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• Fluent Nhibernate mapping related items

  - by Josh

  I am trying to relate 2 items. I have a table that is simply an Id field, and then 2 columns for the Item Id's to relate. I want it to be a 2 way relationship - that is, if the items appear twice in the table, I only want one relationship connection back. So, here's my item: public class Item { public virtual Guid ItemId {get; set;} public virtual string Name {get; set;} public virtual IList<Item> RelatedItems {get; set;} } The table for relating the items looks like this: CREATE TABLE RelatedItems ( RelatedItemId uniqueidentifier NOT NULL, ItemId uniqueidentifier NOT NULL, RelatedId uniqueidentifier NOT NULL, CONSTRAINT PK_RelatedItems PRIMARY KEY CLUSTERED (RelatedItemId) ) What is the best way to map this connection?

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• How to generate a private/public key pair to use for a Linux server on Windows Azure?

  - by MainMa

  Following Windows Azure documentation, I generated a pair of private/public keys on an Ubuntu machine using the exact comment as given: openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout myPrivateKey.key -out myCert.pem When I open the private key in puttygen, the following error is displayed: Couldn't load private key (unrecognised key type) The private key generated by openssl looks correct: -----BEGIN PRIVATE KEY----- MIIEvQIBADANBgkqhkiG6w0xAQEFAASCBKcwggSjAgEsAoIBAQC6OEZ5ULe6F6u2 Cybhqqfqqh2ao9sd2tpqB+HGIoMMHrmnD3YegRgZJIddTQaWKdwaKrYul21YNt5y ... P0RyfL9kDnX/XmIOM38FOoucGvO+Zozsbmgmvw6AUhE0sPhkZnlaodAU1OnfaWJz KpBxkXulBaCJnC8w29dGKng= -----END PRIVATE KEY----- Note that the comments to Azure documentation (the same link as above) report that the pair should be generated using OpenSSL for Windows instead of openssl on Linux. This doesn't help, since the same error appears for a private key generated by OpenSSL for Windows. What am I doing wrong?

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• iTerm2 vim cannot map alt key

  - by Eddy

  I'm having trouble trying to map the alt-key bindings on vim in iTerm2. I want to map shortcuts for switching between buffers like this: map <A-Right> <C-w>l map <A-Left> <C-w>h map <A-Down> <C-w>j map <A-Up> <C-w>k But I can't get it to work. I've tried everything, setting the option key as "Normal", "Meta" and "+Esc" in the profile settings. I've tried <M-Right> and <T-Right> but those don't work either. There are posts on superuser and stackoverflow but they use the old version of iTerm2 (v0.x). The only things I've managed to get working are <T-up> and <T-down>, or when I just use Macvim. I'm using iTerm2 v1.0.0.20120203, and Mac OS X 10.7.5 on a Macbook Pro.

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• [Linux] Bind/map Character to alt+[some key]?

  - by Paul

  OS: Ubuntu In programming and various terminal programs (Screen, Vim) the [, ], { and } tends to be used a lot. I'm using a Norwegian keyboard where these are placed such that I have to stretch my fingers a bit too long for whats comfortable. To make it easier I though I'd try to make alt+[some key] be one of these characters. Is there a way that I can bind, say alt+æ (Norwegian letter) to '{' system wide? Btw, is such thing called binding, mapping or something else? I'm getting a bit confused by the terms... :)

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• Mapping UrlEncoded POST Values in ASP.NET Web API

