What this 'null' check doing here...
-
He is just double checking. :)
:laugh: The same thing I told him when I saw this first time. :)
Previous -> Read "CLR via C#" by Jeffrey Ritcher. Current -> Exploring WCF thru Apress' "Pro WCF" by Chris Peiris and Dennis Mulder. Next -> Need to read "The Art of Computer Programming" by Donald E. Knuth.
-
Looks like a newbie whose prof in 101 programming hammered down checking objects before using them. This would be sensible if it were a thousand lines down in the code, but, if it is null where is the property/method to new it up?
Well, he is 4 yrs exp.....
Previous -> Read "CLR via C#" by Jeffrey Ritcher. Current -> Exploring WCF thru Apress' "Pro WCF" by Chris Peiris and Dennis Mulder. Next -> Need to read "The Art of Computer Programming" by Donald E. Knuth.
-
:)
Previous -> Read "CLR via C#" by Jeffrey Ritcher. Current -> Exploring WCF thru Apress' "Pro WCF" by Chris Peiris and Dennis Mulder. Next -> Need to read "The Art of Computer Programming" by Donald E. Knuth.
-
It isn't really filling the list, it's replacing the reference with the result of that method call. I don't think that's what he meant though. A bit pedantic, I'm sorry.
I think the point was that
List employees = GetEmployees();could just as well have been used to create a null or non-null employees object because the if statement would never be false for a statement that could produce a null result. In fact you might want to execute
if (employees == null) throw...after executing the above line because now you are in a situation where the if statement could be true or false even if the current coding of the routine would never return null. (speaking of being pedantic...)
-
Do you two realize how much money you just cost CP with this waste of disk space? You better click on some ads to pay for your mistakes.
There are only 10 types of people in the world, those who understand binary and those who don't.
What was that message??, now its not there
Previous -> Read "CLR via C#" by Jeffrey Ritcher. Current -> Exploring WCF thru Apress' "Pro WCF" by Chris Peiris and Dennis Mulder. Next -> Need to read "The Art of Computer Programming" by Donald E. Knuth.
-
Guess I don't know c# well enough, but I didn't this you could use any comparison operator against NULL. it's probably bad practice to even if the language allows it.
Mark Starr wrote:
I didn't this you could use any comparison operator against NULL
You're mixing up SQL with C# as well as "this" vs "think". SQL isn't case sensitive and comparison operators won't work with null, NULL, or NuLl where all versions of the null keyword are valid. In C#, NULL is nonsense unless you've declared an object name NULL and the language is designed to make comparisons (==, !=) with null
-
But that's not the case I have verified the previous versions from source control...
Previous -> Read "CLR via C#" by Jeffrey Ritcher. Current -> Exploring WCF thru Apress' "Pro WCF" by Chris Peiris and Dennis Mulder. Next -> Need to read "The Art of Computer Programming" by Donald E. Knuth.
lol. Then its probably just a brain fart, or late night coding session :)
-
The only thing that I can think of is technically new doesn't guarantee that the variable initialization will take place. In programming languages like c++ it could return null. This could happen if the memory was so fragmented that the allocation failed. However, instead of returning null in C# I believe it throws a out of memory exception. I have only seen this done in system critical embedded systems.
Michael Losinski wrote:
The only thing that I can think of is technically new doesn't guarantee that the variable initialization will take place.
Who cares? If the "if" check returns true, the result of calling the routine could make it null. If it's mission critical, initialize it by calling the function and then throw it when the function sets it to null. (Which it doesn't seem to check for, when that is a very possible result of calling the function.) If you are so constrained by memory the new would fail, it'd fail in the function too, thereby throwing an error the code doesn't check for(catch).
-
Well, he is 4 yrs exp.....
Previous -> Read "CLR via C#" by Jeffrey Ritcher. Current -> Exploring WCF thru Apress' "Pro WCF" by Chris Peiris and Dennis Mulder. Next -> Need to read "The Art of Computer Programming" by Donald E. Knuth.
