQL server or SSIS packages to import the data. It will take around 150 hours to complete the task. Using Oracle batch job to spool data into a comma-delimited flat-file. Then using SSIS package to FTP this file to the SQL server and then load directly from the flat-file. The issue here is the size of the flat-file which is expected to run in GBs. Although this option is drastically different, I am even considering the option of using Linked Server to query the Oracle data directly at run-time to avoid bringing in data. Performance is a big problem and I have limited control over the Oracle database in terms of creating table indexes. Regards, Uniball

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• Dynamic evaluation of a table column within an insert before trigger

  - by Tim Garver

  HI All, I have 3 tables, main, types and linked. main has an id column and 32 type columns. types has id, type linked has id, main_id, type_id I want to create an insert before trigger on the main table. It needs to compare its 32 type columns to the values in the types table if the main table column has an 'X' for its value and insert the main_id and types_id into the linked table. i have done a lot of searching, and it looks like a prepared statement would be the way to go, but i wanted to ask the experts. The issue, is i dont want to write 32 IF statements, and even if i did, i need to query the types table to get the ID for that type, seems like a huge waist of resources. Ideally i want to do this inside of my trigger: BEGIN DECLARE @types results_set -- (not sure if this is a valid type); -- (iam sure my loop syntax is all wrong here)... SET @types = (select * from types) for i=0;i<types.records;i++ { IF NEW.[i.type] = 'X' THEN insert into linked (main_id,type_id) values (new.ID, i.id); END IF; } END; Anyway, This is what i was hoping to do, maybe there is a way to dynamically set the field name inside of a results loop, but i cant find a good example of this. Thanks in advance Tim

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• MySql Check if NOW() falls within a weekday/time range

  - by Niall

  I have a table as follows: CREATE TABLE `zonetimes` ( `id` int(11) unsigned NOT NULL AUTO_INCREMENT, `zone_id` int(10) unsigned NOT NULL, `active_from_day` tinyint(1) unsigned NOT NULL DEFAULT '2', `active_to_day` tinyint(1) unsigned NOT NULL DEFAULT '2', `active_from` time NOT NULL, `active_to` time NOT NULL PRIMARY KEY (`id`) ) ENGINE=MyISAM ; So, a user could add a time entry starting on a particular day and time and ending on a particular day and time, eg: Between Monday 08:00 and Friday 18:00 or Between Thursday 15:00 and Tuesday 15:00 (Note the crossover at the end of the week). I need to query this data and determine if a zone is currently active (NOW(), DAYOFWEEK() etc)... This is turning out to be quite tricky. If I didn't have overlaps, eg: from 'Wednesday 8pm to Tuesday 4am' or from 'Thursday 4pm to Tuesday 4pm' this would be easy with BETWEEN. Also, need to allow a user to add for the entire week, eg: Monday 8am - Monday 8am (This should be easy enough, eg: where (active_from_day=active_to_day AND active_from=active_to) OR .. Any ideas? Note: I found a similar question here Timespan - Check for weekday and time of day in mysql but it didn't get an answer. One of the suggestions was to store each day as a separate row. I would much rather store one time span for multiple days though.

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• SharePoint webpart with button to auto-login to 3rd party website

  - by JCdowney

  I have been tasked with creating a SharePoint 2007 webpart that logs the user directly into our website (which uses forms authentication). Most likely the username and password will be same in the SharePoint account as in our website. Ideally we would like it to be fully integrated in that the webpart looks up the SP login & password, somehow encodes that using SHA1, MD5 or similar encryption, then passes that along to our login page on the query string. However given we have little experience with SharePoint, and that it's probably impossible to programmatically access the SP username/password from a webpart we realize this isn't very likely to be possible and if so would probably require a lot of development time. Another option would be to load a login form from the website within an iframe in the webpart, which would show the login & password first but store a "remember me" cookie after the first login, and on each subsequent load display just a button that logs them in directly using the cookie. Has anyone done something similar before? I'm in over my head, any guidance would be much appreciated! :)

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• Dynamically Run IQueryable Method

  - by Micah

  Hi! I'm trying to run the Count() function of a Linq statement in an overriden Gridview function. Basically, I want to be able to assign a linq query to a gridview, and on the OnDataBound(e) event in my new extended gridview have it retrieve the count, using the IQueryable. This is where I'm at so far: protected override void OnDataBound(EventArgs e) { IEnumerable _data = null; if (this.DataSource is IQueryable) { _data = (IQueryable)this.DataSource; } System.Type dataSourceType = _data.GetType(); System.Type dataItemType = typeof(object); if (dataSourceType.HasElementType) { dataItemType = dataSourceType.GetElementType(); } else if (dataSourceType.IsGenericType) { dataItemType = dataSourceType.GetGenericArguments()[0]; } else if (_data is IEnumerable) { IEnumerator dataEnumerator = _data.GetEnumerator(); if (dataEnumerator.MoveNext() && dataEnumerator.Current != null) { dataItemType = dataEnumerator.Current.GetType(); } } Object o = Activator.CreateInstance(dataItemType); object[] objArray = new object[] { o }; RowCount = (int)dataSourceType.GetMethod("Count").Invoke(_data, objArray); Any ideas? I'm really new with working with IQueryables and Linq so I may be way off. How can I get my _data to allow me to run the Count function?