  - by Rick Strahl

  If there's one thing that's a bit unexpected in ASP.NET Web API, it's the limited support for mapping url encoded POST data values to simple parameters of ApiController methods. When I first looked at this I thought I was doing something wrong, because it seems mighty odd that you can bind query string values to parameters by name, but can't bind POST values to parameters in the same way. To demonstrate here's a simple example. If you have a Web API method like this:[HttpGet] public HttpResponseMessage Authenticate(string username, string password) { …} and then hit with a URL like this: http://localhost:88/samples/authenticate?Username=ricks&Password=sekrit it works just fine. The query string values are mapped to the username and password parameters of our API method. But if you now change the method to work with [HttpPost] instead like this:[HttpPost] public HttpResponseMessage Authenticate(string username, string password) { …} and hit it with a POST HTTP Request like this: POST http://localhost:88/samples/authenticate HTTP/1.1 Host: localhost:88 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Content-type: application/x-www-form-urlencoded Content-Length: 30 Username=ricks&Password=sekrit you'll find that while the request works, it doesn't actually receive the two string parameters. The username and password parameters are null and so the method is definitely going to fail. When I mentioned this over Twitter a few days ago I got a lot of responses back of why I'd want to do this in the first place - after all HTML Form submissions are the domain of MVC and not WebAPI which is a valid point. However, the more common use case is using POST Variables with AJAX calls. The following is quite common for passing simple values:$.post(url,{ Username: "Rick", Password: "sekrit" },function(result) {…}); but alas that doesn't work. How ASP.NET Web API handles Content Bodies Web API supports parsing content data in a variety of ways, but it does not deal with multiple posted content values. In effect you can only post a single content value to a Web API Action method. That one parameter can be very complex and you can bind it in a variety of ways, but ultimately you're tied to a single POST content value in your parameter definition. While it's possible to support multiple parameters on a POST/PUT operation, only one parameter can be mapped to the actual content - the rest have to be mapped to route values or the query string. Web API treats the whole request body as one big chunk of data that is sent to a Media Type Formatter that's responsible for de-serializing the content into whatever value the method requires. The restriction comes from async nature of Web API where the request data is read only once inside of the formatter that retrieves and deserializes it. Because it's read once, checking for content (like individual POST variables) first is not possible. However, Web API does provide a couple of ways to access the form POST data: Model Binding - object property mapping to bind POST values FormDataCollection - collection of POST keys/values ModelBinding POST Values - Binding POST data to Object Properties The recommended way to handle POST values in Web API is to use Model Binding, which maps individual urlencoded POST values to properties of a model object provided as the parameter. Model binding requires a single object as input to be bound to the POST data, with each POST key that matches a property name (including nested properties like Address.Street) being mapped and updated including automatic type conversion of simple types. This is a very nice feature - and a familiar one from MVC - that makes it very easy to have model objects mapped directly from inbound data. The obvious drawback with Model Binding is that you need a model for it to work: You have to provide a strongly typed object that can receive the data and this object has to map the inbound data. To rewrite the example above to use ModelBinding I have to create a class maps the properties that I need as parameters:public class LoginData { public string Username { get; set; } public string Password { get; set; } } and then accept the data like this in the API method:[HttpPost] public HttpResponseMessage Authenticate(LoginData login) { string username = login.Username; string password = login.Password; … } This works fine mapping the POST values to the properties of the login object. As a side benefit of this method definition, the method now also allows posting of JSON or XML to the same endpoint. If I change my request to send JSON like this: POST http://localhost:88/samples/authenticate HTTP/1.1 Host: localhost:88 Accept: application/jsonContent-type: application/json Content-Length: 40 {"Username":"ricks","Password":"sekrit"} it works as well and transparently, courtesy of the nice Content Negotiation features of Web API. There's nothing wrong with using Model binding and in fact it's a common practice to use (view) model object for inputs coming back from the client and mapping them into these models. But it can be  kind of a hassle if you have AJAX applications with a ton of backend hits, especially if many methods are very atomic and focused and don't effectively require a model or view. Not always do you have to pass structured data, but sometimes there are just a couple of simple response values that need to be sent back. If all you need is to pass a couple operational parameters, creating a view model object just for parameter purposes seems like overkill. Maybe you can use the query string instead (if that makes sense), but if you can't then you can often end up with a plethora of 'message objects' that serve no further  purpose than to make Model Binding work. Note that you can accept multiple parameters with ModelBinding so the following would still work:[HttpPost] public HttpResponseMessage Authenticate(LoginData login, string loginDomain) but only the object will be bound to POST data. As long as loginDomain comes from the querystring or route data this will work. Collecting POST values with FormDataCollection Another more dynamic approach to handle POST values is to collect POST data into a FormDataCollection. FormDataCollection is a very basic key/value collection (like FormCollection in MVC and Request.Form in ASP.NET in general) and then read the values out individually by querying each. [HttpPost] public HttpResponseMessage Authenticate(FormDataCollection form) { var username = form.Get("Username"); var password = form.Get("Password"); …} The downside to this approach is that it's not strongly typed, you have to handle type conversions on non-string parameters, and it gets a bit more complicated to test such as setup as you have to seed a FormDataCollection with data. On the other hand it's flexible and easy to use and especially with string parameters is easy to deal with. It's also dynamic, so if the client sends you a variety of combinations of values on which you make operating decisions, this is much easier to work with than a strongly typed object that would have to account for all possible values up front. The downside is that the code looks old school and isn't as self-documenting as a parameter list or object parameter would be. Nevertheless it's totally functionality and a viable choice for collecting POST values. What about [FromBody]? Web API also has a [FromBody] attribute that can be assigned to parameters. If you have multiple parameters on a Web API method signature you can use [FromBody] to specify which one will be parsed from the POST content. Unfortunately it's not terribly useful as it only returns content in raw format and requires a totally non-standard format ("=content") to specify your content. For more info in how FromBody works and several related issues to how POST data is mapped, you can check out Mike Stalls post: How WebAPI does Parameter Binding Not really sure where the Web API team thought [FromBody] would really be a good fit other than a down and dirty way to send a full string buffer. Extending Web API to make multiple POST Vars work? Don't think so Clearly there's no native support for multiple POST variables being mapped to parameters, which is a bit of a bummer. I know in my own work on one project my customer actually found this to be a real sticking point in their AJAX backend work, and we ended up not using Web API and using MVC JSON features instead. That's kind of sad because Web API is supposed to be the proper solution for AJAX backends. With all of ASP.NET Web API's extensibility you'd think there would be some way to build this functionality on our own, but after spending a bit of time digging and asking some of the experts from the team and Web API community I didn't hear anything that even suggests that this is possible. From what I could find I'd say it's not possible primarily because Web API's Routing engine does not account for the POST variable mapping. This means [HttpPost] methods with url encoded POST buffers are not mapped to the parameters of the endpoint, and so the routes would never even trigger a request that could be intercepted. Once the routing doesn't work there's not much that can be done. If somebody has an idea how this could be accomplished I would love to hear about it. Do we really need multi-value POST mapping? I think that that POST value mapping is a feature that one would expect of any API tool to have. If you look at common APIs out there like Flicker and Google Maps etc. they all work with POST data. POST data is very prominent much more so than JSON inputs and so supporting as many options that enable would seem to be crucial. All that aside, Web API does provide very nice features with Model Binding that allows you to capture many POST variables easily enough, and logistically this will let you build whatever you need with POST data of all shapes as long as you map objects. But having to have an object for every operation that receives a data input is going to take its toll in heavy AJAX applications, with a lot of types created that do nothing more than act as parameter containers. I also think that POST variable mapping is an expected behavior and Web APIs non-support will likely result in many, many questions like this one: How do I bind a simple POST value in ASP.NET WebAPI RC? with no clear answer to this question. I hope for V.next of WebAPI Microsoft will consider this a feature that's worth adding. Related Articles Passing multiple POST parameters to Web API Controller Methods Mike Stall's post: How Web API does Parameter Binding Where does ASP.NET Web API Fit?© Rick Strahl, West Wind Technologies, 2005-2012Posted in Web Api   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• Mapping between 4+1 architectural view model & UML