-
Mohammed Hameed wrote:
Well, he is 4 yrs exp....
So, he IS inexperienced! :-D (I started coding in '74. Late start, '05 on C#.)
Ohh, is that?
Previous -> Read "CLR via C#" by Jeffrey Ritcher. Current -> Exploring WCF thru Apress' "Pro WCF" by Chris Peiris and Dennis Mulder. Next -> Need to read "The Art of Computer Programming" by Donald E. Knuth.
-
What was that message??, now its not there
Previous -> Read "CLR via C#" by Jeffrey Ritcher. Current -> Exploring WCF thru Apress' "Pro WCF" by Chris Peiris and Dennis Mulder. Next -> Need to read "The Art of Computer Programming" by Donald E. Knuth.
-
Weird, I wonder why they were removed. They just had a ton of smiley face icons.
There are only 10 types of people in the world, those who understand binary and those who don't.
May be because of "Smiley Overflows" :laugh:
Previous -> Read "CLR via C#" by Jeffrey Ritcher. Current -> Exploring WCF thru Apress' "Pro WCF" by Chris Peiris and Dennis Mulder. Next -> Need to read "The Art of Computer Programming" by Donald E. Knuth.
-
Michael Losinski wrote:
The only thing that I can think of is technically new doesn't guarantee that the variable initialization will take place.
Who cares? If the "if" check returns true, the result of calling the routine could make it null. If it's mission critical, initialize it by calling the function and then throw it when the function sets it to null. (Which it doesn't seem to check for, when that is a very possible result of calling the function.) If you are so constrained by memory the new would fail, it'd fail in the function too, thereby throwing an error the code doesn't check for(catch).
Yes you could the code down to one line of code. You could catch the exception somewhere else, so I suppose the question could then become what do you do in a mission critical system when outofmemory exception or an allocation fails, therefore allowing you to gracefully shutdown. First thing that comes to mind is if the current thread is not mission critical you can kill that can free up some memory. Second, you could have a fail-safe that would allow you to kill all non-mission critical threads thus freeing memory. With the right permissions you could also kill the other applications. I've never implemented one but you could also have a "memory para-shoot" that at the start of the program allocates a chunk of memory and frees it when needed. I suppose allot of it depend on the system and requirements.
-
Mark Starr wrote:
I didn't this you could use any comparison operator against NULL
You're mixing up SQL with C# as well as "this" vs "think". SQL isn't case sensitive and comparison operators won't work with null, NULL, or NuLl where all versions of the null keyword are valid. In C#, NULL is nonsense unless you've declared an object name NULL and the language is designed to make comparisons (==, !=) with null
Yup: I don't know C# well enough. Agreed. And, I didn't capitalize the 'i' at the beginning of the next sentence.
-
List<Employee> employees = new List<Employee>();
if (employees != null){
employees = GetEmployees();
}Previous -> Read "CLR via C#" by Jeffrey Ritcher. Current -> Exploring WCF thru Apress' "Pro WCF" by Chris Peiris and Dennis Mulder. Next -> Need to read "The Art of Computer Programming" by Donald E. Knuth.
it could make sense if it was a code update... let say it was like:
List<Employee> employees = GetEmployessFromSucursal(sucursalID);
if (employees != null){
employees = GetEmployees();//Get employes from other source
}then for some reason the code was updated or copy&paste... there is also a proba that the IF used to have some other parameter and an ELSE... so again code that was not finally updated to the best final form.
-
List<Employee> employees = new List<Employee>();
if (employees != null){
employees = GetEmployees();
}Previous -> Read "CLR via C#" by Jeffrey Ritcher. Current -> Exploring WCF thru Apress' "Pro WCF" by Chris Peiris and Dennis Mulder. Next -> Need to read "The Art of Computer Programming" by Donald E. Knuth.
