Is there a shorter version of IF statement to do this?
if (el.type == ElementType.Type1 || el.type == ElementType.Type2)
You could use an extension method, but would this really be much better?
Throw this on a static class:
public static bool IsOneOf(this ElementType self, params ElementType[] options)
{
return options.Contains(self);
}
And then you can do:
if (el.type.IsOneOf(ElementType.Type1, ElementType.Type2)) {
However, this will be a lot slower than your if statement, as there is an implicit array initialization followed by an array traversal, as opposed to (at the most) two compares and branches.
Consider ElementType is defined as
enum ElementType
{
Type1,
Type2,
Type3
}
In this particular case you may write if(el.type<ElementType3)
By default Type1 equals to 0, Type2 equals 1, etc
If you have only 2 values, I strongly suggest to use the code you posted, because is likely the most readable, elegant and fast code possible (IMHO).
But if you have more cases like that and more complicated, you could think to use a switch statement:
switch (el.type)
{
case ElementType.Type1:
case ElementType.Type2:
case ElementType.Type3:
//code here
break;
case ElementType.Type4:
case ElementType.Type5:
//code here
break;
case ElementType.Type6:
//code here
break;
}
that translated in if statements would be:
if (el.type == ElementType.Type1 ||
el.type == ElementType.Type2 ||
el.type == ElementType.Type3 )
{
// code here
}else if(el.type == ElementType.Type4 ||
el.type == ElementType.Type5)
{
// code here
}else if(el.type == ElementType.Type6)
{
// code here
}
They're perfectly equal to me, but the switch seems more readable/clearer, and you need to type less (i.e. it's "shorter" in term of code length) :)
You can try this:
if(new [] { ElementType.Type1, ElementType.Type2 }.Contains(el.type))
(turns out, that takes even more characters)
I guess you're referring to an IN() clause or some such? Not really... Well, sort of... You can do something like:
if ((new [] { ElementType.Type1, ElementType.Type2}).Contains(el.type)) {...}
But that's not going to be anywhere near as performant (or brief) as what you're already doing. You can also do
if (el.type == ElementType.Type1 | el.type == ElementType.Type2)
but that doesn't do short-circuit evaluation, so you rarely want to use that operator. My advice is to stick with what you have.
The brief answer is no. There isn't C# language construct that lets you combine object comparisons. But as many people have mentioned before, creating a collection of your types is probably your best bet in creating a shorter if statement. However that sacrifices quite a bit in the area of performance. I would stick with the OR statement.
There is no better way to optimize your code. As other users have shown, you can optimize an if else.
But a type of if statement I have thought about, in your case especially, would be
if(X > [Y || Z || A])
But that doesn't exist, and isn't as clean as the current if (X > Y || X > Z || X > A)
(This is more of a response to Cody Gray)
If this is a common logic comparison in your code that shows up alot I'd just write a method to handle it.
private bool isType1OrType2(ElementType type)
{
return type == ElementType.Type1 || type == ElementType.Type2;
}
then you can do
if(isType1OrType2(el.type))
You could also make this an extension method like so
public static bool isType1OrType2(this ElementType type)
{
return type == ElementType.Type1 || type == ElementType.Type2;
}
so the code would read a little nicer
if(el.type.isType1OrType2())
But then you have to have a static class but you can decide if it's worth it. I personally would not write a method to take a collection of types to compare to unless you find that you are comparing the type to many different combinations. I also would not even bother changing the code at all if this is the only place you make this type of comparison.
i dont think there is a way to optimize your statement
In short: nothing reasonable (reasonable in terms of code readability and performance optimisation). I wouldn't recommend the ternary operator for this kind of comparison either.
The actual if can be shortened to 5 characters ;)
bool b = (el.type == ElementType.Type1) | (el.type == ElementType.Type2);
if(b){...}
Don't do this, it is stupid and confusing unless you have a finite-state automaton.
enum MyEnum
{
A,
B,
C
}
private readonly Dictionary<MyEnum, Action> _handlers = new Dictionary<MyEnum, Action>
{
{MyEnum.A,()=>Console.Out.WriteLine("Foo")},
{MyEnum.B,()=>Console.Out.WriteLine("Bar")},
};
public static void ActOn(MyEnum e)
{
Action handler = null;
if (_handlers.TryGetValue(e, out handler) && handler != null)
{
handler();
}
}
Another approach would be to do some bitwise comparison, but really not worth it again.
private void ActWithCast(MyEnum e)
{
const int interest = (int)MyEnum.A | (int)MyEnum.B;
if (0 != ((int)e & interest))
{
Console.Out.WriteLine("Blam");
}
}
If the ElementType is an enum there is a shorter way to do it:
[Flags]
public enum ElementType
{
Type1 = 1,
Type2 = 2,
Type3 = 4,
}
...
tElementType.HasFlag(ElementType.Type1 | ElementType.Type2);
You do not need the [Flags] attribute to use HasFlag, but the values of each of them do need to follow that pattern.
