Logic For Displaying Events in a Calendar

Bonesnap

Hey everyone!

I have a custom-made event calendar that prints out a calendar on the page. The events are displayed below the calendar but are hidden by default and are only displayed when the user clicks the appropriate cell on the calendar (facilitated via JavaScript). The client has requested that the cells in the calendar that have an event be coloured differently than normal cells to indicate to users there's an event on that day. No other information is needed other than "is there an event on this day, if so, colour this cell differently".

Currently the calendar is being generated via a for loop. The logic for determining how many cells, rows, which day to start, etc. is all complete; however, I can't think of a way to do this other than running a SQL query for each iteration to check if there's an event on the particular day. I was hoping to avoid that. Right now when the page loads it generates the calendar based on a month and year value, which is also used to do the SQL query, so the query only has to run once, and then uses JavaScript to do showing/hiding.

What is the most efficient approach to something like this? Am I forced to run a query for each day?

Thanks for any insight!

dalecosp

What resource are you currently getting from the DB ... just the start and end days and so on?

Could you have it return an array/list of days, perhaps a multi-dimensional one with a flag for whether there is an event or not?

Bonesnap

The calendar is being generated completely independently from the database. The calendar only requires a month and year (which is also being passed to the query to pull the corresponding events). These values come from the GET variable in the URL or if they don't exist, then default to the current month and year.

As for what is being returned from the database... I'm not entirely sure lol. It's a .NET project (that unfortunately has fallen in my lap). All I know is I use a SqlDataReader and while it "reads" (so executing a while loop) I generate the events below the calendar. I didn't mention the .NET part specifically because I was just looking for logic and not code.

Bonesnap

Wait, this should work...

Query the database, get the results back. Run through it once and create that array you mentioned (before the calendar output). Do the calendar output and use that array. Then loop through the dataset again to generate the events after the calendar. One database call.

I'll give this a shot.

dalecosp

Bonesnap;11047423 wrote:
As for what is being returned from the database... I'm not entirely sure lol. It's a .NET project (that unfortunately has fallen in my lap).

I know how you feel; there's a couple well-worn CFML books in my overhead space that get pulled once in a blue moon; I type something, see if it works; if not, "WTH?" and if so, Save and go back to something I understand ;-)

maxxd

I've handled this in the past by querying only the date (day, actually, if you're looking at one discrete month at a time) from the database for the specified month. Don't worry about a flag if there's an event - you'll only have a result if there's an event. So while you're traipsing through the calendar build loop you'll know the day - if there's a corresponding index for that day in the results, you've got an event and can safely color the box. Sounds like you've got the logic to display the events figured out and working well.

Bonesnap

I have it working, but I had to query the database twice because data readers are "forward only", so once you read it once, you have to requery the database. And you have to keep the database connection open for them to work. I was also trying to use an array of integers to store the dates and then use that to compare in my for loop, but that simply wasn't working so I had to use an ArrayList which I remember using in college.

So I couldn't do it in a single query but at least I didn't have to query the database on each iteration of my loop, so I consider that a win.

dalecosp;11047427 wrote:
I know how you feel; there's a couple well-worn CFML books in my overhead space that get pulled once in a blue moon; I type something, see if it works; if not, "WTH?" and if so, Save and go back to something I understand ;-)

I think I mentioned this in another thread but my life has depended on Stack Overflow for the last few weeks while working on this project. I haven't touched .NET since college. It took me about a day and a half just to be able to connect to a MSSQL database. I found a site that had dozens and dozens of different connection strings. I'm sure if you were a .NET developer and it's what you worked with your whole career it would seem straightforward, but come on Microsoft, this sort of thing can't be streamlined? And honestly it's weird going from a loosely-typed language (PHP) to a very strict language like C#. There's no implicit conversions anywhere. Can't tell you how many times I've had compile errors because of IF statements and implicitly converting expressions. At least I don't have to do it in VB, right? 🙂

Derokorian

Bonesnap;11047441 wrote:
I have it working, but I had to query the database twice because data readers are "forward only", so once you read it once, you have to requery the database. And you have to keep the database connection open for them to work. I was also trying to use an array of integers to store the dates and then use that to compare in my for loop, but that simply wasn't working so I had to use an ArrayList which I remember using in college.

Its pretty common practice in the .NET projects I've worked with to loop through the dataset, put the values in a DataRow as part of a DataTable, and work with the DataTable as many times as needed without keeping the connection or being subject to the "read once and done" problem. Though, I can't say I've been impressed by the .NET code I've worked with so it is of course flawed in that now the entire result set is in memory to work (which could be problematic in certain queries/situations).

