I did not find the TryParse method for the Guid.  I’m wondering how others handle converting a guid in string format into a guid type.  Guid Id; try {     Id = new Guid(Request.QueryString["id"]); } catch {     Id = Guid.Empty; }
I want to try to convert a string to a Guid, but I don't want to rely on catching exceptions (   for performance reasons - exceptions are expensive for usability reasons - the debugger pops up  for design reasons - the expected is not exceptional   In other words the code:  public static Boolean TryStrToGuid(String s, out Guid value) {     try     {         value = new Guid(s);         return true;     }     catch (FormatException)     {         value = Guid.Empty;         return false;     } }   is not suitable.  I would try using RegEx, but since the guid can be parenthesis wrapped, brace wrapped, none wrapped, makes it hard.   Additionally, I thought certain Guid values are invalid(?)    Update 1   had a good idea to catch only FormatException, rather than all. Changed the question's code sample to include suggestion.    Update 2  Why worry about thrown exceptions? Am I really expecting invalid GUIDs all that often?   The answer is yes. That is why I am using TryStrToGuid - I am expecting bad data.  Example 1 . I might be parsing folder names, checking to see if the text after the final . is a GUID.  c:\Program Files c:\Program Files.old c:\Users c:\Users.old c:\UserManager.{CE7F5AA5-6832-43FE-BAE1-80D14CD8F666} c:\Windows c:\Windows.old   Example 2 I might be running a heavily used web-server wants to check the validity of some posted back data. I don't want invalid data tying up resources 2-3 orders of magnitude higher than it needs to be.  Example 3 I might be parsing a search expression entered by a user.     If they enter GUID's I want to process them specially (such as specifically searching for that object, or highlight and format that specific search term in the response text.)    Update 3 - Performance benchmarks  Test converting 10,000 good Guids, and 10,000 bad Guids.  Catch FormatException:    10,000 good:     63,668 ticks    10,000 bad:   6,435,609 ticks  Regex Pre-Screen with try-catch:    10,000 good:    637,633 ticks    10,000 bad:     717,894 ticks  COM Interop CLSIDFromString    10,000 good:    126,120 ticks    10,000 bad:      23,134 ticks   p.s. I shouldn't have to justify a question.
Inverse metric in linearised gravity From what I've read, in the framework of linearised gravity, one perturbs the metric around a Minkowski background, $\eta_{\mu\nu}$, such that  $$g_{\mu\nu}(x)=\eta_{\mu\nu}+h_{\mu\nu}(x)\tag{1}$$  where $h_{\mu\nu}(x)$ is a small perturbation, i.e. $$\big\lvert h_{\mu\nu}\big\rvert&lt;&lt;1.\tag{2}$$  The inverse metric is then found by assuming the following ansatz:  $$g^{\mu\nu}(x)=\eta^{\mu\nu}+\tilde{h}^{\mu\nu}\tag{3}$$  where $\tilde{h}^{\mu\nu}$ is also small (i.e. $\big\lvert \tilde{h}_{\mu\nu}\big\rvert&lt;&lt;1$).   Using this, it is easy to find that  $$g^{\mu\nu}(x)=\eta^{\mu\nu}-h^{\mu\nu} \tag{4}$$  to first order.   My question is, what is the justification for this ansatz? Is it simply that one expects the inverse metric to have a similar form to the metric in order to satisfy $$g^{\mu\alpha}g_{\alpha\nu}=\delta^{\mu}_{\;\nu}~?\tag{5}$$ With 5 images I have to create a video of 60 seconds in ffmpeg, each image has to display for 15 seconds. after  15 seconds, first image has to fade out and 2nd image has to fade in, after that 2nd image has to fade out, 3rd image has to fade in..etc. Please guide me how can I achieve this using ffmpeg commands. Probability question of hats Signed to unsigned conversion in C - is it always safe? Electron shells in atoms: What causes them to exist as they do? I have seen similar posts, but I haven't seen what seems to be a clear and direct answer.  Why do only a certain number of electrons occupy each shell? Why are the shells arranged in certain distances from the nucleus? Why don't electrons just collapse into the nucleus or fly away?  