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  • Can you get a Func<T> (or similar) from a MethodInfo object?

    - by Dan Tao
    I realize that, generally speaking, there are performance implications of using reflection. (I myself am not a fan of reflection at all, actually; this is a purely academic question.) Suppose there exists some class that looks like this: public class MyClass { public string GetName() { return "My Name"; } } Bear with me here. I know that if I have an instance of MyClass called x, I can call x.GetName(). Furthermore, I could set a Func<string> variable to x.GetName. Now here's my question. Let's say I don't know the above class is called MyClass; I've got some object, x, but I have no idea what it is. I could check to see if that object has a GetName method by doing this: MethodInfo getName = x.GetType().GetMethod("GetName"); Suppose getName is not null. Then couldn't I furthermore check if getName.ReturnType == typeof(string) and getName.GetParameters().Length == 0, and at this point, wouldn't I be quite certain that the method represented by my getName object could definitely be cast to a Func<string>, somehow? I realize there's a MethodInfo.Invoke, and I also realize I could always create a Func<string> like: Func<string> getNameFunc = () => getName.Invoke(x, null); I guess what I'm asking is if there's any way to go from a MethodInfo object to the actual method it represents, incurring the performance cost of reflection in the process, but after that point being able to call the method directly (via, e.g., a Func<string> or something similar) without a performance penalty. What I'm envisioning might look something like this: // obviously this would throw an exception if GetActualInstanceMethod returned // something that couldn't be cast to a Func<string> Func<string> getNameFunc = (Func<string>)getName.GetActualInstanceMethod(x); (I realize that doesn't exist; I'm wondering if there's anything like it.) If what I'm asking doesn't make sense, or if I'm being unclear, I'll be happy to attempt to clarify.

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  • undefined method `code' for nil:NilClass message with rails and a legacy database

    - by Jude Osborn
    I'm setting up a very simple rails 3 application to view data in a legacy MySQL database. The legacy database is mostly rails ORM compatible, except that foreign key fields are pluralized. For example, my "orders" table has a foreign key field to the "companies" table called "companies_id" (rather than "company_id"). So naturally I'm having to use the ":foreign_key" attribute of "belongs_to" to set the field name manually. I haven't used rails in a few years, but I'm pretty sure I'm doing everything right, yet I get the following error when trying to access "order.currency.code": undefined method `code' for nil:NilClass This is a very simple application so far. The only thing I've done is generate the application and a bunch of scaffolds for each of the legacy database tables. Then I've gone into some of the models to make adjustments to accommodate the above mentioned difference in database naming conventions, and added some fields to the views. That's it. No funny business. So my database tables look like this (relevant fields only): orders ------ id description invoice_number currencies_id currencies ---------- id code description My Order model looks like this: class Order < ActiveRecord::Base belongs_to :currency, :foreign_key=>'currencies_id' end My Currency model looks like this: class Currency < ActiveRecord::Base has_many :orders end The relevant view snippet looks like this: <% @orders.each do |order| %> <tr> <td><%= order.description %></td> <td><%= order.invoice_number %></td> <td><%= order.currency.code %></td> </tr> <% end %> I'm completely out of ideas. Any suggestions?

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  • Rspec > testing database views

    - by Sean McCleary
    How can database views be tested in Rspec? Every scenario is wrapped in a transaction and the data does not look like it is being persisted to the database (MySQL in my case). My view returns with an empty result set because none of the records are being persisted in the transaction. I am validating that the records are not being stored by setting a debug point in my spec and checking my data with a database client while the spec is being debugged. The only way I can think to have my view work would be if I could commit the transaction before the end of the scenario and then clear the database after the scenario is complete. Does anyone know how to accomplish this or is there a better way? Thanks

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  • fastest c++ file compression library available?

    - by Fabien Hure
    I have a need to find the best library to compress in memory data. I am currently using zlib but I am wondering if there is a better compression library; better in terms of performance and memory footprint. It should be able to handle multiple files in the same archive. I am looking for a C/C++ library. Performance is the key factor. The files that are being compressed are small to large XML files.

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  • jQuery querying the database

    - by mazhar kaunain baig
    The thing is that there are number of items in the HTML select list. I want to click on any of the items, then query the database on the id of that item, retrieve the value and then display that in the textbox. How would I query the database? I would really appreciate that if someone provides a code sample for querying the database.

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  • android database encryption

    - by user121196
    android uses sqlite database to store data, I need to encrypt the sqlite database, how can this be done? I understand that application data is private. However I need to explictly encrypt the sqlite database that my app is using.

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  • Are the ususal database performance-tuning tips invalide for a third-party app like Drupal

    - by Paul Strugger
    When you have a slow database app, the first suggestions that people make is to: Track the slow queries Add appropriate indexes In the case you are building your own application this is very logical, but when you use a CMS like Drupal, that are people have developed and tuned, is this approach valid? I mean, aren't Drupal tables already fine-tuned for performance? Even if I try to see which queries are the slow ones, what could I do about it? Re-write Drupal core?!?

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  • Storing large json strings to database + hash

    - by Guy
    I need to store quiete large JSON data strings to the database. I am using gzip to compress the string and therefore BLOB MySQL data type to store it. However, only 5% of all the requests contain unique data and only unique data ought to be stored to the database. My approach is as follows. array_multisort data (array [a, b, c] is virtually the same as [a, c, b]). json_encode data (json_encode is faster than serialize; we need string array representation for the step 3). sha1 data (slower than md5, though less possible the collisions). Check if the hash exists in the database. 5.1 yes – do not insert the data. 5.2. no – gzip the data and store it along the hash. Is there anything about this (apart from storing JSON data to the database in the first place) that sounds fishy or should be done a different way? p.s. We are talking about a database with roughly 1kk unique records being created every month.