  - by Sadeq Dousti

  I'm a bit confused about how the 4+1 architectural view model maps to UML. Wikipedia gives the following mapping: Logical view: Class diagram, Communication diagram, Sequence diagram. Development view: Component diagram, Package diagram Process view: Activity diagram Physical view: Deployment diagram Scenarios: Use-case diagram The paper Role of UML Sequence Diagram Constructs in Object Lifecycle Concept gives the following mapping: Logical view (class diagram (CD), object diagram (OD), sequence diagram (SD), collaboration diagram (COD), state chart diagram (SCD), activity diagram (AD)) Development view (package diagram, component diagram), Process view (use case diagram, CD, OD, SD, COD, SCD, AD), Physical view (deployment diagram), and Use case view (use case diagram, OD, SD, COD, SCD, AD) which combines the four mentioned above. The web page UML 4+1 View Materials presents the following mapping: Finally, the white paper Applying 4+1 View Architecture with UML 2 gives yet another mapping: Logical view class diagrams, object diagrams, state charts, and composite structures Process view sequence diagrams, communication diagrams, activity diagrams, timing diagrams, interaction overview diagrams Development view component diagrams Physical view deployment diagram Use case view use case diagram, activity diagrams I'm sure further search will reveal other mappings as well. While various people usually have different perspectives, I don't see why this is the case here. Specially, each UML diagram describes the system from a particular aspect. So, for instance, why the "sequence diagram" is considered as describing the "logical view" of the system by one author, while another author considers it as describing the "process view"? Could you please help me clarify the confusion?

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• DB Designer creates compound primary key

  - by Jon Winstanley

  When adding relationships to a database model in DB Designer 4, a composite primary key is being created every time. So every foreign key I add, I get an extra key added to a composite primary key. I think I must have changed a setting as I don't remember it doing this in the past. Does anyone know how to turn off this feature as I prefer to use a single surrogate primary keys in my database tables?

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• RC2 key schedule

  - by calccrypto

  Can someone explain how the RC2 key schedule works (particularly the very beginning of it)? i know it uses little endian, but my implementation is not working for any key except "0000 0000 0000 0000" Test Vector Key = 88bc a90e 9087 5a Plaintext = 0000 0000 0000 0000 Ciphertext = 6ccf 4308 974c 267f im assuming that the first thing to do with the key would be to change it into bc88 0ea9 8790 5a and yes i know RC2 is not even used anymore, but i would still like to know

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• How can I permanently save a password-protected SSH key?

