sortexpression gridview order desc doesn't work
GridView sorting: SortDirection always Ascending
Derivation of $E=pc$ for a massless particle? In classical mechanics, massless particles don't exist because for $m=0$, $p=0$.  The relativistic relation between energy, mass and spatial momentum is: $E^2= (pc)^2 + (mc^2)^2$ . So it is said that setting $m=0$ in the first equation you get $E=pc$.  How could setting $m=0$ in that equation give you $E=pc$ whilst $p$ appears in the equation and we know $p=γmu$? If you set $m=0$ you will have indeterminacy due to "$γm$". It seems to me like we are doing a "trick" in order to get the $E=pc$. Perhaps there is another proof for this relation? Dodecagon Area Question The distance between two opposite vertices of the dodecagon is 2. Find the area of the dodecagon.  Is there any way to do this without trigonometry?  And could you include a proof also? :O Why didn't the basilisk bite in Chamber of Secrets destroy the Horcrux? Using the Limit definition to find the derivative of $e^x$ I was wondering how we could use the limit definition   $$ \lim_{h \rightarrow 0} \frac{f(x+h)-f(x)}{h}$$  to find the derivative of $e^x$, I get to a point where I do not know how to simplify the indeterminate $\frac{0}{0}$. Below is what I have already done  $$\begin{align} &amp;\lim_{h \rightarrow 0} \frac{f(x+h)-f(x)}{h} \\ &amp;\lim_{h \rightarrow 0} \frac{e^{x+h}-e^x}{h} \\ &amp;\lim_{h \rightarrow 0} \frac{e^x (e^h-1)}{h} \\ &amp;e^x \cdot \lim_{h \rightarrow 0} \frac{e^h-1}{h} \end{align}$$  Where can I go from here? Because, the $\lim$ portion reduces to indeterminate when $0$ is subbed into $h$. Request Web Page in c# spoofing the Host I need to create a request for a web page delivered to our web sites, but I need to be able to set the host header information too.  I have tried this using HttpWebRequest, but the Header information is read only (Or at least the Host part of it is).  I need to do this because we want to perform the initial request for a page before the user can.  We have 10 web server which are load balanced, so we need to request the file from each of the web servers.    I have tried the following:  HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://192.168.1.5/filename.htm"); request.Headers.Set("Host", "www.mywebsite.com"); WebResponse response = request.GetResponse();   Obviously this does not work, as I can't update the header, and I don't know if this is indeed the right way to do it. Are there perfect elastic collisions in Nature? Pretty much every application I use in full-screen (including Firefox, MacVim and the Terminal) have tabs on the top of the screen.  The problem is, when I move my mouse to reach the tabs I'll often accidentally touch the top of the screen, bringing in the OS menu OVER the tabs:    Is there any way to change this behavior? I'd prefer it if the menu bar would stay hidden when I'm using a full-screen app, even if my mouse does touch the top of the screen. Why is there a difference between ping "localhost" and ping "local IP address"? Using cmd and ping on Windows gave me the following results:   Pinging "localhost":       Pinging "192.168.0.10" (local IP address):     Aren't both situations exactly the same?   I mean, I'm pinging the same interface, the same machine and the same address. Why do I get such different results?  EDIT: Here is my ipconfig /all screen: iOS app 1.4.3, iOS 9.2.1  While viewing a post, the app somehow ended up in a state where it refuses to do much of anything.  What does work:   Swipe-scrolling vertically Jumping to the previous / next post using the up / down buttons    Everything else, though, has no effect:   Swipe-scrolling horizontally will not return to the previous view Tapping on a code block will not zoom to code-block view Tapping Delete button to delete a post will show a confirmation dialog, but saying yes will not cause deletion The Add Comment button brings up the text field, but I cannot type anything in it; I can only dismiss it None of the other buttons (Share, More, etc.) do anything Cannot view user profiles or revision history Tapping on links in a post or comment will not show a web page Tapping on a tag shows some visual feedback with a temporary color change, but doesn't do anything else   I still receive push notifications, but tapping on them doesn't take me anywhere. Why is part of my model not being rendered? How to delete file(s) in secure manner? Is there a way to make sure that a deleted file can not be recovered?   As you know, deleting a file by pressing shift-del or using trash doesn't mean that file is gone forever. It resides somewhere in the computer.  In day to day life, law enforcement or thieves use recovery programs to reveal our private data or something else.   They can recover all data that resides on hard disk, in RAM, and even USB.  To protect us from these people, what should one do? Which program should one use?  