Now a smart compiler should probably want about this. Something like when comparing signed and unsigned int's in C and it warns that the statement is always true (or false) due to conversion rules. Seems like maybe (I know.. "maybe?!?!") a programmer that didn't know what they're doing. That you have to first "create" the list, so you can "fill it in" with the GetEmployees() values or something. Along the same lines as novice programmers that create and assign a local number (or string) variable with a constant value because the function was prototyped with that data type, rather than pass the same constant number inline to the call. Could be worse.. I've seen this in [employed to write] software:
#define ZERO 0
#define ONE 1
#define TWO 2:doh:
-
Now a smart compiler should probably want about this. Something like when comparing signed and unsigned int's in C and it warns that the statement is always true (or false) due to conversion rules. Seems like maybe (I know.. "maybe?!?!") a programmer that didn't know what they're doing. That you have to first "create" the list, so you can "fill it in" with the GetEmployees() values or something. Along the same lines as novice programmers that create and assign a local number (or string) variable with a constant value because the function was prototyped with that data type, rather than pass the same constant number inline to the call. Could be worse.. I've seen this in [employed to write] software:
#define ZERO 0
#define ONE 1
#define TWO 2:doh:
Thanks.
My Reading-o-Meter
Previous -> Read "CLR via C#" by Jeffrey Richter. Current -> Exploring WCF thru Apress' "Pro WCF" by Chris Peiris and Dennis Mulder. Next -> Need to read "The Art of Computer Programming" by Donald E. Knuth.
-
it could make sense if it was a code update... let say it was like:
List<Employee> employees = GetEmployessFromSucursal(sucursalID);
if (employees != null){
employees = GetEmployees();//Get employes from other source
}then for some reason the code was updated or copy&paste... there is also a proba that the IF used to have some other parameter and an ELSE... so again code that was not finally updated to the best final form.
Thanks.
My Reading-o-Meter
Previous -> Read "CLR via C#" by Jeffrey Richter. Current -> Exploring WCF thru Apress' "Pro WCF" by Chris Peiris and Dennis Mulder. Next -> Need to read "The Art of Computer Programming" by Donald E. Knuth.
-
Now a smart compiler should probably want about this. Something like when comparing signed and unsigned int's in C and it warns that the statement is always true (or false) due to conversion rules. Seems like maybe (I know.. "maybe?!?!") a programmer that didn't know what they're doing. That you have to first "create" the list, so you can "fill it in" with the GetEmployees() values or something. Along the same lines as novice programmers that create and assign a local number (or string) variable with a constant value because the function was prototyped with that data type, rather than pass the same constant number inline to the call. Could be worse.. I've seen this in [employed to write] software:
#define ZERO 0
#define ONE 1
#define TWO 2:doh:
-
Yup: I don't know C# well enough. Agreed. And, I didn't capitalize the 'i' at the beginning of the next sentence.
This thread started with:
List employees = new List();
if (employees != null){
employees = GetEmployees();There are layers of things wrong with just this bit of code. "employees = new ..." created a new object, it is impossible for "if (employees != null)" to return false. (Others have said memory critical operations might have problems, but that can't happen because if it did happen, the behavior of C# is to throw an error. In which case, "if" would never execute. THEN it executes "employees = GetEmployees()" which threw the "=..." part of "employees = new ..." into the trash. NOW employees may or may not be null and no if checking if it is null or not is done, it just assumes that since it wasn't null it still isn't null. It is incredible how much bad code can be compressed into so little space, so it is worth posting in the weird and wonderful. The following code has exactly the same amount of effective error checking as the first bit of code:
List employees = GetEmployees();
Sorry, I wasn't trying to bash you about your knowledge. (I was teasing you about your mistyping, thinking you wrote it while tired and made an easy mistake to make when you are tired.) The SQL part of what I said was just trying to teach you a little bit of the difference between the two languages. Everyone is ignorant in some things in their lives. Nothing wrong with that. There is something wrong with wanting to be ignorant and I didn't think that was happening with you.