  - by pl1nk

  I am using Awesome Window Manager How can I permanently add private keys with password? Inspired by the answer here I have added the private keys in ~/.ssh/config Contents of ~/.ssh/config: IdentityFile 'private key full path' Permissions of ~/.ssh/config: 0700 But it doesn't work for me. If I manually add the key in every session, it works but I'm looking for a more elegant way (not in .bashrc)

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• Mixing inheritance mapping strategies in NHibernate

  - by MylesRip

  I have a rather large inheritance hierarchy in which some of the subclasses add very little and others add quite a bit. I don't want to map the entire hierarchy using either "table per class hierarchy" or "table per subclass" due to the size and complexity of the hierarchy. Ideally I'd like to mix mapping strategies such that portions of the hierarchy where the subclasses add very little are combined into a common table a la "table per class hierarchy" and subclasses that add a lot are broken out into a separate table. Using this approach, I would expect to have 2 or 3 tables with very little wasted space instead of either 1 table with lots of fields that don't apply to most of the objects, or 20+ tables, several of which would have only a couple of columns. In the NHibernate Reference Documentation version 2.1.0, I found section 8.1.4 "Mixing table per class hierarchy with table per subclass". This approach switches strategies partway down the hierarchy by using: ... <subclass ...> <join ...> <property ...> ... </join> </subclass> ... This is great in theory. In practice, though, I found that the schema was too restrictive in what was allowed inside the "join" element for me to be able to accomplish what I needed. Here is the related part of the schema definition: <xs:element name="join"> <xs:complexType> <xs:sequence> <xs:element ref="subselect" minOccurs="0" /> <xs:element ref="comment" minOccurs="0" /> <xs:element ref="key" /> <xs:choice minOccurs="0" maxOccurs="unbounded"> <xs:element ref="property" /> <xs:element ref="many-to-one" /> <xs:element ref="component" /> <xs:element ref="dynamic-component" /> <xs:element ref="any" /> <xs:element ref="map" /> <xs:element ref="set" /> <xs:element ref="list" /> <xs:element ref="bag" /> <xs:element ref="idbag" /> <xs:element ref="array" /> <xs:element ref="primitive-array" /> </xs:choice> <xs:element ref="sql-insert" minOccurs="0" /> <xs:element ref="sql-update" minOccurs="0" /> <xs:element ref="sql-delete" minOccurs="0" /> </xs:sequence> <xs:attribute name="table" use="required" type="xs:string" /> <xs:attribute name="schema" type="xs:string" /> <xs:attribute name="catalog" type="xs:string" /> <xs:attribute name="subselect" type="xs:string" /> <xs:attribute name="fetch" default="join"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:enumeration value="join" /> <xs:enumeration value="select" /> </xs:restriction> </xs:simpleType> </xs:attribute> <xs:attribute name="inverse" default="false" type="xs:boolean"> </xs:attribute> <xs:attribute name="optional" default="false" type="xs:boolean"> </xs:attribute> </xs:complexType> </xs:element> As you can see, this allows the use of "property" child elements or "component" child elements, but not both. It also doesn't allow for "subclass" child elements to continue the hierarchy below the point at which the strategy was changed. Is there a way to accomplish this?

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• Synergy 1.4.2 Linux server, OSX client, Media/Function key mapping issues