It seems there are lots of equations and theories that describe HOW electrons behave (pauli exclusion principle), predictions about WHERE they may be located (Schrödinger equation, uncertainty principle), etc. But hard to find the WHY and/or causality behind these descriptive properties.  What is it about the nucleus and the electrons that causes them to attract/repel in the form of these shells at regular intervals and numbers of electrons per shell?  Please be patient with me, new to this forum and just an amateur fan of physics. Analogue of spherical coordinates in $n$-dimensions What's the analogue to spherical coordinates in $n$-dimensions? For example, for $n=2$ the analogue are polar coordinates $r,\theta$, which are related to the Cartesian coordinates $x_1,x_2$ by  $$x_1=r \cos  \theta$$ $$x_2=r \sin  \theta$$  For $n=3$, the analogue would be the ordinary spherical coordinates $r,\theta ,\varphi$, related to the Cartesian coordinates $x_1,x_2,x_3$ by  $$x_1=r \sin  \theta  \cos  \varphi$$ $$x_2=r \sin  \theta  \sin  \varphi$$ $$x_3=r \cos  \theta$$  So these are my questions: Is there an analogue, or several, to spherical coordinates in $n$-dimensions for $n&gt;3$? If there are such analogues, what are they and how are they related to the Cartesian coordinates? Thanks. Is there a prime which is the form of $10^n + 1$ except $2, 11, 101$? Is there a prime which is the form of $10^n + 1$ except $2, 11, 101$?  I confirm there isn't such prime for $n &lt; 64$. color glitches and weird texture in render When I look in my preview render everything looks fine (for not having finished lighting) but when i actually render it the color of my doughnut icing glitches and the texture of the table doesn't appear. Except when we use right to denote direction, what is the difference between these two terms?  Also, which one is the preferred construction between these two     Am I right?   or     Am I correct? I am using the below script to move two days back when script runs at starting two days of the year and also check first and second days of every month and move two days back. if [$month=&quot;01&quot;] &amp;&amp; [$day=&quot;01&quot;]; then         date=&quot;$last_month/$yes_day/$last_year&quot;         fulldate=&quot;$last_month/$yes_day/$last_year&quot; else         if [$month=&quot;01&quot;] &amp;&amp; [$day=&quot;02&quot;]; then                 date=&quot;$last_month/$yes_day/$last_year&quot;                 fulldate=&quot;$last_month/$yes_day/$last_year&quot;         else                 if [ $day = &quot;01&quot; ]; then                         date=&quot;$last_month/$yes_day/$year&quot;                         fulldate=&quot;$year$last_month$yes_day&quot;                 else                         if [ $day = &quot;02&quot; ]; then                                 date=&quot;$last_month/$yes_day/$year&quot;                                 fulldate=&quot;$year$last_month$yes_day&quot;                         else                                 date=&quot;$month/$yes_day/$year&quot;                                 fulldate=&quot;$year$month$yes_day&quot;                         fi                 fi         fi fi  But my bad am getting the below error message Etime_script.sh: line 19: [06=01]: command not found Etime_script.sh: line 24: [06=01]: command not found DSolve gets stuck on system of differential equations with unassigned variable Does Two-Face die at the end of The Dark Knight? Does the Two-Face die in the final scene of the Dark Knight? If he does, then how does he become one of the long lasting rival of Batman? What is the differance between Linked and Appended data from external .blend files? Help! My master database is corrupt, I can't even bring the SQL instance online! What are my options to get my server back up?   I do have a backup of master, but the  asks me to start the instance in single-user mode, which I can't do!  (Note: I'm leaving this question unspecified as to SQL version, so as to be a more widely-applicable reference. There are some similar questions on DBA.SE, but none that involve the server unable to start.) Uniformly convergent implies equicontinuous I'm trying to prove that if I have a sequence of continuously differentiable functions $f_n$ that converge uniformly on $[a,b]$, then $\{f_n\}$ is equicontinuous for all $x_0 \in [a, b]$. My idea is to use uniform convergence to deal with the &quot;tail&quot; and then use continuity to deal with the finitely many $f_n$'s left. But I'm having trouble writing it down. Files list file for package missing -- dpkg warning I want to install Open JDK or Oracle JDK to my machine but I got an error during installation. The error is:  Selecting previously unselected package oracle-java8-installer. dpkg: warning: files list file for package 'unity-scope-gourmet' missing; assuming package has no files currently installed dpkg: warning: files list file for package 'unity-scope-guayadeque' missing; assuming package has no files currently installed dpkg: warning: files list file for package 'unity-scope-gmusicbrowser' missing; assuming package has no files currently installed dpkg: warning: files list file for package 'unity-scope-manpages' missing; assuming package has no files currently installed dpkg: warning: files list file for package 'unity-scope-firefoxbookmarks' missing; assuming package has no files currently installed dpkg: warning: files list file for package 'unity-scope-gdrive' missing; assuming package has no files currently installed dpkg: warning: files list file for package 'unity-scope-home' missing; assuming package has no files currently installed E: Sub-process /usr/bin/dpkg returned an error code (2)   I searched on Google and try to something for install/reinstall this packages. Finally i try to remove Unity. I faced this error for my every tries. I am using Xmonad. How can I fix this issue? Word for in-house jargon (c) Let $\mathcal{L}^*\subseteq\mathcal{L}^{\text{FOPC}}$ be a first order language of predicate calculus consisting of three unary function symbols $f,g,h$.  (i) Write down an $\mathcal{L}^*$-sentence $\phi$ such if $\mathcal{A}$ is an $\mathcal{L}^*$-structure with $\mathcal{A}\vDash\phi$ then the restriction of $h_\mathcal{A}$ to the range of $f_\mathcal{A}$ gives a one-to-one function onto the range of $g_\mathcal{A}$.  (ii) Write down an $\mathcal{L}^*$-sentence $\psi$ such that if $\mathcal{A}$ is an $\mathcal{L}^*$-structure with $\mathcal{A}\vDash\psi$ and the domain $A$ of $\mathcal{A}$ is finite then the cardinality $|A|$ is a square.    Part (i) is easy enough, but I'm having trouble with part (ii). I assume that you can use part (i). My initial idea was to use $h$ to ensure $|Range(f_A)| =|Range(g_A)|$ but I'm not sure where to go from there. Thanks. Measuring draw time of layer in ArcMap? I'd like to quantitatively measure the display performance of mosaic datasets, image service layers, raster layers, feature layers, etc. in ArcMap 10.  How can I measure the draw time of a particular layer (or the complete drawing process if that is the only option) in ArcMap? What are the interfaces, objects and events involved? Is the  class in .NET suitable for accurately measuring this type of operation?  Has anyone already created an ArcMap add-in or extension for this purpose? Should I disable google maps scroll wheel zoom? In most applications of google maps the scroll wheel will zoom the map instead of scrolling it.  Personally I find this confusing, and after years of using google maps, both on the google maps web site and embedded google maps, I still often make the mistake of trying to scroll the map with scroll wheel and end up zooming it instead.  The google maps API allows me to disable scrollwheel zoom when I embed a map in my page.  The question is should I disable it?  On the one hand scroll wheel zoom is unconventional in the context of the web as a whole - in the vast majority of cases the scroll wheel scrolls things.  On the other hand scroll wheel zoom is established convention for maps.  It definitely would be a better experience for me if scroll wheel zooming was disabled, but what about the web browsing population in general?  I did some searching on whether I should disable scroll zoom and couldn't find any guidelines. So, to scroll zoom or not to scroll zoom?