Note: I don't want an answer like first use a recovery program then erase that file with shred. With just one program, I want to erase all unused/deleted files on my computer. Is there a thumb-rule for designing neural-networks? I know that a neural-network architecture is mostly based on the problem itself and the types of input/output, but still - there's always a "square one" when starting to build one. So my question is - given a input dataset of MxN (M  is the number of records, N is the number of features) and a C possible output classes - is there a thumb-rule to how many layers/units should we start with? Geometrical representation of Contravariant and covariant vectors After cruising through a lot of material online, and answers over here, my understanding of contravariant and covariant vectors are, in a finite-dimensional vector space, suppose we have a vector, which is contravariant to its basis. However, using the metric tensor, we can map this vector to a one form in the dual space, which acts as a vector space for this example. This one form, or covactor, varies similarly to the basis in our original vector space. However, the covectors have a different basis, which is the dual basis, and are expanded in terms of those. Here's where my confusion arises : Many diagrams over the internet give a geometric picture of the scenario, by claiming that contravariant components of an 'arrow' are found by drawing parallel lines along the axes, and checking where they intersect. Co-variant components could be found by sketching the perpendicular lines on these axes. So, these materials are treating covariant and contravariant as different representations of the same arrow, while I'm inclined to believe they are completely different. However, if we let go of rigour, in exchange for a 'more' geometric understanding, I think we are allowed to do this. The diagrams are usually of the form :  However, even if we assume that contravariant and covariant are different representations of the same object, this particular diagram still seems wrong to me. Particularly the locations of $x_1,x_2$. In this diagram, they are located on the span of the original basis. Shouldn't covector components be located on the span of the dual basis ? This diagram suggests to me, that co-variant components have the same basis, as the contravariant ones. Shouldn't the diagram look more like this ?  This second diagram seems to fit the concept better according to me. This is because the dual vector must be 'contravariant' with respect to the 'dual basis'. This means, their components must be found out by sketching parallel lines along the span of the dual basis. These lines intersect the original axis at a right angle, which is to be expected, as dual bases are orthogonal to the original bases. Moreover, this second picture can also show in a much better way, how scaling up of the original basis, scales down the 'contravariant components' and the 'dual basis', which in turn scales up the 'covariant' components.This shows that the components of the dual vector are covariant to the original basis. This is something that is not readily visible in the first diagram. So, am I correct in assuming this second 'geometrical' representation is correct ? I know this doesn't make much sense, because as the mathematicians said, that vectors are completely different from one forms, and one forms should be represented using the number of hyperplanes intercepted by our arrow. However, I've seen most course material refer to it in this way, and frankly it is easier to visualize. However, most of this material used the first picture. Can anyone point out my mistakes, if any, and tell me if the first picture is correct, or the second one ? Or in this case 'less-flawed'. we are currently experiencing some issues with the ambiguity feature of apa for biblatex/biber (we use biber) in TexLive 2012.  What would be correct with the ambiguity feature:  Doe J., Peters M., Kramer N., Conan B. (2012) Doe J., Mayer M., Smith N., Walker J. (2012)  Citations in text (subsequent ones) - AS IS AND CORRECT Doe, Peters et al (2012) Doe, Mayer et al (2012)   But in case of different years, it shouldn't actually do this ...  Doe J., Peters M., Kramer N., Conan B. (2012) Doe J., Mayer M., Smith N., Walker J. (2009)  Citations in text (subsequent ones) - AS IS: Doe, Peters et al (2012) Doe, Mayer et al (2009)  Citations in text (subsequent ones) - HOW IT SHOULD BE: Doe et al (2012) Doe et al (2009)   Can anyone help here?  Thank you! Reputation widget crash I have an issue with crashing reputation widget when it's added to the home screen. When I add it for the first time, it says "Please login before using this widget" (even though the app itself is logged in already). So I open the app, go back to the home screen, add the widget again and it crashes (and it's not added to the home screen). When I'll try to add it again, it says "Please login before using this widget" again. And then it just repeats - "Please login...", execute the app, crash, "Please login...", etc.  Restart of the device didn't make any change.  I have found .  My set up:  Stack Exchange app version: 1.0.89 Android version: 5.0.1 Device: Samsung Galaxy S4 Prove that a set in $\mathbb R^3$ is not an algebraic set I want to prove that the set $\{(\cos(t),\sin(t),t)\in A^3(\mathbb R); t\in \mathbb R \}$ is not an algebraic set.   I already proved that the set $\{(\sin(t),t)\in A^2(\mathbb R);t\in \mathbb R \}$ is not algebraic but the method that I used doesn't seems to be general. Does "FN" stand for or mean anything? Windows 10 Anniversary Upgrade error 0xc1900101 - 0x30018 referring to SYSPREP Geometric intuition behind gradient, divergence and curl Reference Books on Cryptography