  - by at165dB

  I'm using an Apple bluetooth keybord to control my Linux synergy server. SSH tunneling, Mouse, Keyboard, and Copy&Paste all work. Linux sees all the media/app keys that are on top of the F# keys correctly. However if I press any of those keys while controlling my OSX client, nothing happens on the client. Running synergys with -d DEBUG1 I can see the following keycode info: Pressing the "dim monitor" key that also serves as F1 generates: new mask: 0x2000 event: KeyPress code=232, state=0x0010 new mask: 0x2000 If I press "fn" and the same key, I can see it sending what I'm assuming is an F1: event: KeyPress code=67, state=0x0010 onKeyDown id=61374 mask=0x2000 button=0x0043 send key down to "foo.cisco.com" id=61374, mask=0x2000, button=0x0043 new mask: 0x2000 event: KeyRelease code=67, state=0x0010 onKeyUp id=61374 mask=0x2000 button=0x0043 send key up to "foo.cisco.com" id=61374, mask=0x2000, button=0x0043 I'm guessing I need to tweak my synergy.conf so that the server sends keys that it currently isn't. I'm also not sure what I need to do to tweak the keys that it is sending, but are not working. Below are all the other keys I'm having issues with. Does anyone have any idea how I can enable their functionality? brighten monitor: new mask: 0x2000 event: KeyPress code=233, state=0x0010 new mask: 0x2000 expose: new mask: 0x2000 event: KeyPress code=128, state=0x0010 new mask: 0x2000 dashboard: new mask: 0x2000 event: KeyPress code=212, state=0x0010 new mask: 0x2000 dim keyboard: new mask: 0x2000 event: KeyPress code=237, state=0x0010 new mask: 0x2000 brighten keyboard: new mask: 0x2000 event: KeyPress code=238, state=0x0010 new mask: 0x2000 rewind: event: KeyPress code=173, state=0x0010 onKeyDown id=57521 mask=0x2000 button=0x00ad send key down to "foo.cisco.com" id=57521, mask=0x2000, button=0x00ad new mask: 0x2000 event: KeyRelease code=173, state=0x0010 onKeyUp id=57521 mask=0x2000 button=0x00ad send key up to "foo.cisco.com" id=57521, mask=0x2000, button=0x00ad play/pause: event: KeyPress code=172, state=0x0010 onKeyDown id=57523 mask=0x2000 button=0x00ac send key down to "foo.cisco.com" id=57523, mask=0x2000, button=0x00ac new mask: 0x2000 event: KeyRelease code=172, state=0x0010 onKeyUp id=57523 mask=0x2000 button=0x00ac send key up to "foo.cisco.com" id=57523, mask=0x2000, button=0x00ac fastforward: event: KeyPress code=171, state=0x0010 onKeyDown id=57520 mask=0x2000 button=0x00ab send key down to "foo.cisco.com" id=57520, mask=0x2000, button=0x00ab new mask: 0x2000 event: KeyRelease code=171, state=0x0010 onKeyUp id=57520 mask=0x2000 button=0x00ab send key up to "foo.cisco.com" id=57520, mask=0x2000, button=0x00ab mute: event: KeyPress code=121, state=0x0010 onKeyDown id=57517 mask=0x2000 button=0x0079 send key down to "foo.cisco.com" id=57517, mask=0x2000, button=0x0079 new mask: 0x2000 event: KeyRelease code=121, state=0x0010 onKeyUp id=57517 mask=0x2000 button=0x0079 send key up to "foo.cisco.com" id=57517, mask=0x2000, button=0x0079 volume down: onKeyDown id=57518 mask=0x2000 button=0x007a send key down to "foo.cisco.com" id=57518, mask=0x2000, button=0x007a new mask: 0x2000 event: KeyRelease code=122, state=0x0010 onKeyUp id=57518 mask=0x2000 button=0x007a send key up to "foo.cisco.com" id=57518, mask=0x2000, button=0x007a volume up: event: KeyPress code=123, state=0x0010 onKeyDown id=57519 mask=0x2000 button=0x007b send key down to "foo.cisco.com" id=57519, mask=0x2000, button=0x007b new mask: 0x2000 event: KeyRelease code=123, state=0x0010 onKeyUp id=57519 mask=0x2000 button=0x007b send key up to "foo.cisco.com" id=57519, mask=0x2000, button=0x007b eject: event: KeyPress code=169, state=0x0010 onKeyDown id=57345 mask=0x2000 button=0x00a9 send key down to "foo.cisco.com" id=57345, mask=0x2000, button=0x00a9 new mask: 0x2000 event: KeyRelease code=169, state=0x0010 onKeyUp id=57345 mask=0x2000 button=0x00a9 send key up to "foo.cisco.com" id=57345, mask=0x2000, button=0x00a9

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• nHibernate Mapping file

  - by bharat

  <property name="NetworkRunId" column="Network_Run_Id" /> <property name="StudyKey" column="Study_Key" insert="false" update="false" /> <property name="AnnualizationFactor" column="Annualization_Factor" /> <property name="CreateDate" column="Create_Date" /> <property name="ModifyDate" column="Modify_Date" /> <many-to-one name="StudyInfo" class="Study" lazy="false" cascade="save-update"> <column name="Study_Key" /> </many-to-one> <many-to-one name="MemberInfo" class="BusinessDataEntities.Domain.NetworkAdministration.VHAMemberCompany, BusinessDataEntities" lazy="false"> <column name="Member_ID" /> </many-to-one> <many-to-one name="NetworkRunStudyXrefInfo" class="BusinessDataEntities.Domain.NetworkAdministration.NetworkRunStudyXref, BusinessDataEntities" lazy="false"> <column name="Network_Run_Id" /> </many-to-one> <join table="[HCO_Spend_Network_Run_Study]"> <key column="HCO_Spend_Id" /> <property name="NetworkRunId" column="Network_Run_Id" insert="false" update="false"/> </join> issue with the Network run id not exist in the first table but i have a join that is having the Network_Run_Id as property how do i fix this

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• Intuitive "Take Screenshot" key mapping used by games?

  - by Hatoru Hansou

  I recently had a problem testing my game on Linux Ubuntu. The Print key is intercepted by the desktop environment and It never reaches the game. Rather than fighting this, I will simply use any other key or key combination to trigger the screen capture functionality. Now, using the PRINT key is very intuitive because people already expect this behavior. What other keys are a good idea to use to take screenshots? And if possible elaborate why, have other apps/games used that key?

