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  • ADO.NET DataTable/DataRow Thread Safety

    - by Allen E. Scharfenberg
    Introduction A user reported to me this morning that he was having an issue with inconsistent results (namely, column values sometimes coming out null when they should not be) of some parallel execution code that we provide as part of an internal framework. This code has worked fine in the past and has not been tampered with lately, but it got me to thinking about the following snippet: Code Sample lock (ResultTable) { newRow = ResultTable.NewRow(); } newRow["Key"] = currentKey; foreach (KeyValuePair<string, object> output in outputs) { object resultValue = output.Value; newRow[output.Name] = resultValue != null ? resultValue : DBNull.Value; } lock (ResultTable) { ResultTable.Rows.Add(newRow); } (No guarantees that that compiles, hand-edited to mask proprietery information.) Explanation We have this cascading type of locking code other places in our system, and it works fine, but this is the first instance of cascading locking code that I have come across that interacts with ADO .NET. As we all know, members of framework objects are usually not thread safe (which is the case in this situation), but the cascading locking should ensure that we are not reading and writing to ResultTable.Rows concurrently. We are safe, right? Hypothesis Well, the cascading lock code does not ensure that we are not reading from or writing to ResultTable.Rows at the same time that we are assigning values to columns in the new row. What if ADO .NET uses some kind of buffer for assigning column values that is not thread safe--even when different object types are involved (DataTable vs. DataRow)? Has anyone run into anything like this before? I thought I would ask here at StackOverflow before beating my head against this for hours on end :) Conclusion Well, the consensus appears to be that changing the cascading lock to a full lock has resolved the issue. That is not the result that I expected, but the full lock version has not produced the issue after many, many, many tests. The lesson: be wary of cascading locks used on APIs that you do not control. Who knows what may be going on under the covers!

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  • Is there a consolidated way of writing several prototype functions for a single object?

    - by Christopher Altman
    I have about eight prototype functions for the Date object. I would like to avoid repeating Date.prototype. Is there a consolidated way of writing several prototype functions for a single object? I tried this to no avail: Date.prototype = { getMonthText: function(date){ var month = this.getMonth(); if(month==12) month = 0; return ['JAN','FEB','MAR','APR','MAY','JUN','JUL','AUG','SEP','OCT','NOV','DEC'][month]; }, getDaysInMonth: function(date){ return 32 - new Date(this.getFullYear(), this.getMonth(), 32).getDate(); } };

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  • Silverlight 3 version compatibility

    - by Tom Allen
    We've noticed a compatibility issue with a Silverlight 3 app which runs fine with v3.0.40818, v3.0.50106 and v4.0.50401 but refuses to load in v3.0.40624. Instead it gives a message box saying a more recent version of Silverlight is required. Does anyone know what the changes were between 3.0.40624 and 3.0.40818 or why the app might not be compatible?

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  • How do you run your unit tests? Compiler flags? Static libraries?

    - by Christopher Gateley
    I'm just getting started with TDD and am curious as to what approaches others take to run their tests. For reference, I am using the google testing framework, but I believe the question is applicable to most other testing frameworks and to languages other than C/C++. My general approach so far has been to do either one of three things: Write the majority of the application in a static library, then create two executables. One executable is the application itself, while the other is the test runner with all of the tests. Both link to the static library. Embed the testing code directly into the application itself, and enable or disable the testing code using compiler flags. This is probably the best approach I've used so far, but clutters up the code a bit. Embed the testing code directly into the application itself, and, given certain command-line switches either run the application itself or run the tests embedded in the application. None of these solutions are particularly elegant... How do you do it?

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  • How to check if EditText has a value in Android / Java

    - by Allen Gingrich
    This should be simple, but I have tried if statements checking for null values and also ones checking the .length of it: EditText marketValLow = (EditText) findViewById(R.id.marketValLow); EditText marketValHigh = (EditText) findViewById(R.id.marketValHigh); if (marketValLow.getText().length() != 0 && marketValHigh.getText().length() != 0) { Intent intent = new Intent(); intent.setClass(v.getContext(), CurrentlyOwe.class); startActivity(intent); } else { Toast.makeText(CurrentMarketValue.this, "You need to enter a high AND low.", Toast.LENGTH_SHORT); } But it doesn't detect nothing was entered. Any ideas? Thanks!