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  • Configure WCF Service Behavior using database

    - by Achhar
    We use database to centralize our configuration. As part of it, I want to store the standard service behaviors configuration like expose service metatdata, service debug, service throttling for a service inside database rather than in web/app.config. I was planing to store the configuration for a behavior in database as XML. For e.g. <serviceDebug includeExceptionDetailsinFault=true / What I am struggling with is once I read this XML from database how do I create ServiceDebugBehavior instance from it and apply it to my service host? I have tried using XML Serializer but didn't had success. Any thoughts on how this could be achieved or any alternate solutions?

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  • function to profile / performance test PHP functions?

    - by Haroldo
    I'm not experiencing any performance issues, however I'd like to take a look at what takes how long and how much memory cpu it uses etc. I'd like to get a firsthand understanding of which things can be bottle necks etc and improve any code i might reuse or build upon... (perfectionist) I'm looking to create a litte function that i can call at the begining and end of each function that records: execution time memory used cpu demand any ideas?

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  • C# Dictionary Performance

    - by derek
    I am using a Dictionary to store data, and will be caching it. I would like to avoid server memory issues, and have good performance by limiting the size of the Dictionary<, either in size or number of entries. What is the best method of doing this? Is there another class I should be considering other than a Dictionary?

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  • Query MS Access database in VB 2008

    - by Logan
    Hi, I added an Access database as a Data Source in VB 2008. I want to query this database and use the information in various ways throughout the program. For example, there is an Employee table with first/last names of employees. I have a combobox on my form that I want to display all of the employees. So I want to query the database for all the rows in the Employee table, and add them to the combobox as I go. I am familiar with SQL Syntax, so I am not asking how to write the query itself, but rather how to fetch rows in VB code (mimicking php's mysql_fetch_assoc and mysql_connect essentially) Thanks! Edit: Also, I want to know if I can query a DB if I don't add it as a data source (if I know the path name of the database)

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  • Why would SQL be very slow when doing updates?

    - by ooo
    Suddenly doing updates into a few tables have gotten 10 times slower than they used to be. What are some good recommendations to determine root cause and optimization? Could it be that indexing certain columns are causing updates to be slow? Any other recommendations? I guess more important than guesses would be help on the process of identifying the root cause or metrics around performance. Is there anything in Fluent NHibernate that you can use to help identify the root cause of performance issues?

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  • A nuts and bolts reference to C# performance and memory use

    - by phil
    I wonder if anyone could point me in the direction where I can read about the nuts and bolts of C#. What I'm interested in learning are method call costs, what it costs to create objects and such. My aim of learning this is to get a better understanding of how increase the performance of an application and get a better understanding of how the C# language works. The reference should preferable be a book, a book that I can read cover to cover.

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  • Migrating an Access Database into SharePoint 2007.

    - by Mike T
    To my surprise and delight I read that an adminsitrator can import (nearly directly) an Access 2007 database into a sharepoint site. Automagically, the database in transformed into lists and views with some table lookup thrown in for good measure. With Access 2007 installed on the client machine, even the forms and what not can still be reused. To me... this sounds to good to be true. Has anyone actually dones this? With all this good news, where is the bad stuff and pitfalls to this. Depending on the size of the database, wouldn't this some how "gum up the works" in the SharPoint database? Sources: http://madhurahuja.blogspot.com/2007/01/adding-data-to-sharepoint-l-ists-in.html http://social.technet.microsoft.com/Forums/en-US/sharepointadmin/thread/17745835-a861-4984-9f44-7291fdae7d07

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  • Is it worth migrating to NHibernate 2.x from NHibernate 1.2?

    - by Amitabh
    We are using nHibernate 1.2 in a system which is not performing good. Will there be some performance improvement if we migrate to latest version of nHibernate? Overall is it a good idea to migrate to the latest version of nHibernate? EDIT: I want to use following features to improve performance. 1. Second level cache. 2. Joined Table. 3. MultiQuery to batch queries.

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  • C#.Net window application EXE and SQL SERVER 2000 Database at Client Machine

    - by user1397931
    Friends I have install a .net window application exe at client machine and its database in sql server 2000. For Exe I install .net framework and other support software and for DB i install sql server 2000 and Create Database over there and connect it. Working Properly But now client change Xp to window7. I search for installation of SQL Server 2000 , but its not working over there. So what i did, i send the MDF file of database with exe application and make connection string and its also working. Now i change something in DB , and trying to update .mdf file but its not reflecting the new one mdf its getting the old one. i am Stuck...... am i did any wrong ? because its difficult for me to fix. OR i want to know what is the efficient way of use of SQL Server 2000 database on window7 or any else solution is there? Please help me...

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  • jquery quering the database

    - by mazhar
    the thing is that there are number of items in the html select list,what i want to do is to click on any of the item, then query the database on the id of that item. retrieve the value and then display that in the textbox, how would i query the database? I would really appreciate that if someone provides the code sample for querying the database

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  • How to remove MySQL database?

    - by Masi
    You may notice from my last question that a problem caused some more problems here. My database is now unusable partly due to my interest to break things and my inability to look at error messages. I know that I should not reuse primary keys, but I would like to use them again after the removal of the database that I deteriorated. So How can you correctly remove MySQL database?

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