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• Inheritance Mapping Strategies with Entity Framework Code First CTP5: Part 2 – Table per Type (TPT)

  - by mortezam

  In the previous blog post you saw that there are three different approaches to representing an inheritance hierarchy and I explained Table per Hierarchy (TPH) as the default mapping strategy in EF Code First. We argued that the disadvantages of TPH may be too serious for our design since it results in denormalized schemas that can become a major burden in the long run. In today’s blog post we are going to learn about Table per Type (TPT) as another inheritance mapping strategy and we'll see that TPT doesn’t expose us to this problem. Table per Type (TPT)Table per Type is about representing inheritance relationships as relational foreign key associations. Every class/subclass that declares persistent properties—including abstract classes—has its own table. The table for subclasses contains columns only for each noninherited property (each property declared by the subclass itself) along with a primary key that is also a foreign key of the base class table. This approach is shown in the following figure: For example, if an instance of the CreditCard subclass is made persistent, the values of properties declared by the BillingDetail base class are persisted to a new row of the BillingDetails table. Only the values of properties declared by the subclass (i.e. CreditCard) are persisted to a new row of the CreditCards table. The two rows are linked together by their shared primary key value. Later, the subclass instance may be retrieved from the database by joining the subclass table with the base class table. TPT Advantages The primary advantage of this strategy is that the SQL schema is normalized. In addition, schema evolution is straightforward (modifying the base class or adding a new subclass is just a matter of modify/add one table). Integrity constraint definition are also straightforward (note how CardType in CreditCards table is now a non-nullable column). Another much more important advantage is the ability to handle polymorphic associations (a polymorphic association is an association to a base class, hence to all classes in the hierarchy with dynamic resolution of the concrete class at runtime). A polymorphic association to a particular subclass may be represented as a foreign key referencing the table of that particular subclass. Implement TPT in EF Code First We can create a TPT mapping simply by placing Table attribute on the subclasses to specify the mapped table name (Table attribute is a new data annotation and has been added to System.ComponentModel.DataAnnotations namespace in CTP5): public abstract class BillingDetail {     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } } [Table("BankAccounts")] public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } } [Table("CreditCards")] public class CreditCard : BillingDetail {     public int CardType { get; set; }     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } } public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; } } If you prefer fluent API, then you can create a TPT mapping by using ToTable() method: protected override void OnModelCreating(ModelBuilder modelBuilder) {     modelBuilder.Entity<BankAccount>().ToTable("BankAccounts");     modelBuilder.Entity<CreditCard>().ToTable("CreditCards"); } Generated SQL For QueriesLet’s take an example of a simple non-polymorphic query that returns a list of all the BankAccounts: var query = from b in context.BillingDetails.OfType<BankAccount>() select b; Executing this query (by invoking ToList() method) results in the following SQL statements being sent to the database (on the bottom, you can also see the result of executing the generated query in SQL Server Management Studio): Now, let’s take an example of a very simple polymorphic query that requests all the BillingDetails which includes both BankAccount and CreditCard types: projects some properties out of the base class BillingDetail, without querying for anything from any of the subclasses: var query = from b in context.BillingDetails             select new { b.BillingDetailId, b.Number, b.Owner }; -- var query = from b in context.BillingDetails select b; This LINQ query seems even more simple than the previous one but the resulting SQL query is not as simple as you might expect: -- As you can see, EF Code First relies on an INNER JOIN to detect the existence (or absence) of rows in the subclass tables CreditCards and BankAccounts so it can determine the concrete subclass for a particular row of the BillingDetails table. Also the SQL CASE statements that you see in the beginning of the query is just to ensure columns that are irrelevant for a particular row have NULL values in the returning flattened table. (e.g. BankName for a row that represents a CreditCard type) TPT ConsiderationsEven though this mapping strategy is deceptively simple, the experience shows that performance can be unacceptable for complex class hierarchies because queries always require a join across many tables. In addition, this mapping strategy is more difficult to implement by hand— even ad-hoc reporting is more complex. This is an important consideration if you plan to use handwritten SQL in your application (For ad hoc reporting, database views provide a way to offset the complexity of the TPT strategy. A view may be used to transform the table-per-type model into the much simpler table-per-hierarchy model.) SummaryIn this post we learned about Table per Type as the second inheritance mapping in our series. So far, the strategies we’ve discussed require extra consideration with regard to the SQL schema (e.g. in TPT, foreign keys are needed). This situation changes with the Table per Concrete Type (TPC) that we will discuss in the next post. References ADO.NET team blog Java Persistence with Hibernate book a { text-decoration: none; } a:visited { color: Blue; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } p.MsoNormal { margin-top: 0in; margin-right: 0in; margin-bottom: 10.0pt; margin-left: 0in; line-height: 115%; font-size: 11.0pt; font-family: "Calibri" , "sans-serif"; }

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• Class Mapping Error: 'T' must be a non-abstract type with a public parameterless constructor

