If (cmbBloodgroup.SelectedItem == null) Then             MessageBox.Show(&quot;Please select a blood group.&quot;) Endif  The error 'Expression expected' is on the second equal sign. When I clicked the 'Show potential fixes', it gave me 2 options: remove unnecessary parentheses, and invert if. The first option doesn't remove the error. The second option makes it like this: cmbBloodgroup.SelectedItem =IsNot null  But I want the condition for it to be null. Idk what I should change here. (I'm checking combobox. If it's empty, I want to show a messagebox)
I have this:  If String.IsNullOrEmpty(editTransactionRow.pay_id.ToString()) = False Then     stTransactionPaymentID = editTransactionRow.pay_id 'Check for null value End If   Now, when editTransactionRow.pay_id is Null Visual Basic throws an exception. Is there something wrong with this code?
O-Rings vs. Washers for Garden Hoses? Is it possible to install multiple instances of the same delphi service application? Simple question but I am confused.  What is the boundary of $S^2\times\mathbb{R}$? Is it just $S^2$?  What would be the general way to evaluate the boundary of a product manifold?  Thanks for the replies! What are the mechanics by which Time Dilation and Length Contraction occur? Resources for Blender Since asking for tutorials, videos, resources, links to other content or downloads is considered off topic here, this is a specifically created Community Wiki which gathers resources for Blender and it has been approved by the .  Just write in the appropriate answer/section. If you have concerns, questions, post a  question, so we don't clutter the comments, but you can link your meta question from the comments.  Questions regarding such resources are not allowed anymore, except for very specific and on topic requests (ask on  if you're unsure about your question). Follow the instructions made in the question about how to post, what can be posted, etc.  Learning             Assets    (also see: )   Reference Images/Blueprints (also see: )    Tools    (also see: )      Other   Special Interest ()     Also see the . TTY doesn't wait for password I upgraded from 16.04 to 18.04. When I press Ctrl+Alt+F3 I get the terminal which prompts for the username. When I type my username and press Enter, it doesn't wait for my password (its as if I pressed Enter without entering anything). Even if I enter something, the text shown in plaintext and then it keeps on saying my password is wrong. After few times, the screen is cleared and it prompts for my username again and the same loop goes on. What is the meaning of "would", and how to use it? What is the meaning of would, and which tense is it used in the following sentences?  For example,   That would be Ram calling. I'll answer it. (the meaning of would and which tense is used) The guy on the phone had southern accent. That would be Tom. (the meaning of would and which tense is used) “We saw a police helicopter overhead yesterday morning.” “Really? They would have been looking for those bank robbers.” (the meaning of would and which tense is used) You would have to say/do that. (Why is would used here? What happens to the meaning if would is removed?) John said he didn't steal any money. Well, he would, wouldn't he ? (Why is would used here?)   Why is would used in sentences 1, 2, and 3 to mean "presumption" instead of using other modals, such as: must and should? Does the meaning change if used others?   Can we use will, must, should and could in the place of would, without changing the meaning of sentences?   What kind of meanings would it make if they (will, must, should, and could) are used in the place of would?     I'd be grateful if you could answer me. What is the easiest way to strip a desktop edition to a server edition? We have installed Ubuntu desktop edition on our development server. Now that we have it in a data center we would like to strip it down to a server edition.  Is there an easy way of doing so rather than just going in and uninstalling packages by hand? How do properties work in Object Oriented MATLAB? I am trying to create a MATLAB class with a member variable that's being updated as a result of a method invocation, but when I try to change the property within the class it (apperently, from what I understood from MATLAB's memory management) creates a copy of the object and then modifies it, leaving the original object's property untouched.  classdef testprop       properties           numRequests=0;       end       methods           function Request(this, val)               disp(val);               this.numRequests=this.numRequests+1;           end       end   end     .  &gt;&gt; a=testprop; &gt;&gt; a.Request(9); &gt;&gt; a.Request(5);   &gt;&gt; a.numRequests    ans = 0 What is in the space between a nucleus of an atom and its electrons? Apparently $1+2+3+4+\ldots+n = \dfrac{n\times(n+1)}2$.  How? What's the proof? Or maybe it is self apparent just looking at the above?   PS: This problem is known as "The sum of the first $n$ positive integers". Why aren't logarithms defined for negative $x$? Given a logarithm is true, if and only if, $y = \log_b{x}$ and $b^y = x$ (and $x$ and $b$ are positive, and $b$ is not equal to $1$), are true, why aren't logarithms defined for negative numbers?  Why can't $b$ be negative? Take $(-2)^3 = -8$ for example. Turning that into a logarithm, we get $3 = \log_{(-2)}{(-8)}$ which is an invalid equation as $b$ and $x$ are not positive! Why is this? I'm using an unsigned repo in Ubuntu 16.04 from Debian multimedia:  deb http://www.deb-multimedia.org jessie main   To install deb-multimedia-keyring, I'm running:  apt-get update &amp;&amp; apt-get install deb-multimedia-keyring -y   This gives an error:  W: GPG error: http://www.deb-multimedia.org jessie InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 5C808C2B65558117 E: The repository 'http://www.deb-multimedia.org jessie InRelease' is not signed. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. I'm using  to go through JavaScript, and it's returning many suggestions to replace == (two equals signs) with === (three equals signs) when doing things like comparing idSele_UNVEHtype.value.length == 0 inside of an if statement.  Is there a performance benefit to replacing == with ===?   Any performance improvement would be welcomed as many comparison operators exist.  If no type conversion takes place, would there be a performance gain over ==? the structure "like for somebody to do something" The files are "ready to download" or "ready to be downloaded"? Both ways seem to be used quite interchangeably even though the first one doesn't seem grammatical to me (English is, however, my second language so I could be miles off here). What do you think? Performing test for homogeneity of variance without samples I'd like to perform a test for homogeneity of variance in r, but I don't have samples available to test.    I have the sample mean of each group, the sample deviation of each group, and the sample size of each group(100).  Brand    ybar_i  s_i    n_i --------------------------- LowTar   9.64    .291   100 A        10.22   .478   100 B        10.77   .372   100 C        11.57   .352   100 D        13.59   .469   100   I'm thinking I should use the Levene test from Lawstat package, but that requires samples to test.  Or I think I could use the Fmax test. but that also requires samples. I know that big O is used to describe the upper bound of a function, so doesn't this mean that if the upper bounds f and g are the same, they are the same function? If this is the case, then we can say that  f ∈ Θ(g) because if that were not the case, then the two upper bounds would not be the same and thus one would out grow the other. Is this correct? Is it possible to set the GPU fan speed using the default free ati driver?  My card (X1900) was deprecated in the fglrx drivers a while back.  The free drivers seem to work with 3D, Compiz and such, but running graphics intensive programs makes my GPU heat up and produce artifacts, while the GPU fan never seems to increase. (When set to 100% in Windows it makes a massively louder noise.) What's the fixed size of the suggested edit queue? We know that Stack Overflow has a suggested edit queue, visible to the users who have the  privilege. Someone said the queue has a fixed size.  What's the fixed size of the suggested edit queue?  Is it often that the queue gets filled up and users can no longer suggest edits?