Bonesnap

I just find .NET code to be very verbose, but that could just be me since I am used to PHP, where you don't have to declare variables with a strict data type. Everything has to be declared and from my experience with .NET, even in college, it follows the "everything is an object" methodology (even strings are inherently objects) so you're constantly declaring instances of stuff which makes the code very verbose (didn't want to say bloated since that has different connotations).

I do know there are datasets, datarows, datatables, datagrids, datadatadatadatas, but I just wanted to loop through some results. Seems kinda ridiculous that the readers are forward only. I mean why can't you just start from the beginning again?

dalecosp

Derokorian;11047459 wrote:
Its pretty common practice in the .NET projects I've worked with to loop through the dataset, put the values in a DataRow as part of a DataTable, and work with the DataTable as many times as needed without keeping the connection or being subject to the "read once and done" problem. Though, I can't say I've been impressed by the .NET code I've worked with so it is of course flawed in that now the entire result set is in memory to work (which could be problematic in certain queries/situations).

To be fair, that is often done in PHP as well by intermediate coders who aren't thinking about scale. It's quite common to see/do:

if ($result) {

   $data = array();
   while ($row = $result->fetch_assoc()) {
      $data[] = $row['foo'];
   }
}

Which isn't a big deal until your result sets are tens of thousands (or millions) of lines ...

Bonesnap wrote:
I mean why can't you just start from the beginning again?

Probably the guy tasked with adding that functionality is still busy declaring his variables? :evilgrin: 😃

Bonesnap

I am also annoyed when I see code examples online that make sense logically, but the person providing the example or code omits the directives at the top of the code, so I have no idea what I need to "include" (using, in C#) to basically enable the specific class or functionality, and I'm forced to do a separate Google search to hopefully find it.

Would anyone happen to know why .NET is like this? Is it because of memory or something similar? Again it may just be because I am used to PHP, but why would most functionality of the language be "disabled" until explicitly enabled? Has this sort of approach ever been proposed for PHP in the past?

EDIT: I also keep getting compile errors because I am so used to working with strings in single quotes, which must be double quotes in .NET (or C#, at least). Driving me bonkers lol.

laserlight

dalecosp wrote:
To be fair, that is often done in PHP as well by intermediate coders who aren't thinking about scale. It's quite common to see/do:
(...)

In itself that can be fine: the data set can be limited in the query or database abstraction layer.

Bonesnap wrote:
I am also annoyed when I see code examples online that make sense logically, but the person providing the example or code omits the directives at the top of the code, so I have no idea what I need to "include" (using, in C#) to basically enable the specific class or functionality, and I'm forced to do a separate Google search to hopefully find it.

Would anyone happen to know why .NET is like this? Is it because of memory or something similar? Again it may just be because I am used to PHP, but why would most functionality of the language be "disabled" until explicitly enabled? Has this sort of approach ever been proposed for PHP in the past?

"Including" something for a class makes sense to me: it reflects separation of core language and standard library, and there are after all pros and cons to having some kind of autoload mechanism. Enabling functionality (as in language features) in this way though, is unusual unless it is for things that are deprecated or experimental.

Derokorian

AFAIK, the includes are for .NET framework functionality. Everything that makes C# a language is available, but if you want to use the framework you have to include what you want. This is no different than using require at the top of your script in PHP to include that one class from the Framework your using (IE ZF2, CI, Lithium, etc) when no autoloader is available (or allowed, my boss doesn't like autoloaders so we're have to explicitly require everything).

dalecosp

laserlight;11047467 wrote:
In itself that can be fine: the data set can be limited in the query or database abstraction layer.

Yes; I gave no context other than hinting that if you did it with a result set that was too large you'd eat up more RAM that you'd care to. Typically there's a "sane" memory_limit in php.ini, but it's still good to be aware that you could be shooting yourself in the foot by putting all the data you expect to need in an array without thinking about scale issues in the future; what worked for 1,000 data objects often doesn't work as well for 100,000+...

Bonesnap

laserlight;11047467 wrote:
"Including" something for a class makes sense to me: it reflects separation of core language and standard library, and there are after all pros and cons to having some kind of autoload mechanism. Enabling functionality (as in language features) in this way though, is unusual unless it is for things that are deprecated or experimental.

But then why not just "include" everything behind the scenes and have everything available? Why force the user to have to manually include different directives so he can get his work done? And furthermore, when I create a new .aspx file in my project, the corresponding .cs file has this at the top by default:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

Everything requires System, so to me that would be "core", but then you have to include it every time you want to use the language, which seems silly to me. I guess I don't see much of a difference between "core" and "standard library".