  - by Amit Ranjan

  Hi, While mapping class i am getting error 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. Below is my SqlReaderBase Class public abstract class SqlReaderBase<T> : ConnectionProvider { #region Abstract Methods protected abstract string commandText { get; } protected abstract CommandType commandType { get; } protected abstract Collection<IDataParameter> GetParameters(IDbCommand command); **protected abstract MapperBase<T> GetMapper();** #endregion #region Non Abstract Methods /// <summary> /// Method to Execute Select Queries for Retrieveing List of Result /// </summary> /// <returns></returns> public Collection<T> ExecuteReader() { //Collection of Type on which Template is applied Collection<T> collection = new Collection<T>(); // initializing connection using (IDbConnection connection = GetConnection()) { try { // creates command for sql operations IDbCommand command = connection.CreateCommand(); // assign connection to command command.Connection = connection; // assign query command.CommandText = commandText; //state what type of query is used, text, table or Sp command.CommandType = commandType; // retrieves parameter from IDataParameter Collection and assigns it to command object foreach (IDataParameter param in GetParameters(command)) command.Parameters.Add(param); // Establishes connection with database server connection.Open(); // Since it is designed for executing Select statements that will return a list of results // so we will call command's execute reader method that return a Forward Only reader with // list of results inside. using (IDataReader reader = command.ExecuteReader()) { try { // Call to Mapper Class of the template to map the data to its // respective fields MapperBase<T> mapper = GetMapper(); collection = mapper.MapAll(reader); } catch (Exception ex) // catch exception { throw ex; // log errr } finally { reader.Close(); reader.Dispose(); } } } catch (Exception ex) { throw ex; } finally { connection.Close(); connection.Dispose(); } } return collection; } #endregion } What I am trying to do is , I am executine some command and filling my class dynamically. The class is given below: namespace FooZo.Core { public class Restaurant { #region Private Member Variables private int _restaurantId = 0; private string _email = string.Empty; private string _website = string.Empty; private string _name = string.Empty; private string _address = string.Empty; private string _phone = string.Empty; private bool _hasMenu = false; private string _menuImagePath = string.Empty; private int _cuisine = 0; private bool _hasBar = false; private bool _hasHomeDelivery = false; private bool _hasDineIn = false; private int _type = 0; private string _restaurantImagePath = string.Empty; private string _serviceAvailableTill = string.Empty; private string _serviceAvailableFrom = string.Empty; public string Name { get { return _name; } set { _name = value; } } public string Address { get { return _address; } set { _address = value; } } public int RestaurantId { get { return _restaurantId; } set { _restaurantId = value; } } public string Website { get { return _website; } set { _website = value; } } public string Email { get { return _email; } set { _email = value; } } public string Phone { get { return _phone; } set { _phone = value; } } public bool HasMenu { get { return _hasMenu; } set { _hasMenu = value; } } public string MenuImagePath { get { return _menuImagePath; } set { _menuImagePath = value; } } public string RestaurantImagePath { get { return _restaurantImagePath; } set { _restaurantImagePath = value; } } public int Type { get { return _type; } set { _type = value; } } public int Cuisine { get { return _cuisine; } set { _cuisine = value; } } public bool HasBar { get { return _hasBar; } set { _hasBar = value; } } public bool HasHomeDelivery { get { return _hasHomeDelivery; } set { _hasHomeDelivery = value; } } public bool HasDineIn { get { return _hasDineIn; } set { _hasDineIn = value; } } public string ServiceAvailableFrom { get { return _serviceAvailableFrom; } set { _serviceAvailableFrom = value; } } public string ServiceAvailableTill { get { return _serviceAvailableTill; } set { _serviceAvailableTill = value; } } #endregion public Restaurant() { } } } For filling my class properties dynamically i have another class called MapperBase Class with following methods: public abstract class MapperBase<T> where T : new() { protected T Map(IDataRecord record) { T instance = new T(); string fieldName; PropertyInfo[] properties = typeof(T).GetProperties(); for (int i = 0; i < record.FieldCount; i++) { fieldName = record.GetName(i); foreach (PropertyInfo property in properties) { if (property.Name == fieldName) { property.SetValue(instance, record[i], null); } } } return instance; } public Collection<T> MapAll(IDataReader reader) { Collection<T> collection = new Collection<T>(); while (reader.Read()) { collection.Add(Map(reader)); } return collection; } } There is another class which inherits the SqlreaderBaseClass called DefaultSearch. Code is below public class DefaultSearch: SqlReaderBase<Restaurant> { protected override string commandText { get { return "Select Name from vw_Restaurants"; } } protected override CommandType commandType { get { return CommandType.Text; } } protected override Collection<IDataParameter> GetParameters(IDbCommand command) { Collection<IDataParameter> parameters = new Collection<IDataParameter>(); parameters.Clear(); return parameters; } protected override MapperBase<Restaurant> GetMapper() { MapperBase<Restaurant> mapper = new RMapper(); return mapper; } } But whenever I tried to build , I am getting error 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. Even T here is Restaurant has a Parameterless Public constructor.