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  • Connecting a PHP front-end to a back-end java service

    - by christopher-mccann
    I am currently using various back-end services and I want to use PHP to simply query these services and perform the final page construction. These services could be coded in any number of programming langauges such as Erlang, Java, Python etc. However I am unsure of the best way to actually interface the back-end services with the web app. Requests to these services would be both synchronous and asynchronous. Would I use something like SOAP or JSON-RPC?? Any help greatly appreciated.

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  • Need help with a LINQ ArgumentOutOfRangeException in C#

    - by Christopher Klein
    Hi there, Hoping this is a nice softball of a question for a friday but I have the following line of code: //System.ArgumentOutOfRangeException generated if there is no matching data currentAnswers = new CurrentAnswersCollection().Where("PARTICIPANT_ID", 10000).Load()[0]; CurrentAnswersCollection is a strongly-typed collection populated by a view going back to my database. The problem of course is that if there is not a corresponding PARTICIPANT_ID = 10000 I get the error message. Is there a better way to write this so that I wouldn't get the error message at all? I just dont know enough about LINQ syntax to know if I can test for the existance first? thanks.

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  • Switching to tabs to the right or left of the current tab in Notepad++

    - by Christopher Swiedler
    How can I switch to the document to the left or right of the current document in Notepad++? For example, if I have documents A, B, and C open, and I'm currently editing B, I would like a shortcut to be able to switch to A (Alt-LeftArrow or Ctrl-Pageup) or C (Alt-RightArrow or Ctrl-PageDown). Is this possible? All I've found is a way to switch to next or previous documents based on the "history" of when the document was last opened (Ctrl-Tab and Ctrl-Shift-Tab), which are useful, but not what I want.

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  • Why doesn't splicing an object from an array in Javascript return the array?

    - by Allen Gould
    I have an array of objects (say, a deck of cards): var deck = []; deck.push(new Card(suit, rank)); The following seems to work: var card = deck.pop(); var card = deck.shift(); (pulling from the "top" or "bottom" of the deck respectively) But if I want a card from the middle (say, if this was a hand of cards) var card = deck.splice(2,1); The object doesn't seem to get properly assigned to the variable (everything is undefined). Everything I look up says that splice should return the object that I'm removing - what am I missing?

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  • PHP REMOTE_ADDR and secure sessions

    - by Christopher McCann
    One of the ways I have used to make securer sessions in the past is to also record the clients IP address and user agent at the handshake. Each time the client moves a page and calls session_start() I also check that the IP address and user agent stored is still the same to prevent hiijacking. But if someone is connecting from say a company network then all the users will probably have the same external static IP address and they could also really easily be using the same user agent. Is there other metrics I can use which are local only to the physical machine? Thanks

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  • PHP not working under IIS on WIndows 7

    - by Jonathan Allen
    I recently installed PHP on IIS/Windows 7, but it isn't working. I am getting the entire source file in the browser window. FastCGI Settings shows c:\Program Files (x86)\PHP\php-cgi.exe Handler Mappings has Request Path: *.php Modue: FastCgiModule Executable: C:\Program Files (x86)\PHP\php-cgi.exe Request Restrictions: File or Folder, All verbs, Script Access

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  • EXCEL - Locking a Cell from User input whilst allowing a Linked combobox?

    - by Christopher Leach
    I have a Protected Worksheet which is a checklist with a series of checkpoints. Each row has Item and Description cells that are locked. Each row has several columns with its contents to be set by a ComboBox and a text input column. Both i have left unlocked. I have Locked the the Item and Description columns and left only the 'Select Unlocked Cells' checked via Sheet Protection. I have one ComboBox on the worksheet that moves around and adjusts its LinkedCell and its Content list using the worksheets SelectionChanged event. When the user selects a cell to bring up the drop down list, the user is able to type into the cell and the Drop Down Box disappears. What is the best way to keep the cell unlocked so it can be selectable(as 'Select Locked Cells" is unchecked) however stop the user from being able to type in the cell and to allow the cells contents to become modifiable only via the ComboBox?