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• SQLAlchemy Custom Type Which Contains Multiple Columns

  - by Kekoa

  I would like to represent a datatype as a single column in my model, but really the data will be stored in multiple columns in the database. I cannot find any good resources on how to do this in SQLAlchemy. I would like my model to look like this(this is a simplified example using geometry instead of my real problem which is harder to explain): class 3DLine(DeclarativeBase): start_point = Column(my.custom.3DPoint) end_point = Column(my.custom.3DPoint) This way I could assign an object with the (x, y, z) components of the point at once without setting them individually. If I had to separate each component, this could get ugly, especially if each class has several of these composite objects. I would combine the values into one encoded field except that I need to query each value separately at times. I was able to find out how to make custom types using a single column in the documentation. But there's no indication that I can map a single type to multiple columns. I suppose I could accomplish this by using a separate table, and each column would be a foreign key, but in my case I don't think it makes sense to have a one to one mapping for each point to a separate table, and this still does not give the ability to set the related values all at once.

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• Are there good reasons not to use an ORM?

  - by hangy

  During my apprenticeship, I have used NHibernate for some smaller projects which I mostly coded and designed on my own. Now, before starting some bigger project, the discussion arose how to design data access and whether or not to use an ORM layer. As I am still in my apprenticeship and still consider myself a beginner in enterprise programming, I did not really try to push in my opinion, which is that using an object relational mapper to the database can ease development quite a lot. The other coders in the development team are much more experienced than me, so I think I will just do what they say. :-) However, I do not completely understand two of the main reasons for not using NHibernate or a similar project: One can just build one’s own data access objects with SQL queries and copy those queries out of Microsoft SQL Server Management Studio. Debugging an ORM can be hard. So, of course I could just build my data access layer with a lot of SELECTs etc, but here I miss the advantage of automatic joins, lazy-loading proxy classes and a lower maintenance effort if a table gets a new column or a column gets renamed. (Updating numerous SELECT, INSERT and UPDATE queries vs. updating the mapping config and possibly refactoring the business classes and DTOs.) Also, using NHibernate you can run into unforeseen problems if you do not know the framework very well. That could be, for example, trusting the Table.hbm.xml where you set a string’s length to be automatically validated. However, I can also imagine similar bugs in a “simple” SqlConnection query based data access layer. Finally, are those arguments mentioned above really a good reason not to utilise an ORM for a non-trivial database based enterprise application? Are there probably other arguments they/I might have missed? (I should probably add that I think this is like the first “big” .NET/C# based application which will require teamwork. Good practices, which are seen as pretty normal on Stack Overflow, such as unit testing or continuous integration, are non-existing here up to now.)

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• ASP.NET server data persistence

  - by Wayne Werner

  Hi, I'm not really sure exactly how the question should be phrased, so please be patient if I ask the wrong thing. I'm writing an ASP.NET application using VB as the code behind language. I have a data access class that connects to the DB to run the query (parameterized, of course), and another class to perform the validation tasks - I access this class from my aspx page. What I would like is to be able to store the data server side and wait for the user to choose from a few options based on the validity of the data. But unless my understanding is completely off, having persistent data objects on the server will give problems when multiple users connect? My ultimate goal is that once the data has been validated the end user can't modify it. Currently I'm validating the data, but I still have to retrieve it from the web form AFTER the user says OK, which obviously leaves open the possibility of injecting bad data either accidentally (unlikely) or on purpose (also unlikely for the use, but I'd prefer not to take the chance). So am I completely off in my understanding? If so, can someone point me to a resource that provides some instructions on keeping persistent data on the server, or provide instruction? Thanks!

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• Using nHibernate to map two different data models to one entity model

  - by Dan

  I have two different data models that map to the same Car entity. I needed to create a second entity called ParkedCar, which is identical to Car (and therefore inherits from it) in order to stop nhibernate complaining that two mappings exists for the same entity. public class Car { protected Car() { IsParked = false; } public virtual int Id { get; set; } public bool IsParked { get; internal set; } } public class ParkedCar : Car { public ParkedCar() { IsParked = true; } //no additional properties to car, merely exists to support mapping and signify the car is parked } The only issue is that when I come to retrieve a Car from the database using the Criteria API like so: SessionProvider.OpenSession.Session.CreateCriteria<Car>() .Add(Restrictions.Eq("Id", 123)) .List<Car>(); The query brings back Car Entities that are from the ParkedCar data model. Its as if nhibernate defaults to the specialised entity. And the mappings are defiantly looking in the right place: <class name="Car" xmlns="urn:nhibernate-mapping-2.2" table="tblCar"> <class name="ParkedCar" xmlns="urn:nhibernate-mapping-2.2" table="tblParkedCar" > How do I stop this?

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