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• sudo apt-key adv --keyserver keyserver.ubuntu.com --recv 7F0CEB10 command returns error

  - by nyamka

  I'm trying to install Mongodb on Ubuntu 12 but when I run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv 7F0CEB10 This returned the error below: keyserver.ubuntu.com host not found gpgkeys: HTTP fetch error 7: couldn't connect: no such file or directory gpg:no valid openPGP data found gpg: Total number processes :0 I turned off Firewall on Iptables, but it don't work. Is there any idea?

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• Linux 'compose' key sequence extensions

  - by o_O Tync

  Compose key is a great way way to write all these ©–®—… stuff. It's really MUCH more handy than the windows "alt+0169" method. Is there a way to define additional sequences? E.g. I'd like to have "Compose+--" result in "?"

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• ssh authentication with public-private key pair

  - by Rui Gonçalves

  Hi! I'm wonder if is possible to authenticate the same user with different public-private keys pairs on the same remote host. For all production servers, the public-private key pair has been generated for the same user and then exported to the backup server for allowing ssh authentication without human intervention. However, I'm having problems on some production servers, once the password prompt is always displayed. Thanks in advance for the help, Best regards!

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• Signing a public key

  - by Gatura

  Am not sure where this is the right place to ask this Someone has asked me to sign their public key, how do i do that?

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• windows product key

  - by Chris

  Hi, I received from my distributer a wrong OEM version of a windows7, I dont have time to send it back and wait for an other. Can I use the UK product key with a dutch dvd? (the one I used myself)

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• Can't do SSH public key under cryptographed home [migrated]

  - by lucasvscn

  Sorry if I post this in the wrong place. I've readed this topic, but I not able to comment on someones answer, so I started a new topic. I can't do ssh public key login to my server and I think this issue is related to the fact my home is using cryptography which set the permissions to 700 on /home/MY-USER I've tried another workstation and everything works fine. I would be glad if someone help me to get out this without revert the cryptography.

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• SQL Server add primary key

  - by Paul

  I have a table that needs to be given a new primary key, as my predecesor used a varchar(8) row as the primary key, and we are having problems with it now. I know how to add the primary key, but am not sure of the correct way to add this new primary key to other tables that have the foreign key. Here is what I have: users table: old_user_id varchar(8) ... ... new_user_id int(11) orders table: order_id int(11) ... ... old_user_fk varchar(8) new_user_fk int(11) I need to get the same results whether I join the tables on users.old_user_id=orders.old_user_fk or users.new_user_id=orders.new_user_fk. Any help is appreciated.

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• one primary key column foreign key to 2 other table columns.How to resolve data entry issue.

  - by Rohit

  I have a requirement according to which I have to create a central Login system.We have 2 things Corporate and Brand each represented by tables "Corporate" and "Brand". When a corporate gets registered,corporateID is given,When a user under that corporate gets registered there is a table corporateuser in which corporateID is a foreign key and CorporateUserID is a primary key.Similarly in the case of a brand. So we have CorporateUserId and BrandUserID. Now i have a table called RegisteredUsers in which i want to have corporate as well as brand users.UserID is a primary key in this table which is a foreign key to both corporateuser as well as Branduser. now when i enter a corporateuser,I do an entry to corporateuser as well as RegisteredUsers.When i enter CorporateUserID in userID for RegisteredUsers.It gives foreign key violation error. I fully understand this error.How can i achieve this.This requirement is very rigid.Please tell a workaround

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• PHP/MYSQL Trouble Selecting by Primary Key

  - by djs22

  Hi all, So I have a primary key column called key. I'm trying to select the row with key = 1 via this code: $query ="SELECT * FROM Bowlers WHERE key = '1'"; $result = mysql_query($query) or die(mysql_error()); For some reason, I'm getting this result: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'key = '1'' at line 1 The mysql statement works for using other keys, ie WHERE name = 'djs22'. Any ideas?

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• "Host key verification failed" error when transfering files using SCP command

  - by rvsi

  When I am trying to transfer files using SCP command I'm getting this error (Removed my IP and RSA key): @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY! Someone could be eavesdropping on you right now (man-in-the-middle attack)! It is also possible that the RSA host key has just been changed. The fingerprint for the RSA key sent by the remote host is ------------------------(RSA key) Please contact your system administrator. Add correct host key in /home/users/myaccount/.ssh/known_hosts to get rid of this message. Offending key in /home/users/myaccount/.ssh/known_hosts:4 RSA host key for 'my IP' has changed and you have requested strict checking. Host key verification failed. lost connection I am using newly installed Ubuntu 12.04 and I can connect to this server using ssh. Any help?

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