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  • Cassandra instead of MySQL for social networking app

    - by Christopher McCann
    I am in the middle of building a new app which will have very similar features to Facebook and although obviously it wont ever have to deal with the likes of 400,000,000 million users it will still be used by a substantial user base and most of them will demand it run very very quickly. I have extensive experience with MySQL but a social app offers complexities which MySQL is not well suited too. I know Facebook, Twitter etc have moved towards Cassandra for a lot of their data but I am not sure how far to go with it. For example would you store such things as user data - username, passwords, addresses etc in Cassandra? Would you store e-mails, comments, status updates etc in Cassandra? I have also read alot that something like neo4j is much better for representing the friend relationships used by social apps as it is a graph database. I am only just starting down the NoSQL route so any guidance is greatly appreciated. Would anyone be able to advise me on this? I hope I am not being too general!

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  • Request a Windows Phone 7.5 Location

    - by Christopher Cabezudo Rodriguez
    I am trying to track 5 windows phone 7.5 for a experiment and I have try using an app (that I am developing for that experiment) but the app must be active and that's not possible for all readings, I was looking online and I find something similar that Microsoft has done with the find my phone service, https://www.windowsphone.com/en-US/find Anyone knows how can i call that service outside the website or any other way to accomplish this task i need GEO position every 15 min

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  • List of SQL Server errors that should be retried?

    - by Christopher
    Is there a concise list of SQL Server stored procedure errors that make sense to automatically retry? Obviously, retrying a "login failed" error doesn't make sense, but retrying "timeout" does. I'm thinking it might be easier to specify which errors to retry than to specify which errors not to retry. So, besides "timeout" errors, what other errors would be good candidates for automatic retrying? Thanks!

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  • (SQL) Selecting from a database based on multiple pairs of pairs

    - by Owen Allen
    The problem i've encountered is attempting to select rows from a database where 2 columns in that row align to specific pairs of data. IE selecting rows from data where id = 1 AND type = 'news'. Obviously, if it was 1 simple pair it would be easy, but the issue is we are selecting rows based on 100s of pair of data. I feel as if there must be some way to do this query without looping through the pairs and querying each individually. I'm hoping some SQL stackers can provide guidance. Here's a full code break down: Lets imagine that I have the following dataset where history_id is the primary key. I simplified the structure a bit regarding the dates for ease of reading. table: history history_id id type user_id date 1 1 news 1 5/1 2 1 news 1 5/1 3 1 photo 1 5/2 4 3 news 1 5/3 5 4 news 1 5/3 6 1 news 1 5/4 7 2 photo 1 5/4 8 2 photo 1 5/5 If the user wants to select rows from the database based on a date range we would take a subset of that data. SELECT history_id, id, type, user_id, date FROM history WHERE date BETWEEN '5/3' AND '5/5' Which returns the following dataset history_id id type user_id date 4 3 news 1 5/3 5 4 news 1 5/3 6 1 news 1 5/4 7 2 photo 1 5/4 8 2 photo 1 5/5 Now, using that subset of data I need to determine how many of those entries represent the first entry in the database for each type,id pairing. IE is row 4 the first time in the database that id: 3, type: news appears. So I use a with() min() query. In real code the two lists are programmatically generated from the result sets of our previous query, here I spelled them out for ease of reading. WITH previous AS ( SELECT history_id, id, type FROM history WHERE id IN (1,2,3,4) AND type IN ('news','photo') ) SELECT min(history_id) as history_id, id, type FROM previous GROUP BY id, type Which returns the following data set. history_id id type user_id date 1 1 news 1 5/1 2 1 news 1 5/1 3 1 photo 1 5/2 4 3 news 1 5/3 5 4 news 1 5/3 6 1 news 1 5/4 7 2 photo 1 5/4 8 2 photo 1 5/5 You'll notice it's the entire original dataset, because we are matching id and type individually in lists, rather than as a collective pairs. The result I desire is, but I can't figure out the SQL to get this result. history_id id type user_id date 1 1 news 1 5/1 4 3 news 1 5/3 5 4 news 1 5/3 7 2 photo 1 5/4 Obviously, I could go the route of looping through each pair and querying the database to determine it's first result, but that seems an inefficient solution. I figured one of the SQL gurus on this site might be able to spread some wisdom. In case I'm approaching this situation incorrectly, the gist of the whole routine is that the database stores all creations and edits in the same table. I need to track each users behavior and determine how many entries in the history table are edits or creations over a specific date range. Therefore I select all type:id pairs from the date range based on a user_id, and then for each pairing I determine if the user is responsible for the first that occurs in the database. If first, then creation else edit. Any assistance would be awesome.

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