I totally get the idea that someone else has created a custom module (or whatever you want to call it) and you have to include it manually to use it, but for stuff that (to me) should be available out of the box I don't see the benefit in having to include some directive at the top to make it available. Using the above example I wouldn't be able to use the ArrayList class. It wouldn't even be available in my autocomplete or syntax highlighting. It's as if VS doesn't know what ArrayList is. But as soon as I add using System.Collections, it does. The sytax magically highlights and all the annoying red squiggly lines in my IDE go away.

In PHP if I want to use DateTime, I don't have to include something at the top of my file.

Derokorian;11047469 wrote:
AFAIK, the includes are for .NET framework functionality. Everything that makes C# a language is available, but if you want to use the framework you have to include what you want. This is no different than using require at the top of your script in PHP to include that one class from the Framework your using (IE ZF2, CI, Lithium, etc) when no autoloader is available (or allowed, my boss doesn't like autoloaders so we're have to explicitly require everything).

I'm not going to lie... I have (had) no idea that you can do C# without the .NET framework. I thought the two were more or less married, and that C# was a Microsoft "product" (sort of its variation of C) to be used within .NET and written in VS. I know you can write C# in other editors (though I always thought the support for syntax highlighting, autocomplete, etc. was subpar compared to VS).

Derokorian

Bonesnap;11047491 wrote:
I totally get the idea that someone else has created a custom module (or whatever you want to call it) and you have to include it manually to use it, but for stuff that (to me) should be available out of the box I don't see the benefit in having to include some directive at the top to make it available. Using the above example I wouldn't be able to use the ArrayList class. It wouldn't even be available in my autocomplete or syntax highlighting. It's as if VS doesn't know what ArrayList is. But as soon as I add using System.Collections, it does. The sytax magically highlights and all the annoying red squiggly lines in my IDE go away.

Your syntax highlighting would know what it is if you used a fully qualified name. For example, both of the following work:

using System;
// codes
System.Diagnostics.Process process = new System.Diagnostics.Process();

and

using Process = System.Diagnostics.Process;
// codes
Process process = new Process();

Just like in PHP, I can do

use Foor\Bar\Baz;

Baz = new Baz();

Baz = new \Foo\Bar\Baz();

Derokorian

Great explanation:

Each line has a purpose:

using System;

The above line of code tells the compiler to use System as a candidate prefix for types used in the source code. In this case, when the compiler sees use of the Console type later in the source code, it tries to find a type named Console, first in the current assembly, followed by all referenced assemblies. In this case the compiler fails to find such a type, since the name of the type is actually System.Console. The compiler then attempts to find a type named System.Console by using the System prefix from the using statement, and this time it succeeds. The using statement allows the programmer to state all candidate prefixes to use during compilation instead of always using full type names.

Weedpacket

Derokorian wrote:
The using statement allows the programmer to state all candidate prefixes to use during compilation instead of always using full type names.

...; you could write C# code using the .NET platform without any [font=monospace]using[/font] statements, but you'd need to write [font=monospace]System.Web.UI.WebControls.AdRotator skyscraper = new System.Web.UI.WebControls.AdRotator();[/font] instead of [font=monospace]AdRotator skyscraper = new AdRotator();[/font].

As far as "including" goes in the sense of "I want to use the code that is in this library, so make it available", that is handled by the project references (if you're using .NET then you'd reference the framework; if you're using COM objects you'd reference those, etc.).

Bonesnap

Derokorian;11047493 wrote:
Your syntax highlighting would know what it is if you used a fully qualified name.

I get how that works and I've seen it used before in code examples, I just don't understand why they force the coder to do it. Why not just "include" everything behind the scenes (so to speak) so I can just get on with what I am trying to accomplish instead of having to constantly add "using" statements at the top of my code. Want to work with a very specific database adapter? Better add another using statement. Send an email? That's a using. Want to use ArrayLists? That's a using. Want to add a control to your web page? That's a using. Need to use the Configuration Manager to access your database connection string? Oh you better believe that's a using.

That's why I was wondering if it was a memory issue or something of that nature.

Weedpacket

As Derokorian said, it's not "including" anything. It's for abbreviating names.

The using directive has two uses:
To allow the use of types in a namespace so that you do not have to qualify the use of a type in that namespace:
using System.Text;
To create an alias for a namespace or a type. This is called a using alias directive.
using Project = PC.MyCompany.Project;
https://msdn.microsoft.com/en-gb/library/sf0df423.aspx