Related
Any easier way to write this if statement?
if (value==1 || value==2)
For example... in SQL you can say where value in (1,2) instead of where value=1 or value=2.
I'm looking for something that would work with any basic type... string, int, etc.
How about:
if (new[] {1, 2}.Contains(value))
It's a hack though :)
Or if you don't mind creating your own extension method, you can create the following:
public static bool In<T>(this T obj, params T[] args)
{
return args.Contains(obj);
}
And you can use it like this:
if (1.In(1, 2))
:)
A more complicated way :) that emulates SQL's 'IN':
public static class Ext {
public static bool In<T>(this T t,params T[] values){
foreach (T value in values) {
if (t.Equals(value)) {
return true;
}
}
return false;
}
}
if (value.In(1,2)) {
// ...
}
But go for the standard way, it's more readable.
EDIT: a better solution, according to #Kobi's suggestion:
public static class Ext {
public static bool In<T>(this T t,params T[] values){
return values.Contains(t);
}
}
C# 9 supports this directly:
if (value is 1 or 2)
however, in many cases: switch might be clearer (especially with more recent switch syntax enhancements). You can see this here, with the if (value is 1 or 2) getting compiled identically to if (value == 1 || value == 2).
Is this what you are looking for ?
if (new int[] { 1, 2, 3, 4, 5 }.Contains(value))
If you have a List, you can use .Contains(yourObject), if you're just looking for it existing (like a where). Otherwise look at Linq .Any() extension method.
Using Linq,
if(new int[] {1, 2}.Contains(value))
But I'd have to think that your original if is faster.
Alternatively, and this would give you more flexibility if testing for values other than 1 or 2 in future, is to use a switch statement
switch(value)
{
case 1:
case 2:
return true;
default:
return false
}
If you search a value in a fixed list of values many times in a long list, HashSet<T> should be used. If the list is very short (< ~20 items), List could have better performance, based on this test
HashSet vs. List performance
HashSet<int> nums = new HashSet<int> { 1, 2, 3, 4, 5 };
// ....
if (nums.Contains(value))
Generally, no.
Yes, there are cases where the list is in an Array or List, but that's not the general case.
An extensionmethod like this would do it...
public static bool In<T>(this T item, params T[] items)
{
return items.Contains(item);
}
Use it like this:
Console.WriteLine(1.In(1,2,3));
Console.WriteLine("a".In("a", "b"));
You can use the switch statement with pattern matching (another version of jules's answer):
if (value switch{1 or 3 => true,_ => false}){
// do something
}
Easier is subjective, but maybe the switch statement would be easier? You don't have to repeat the variable, so more values can fit on the line, and a line with many comparisons is more legible than the counterpart using the if statement.
In vb.net or C# I would expect that the fastest general approach to compare a variable against any reasonable number of separately-named objects (as opposed to e.g. all the things in a collection) will be to simply compare each object against the comparand much as you have done. It is certainly possible to create an instance of a collection and see if it contains the object, and doing so may be more expressive than comparing the object against all items individually, but unless one uses a construct which the compiler can explicitly recognize, such code will almost certainly be much slower than simply doing the individual comparisons. I wouldn't worry about speed if the code will by its nature run at most a few hundred times per second, but I'd be wary of the code being repurposed to something that's run much more often than originally intended.
An alternative approach, if a variable is something like an enumeration type, is to choose power-of-two enumeration values to permit the use of bitmasks. If the enumeration type has 32 or fewer valid values (e.g. starting Harry=1, Ron=2, Hermione=4, Ginny=8, Neville=16) one could store them in an integer and check for multiple bits at once in a single operation ((if ((thisOne & (Harry | Ron | Neville | Beatrix)) != 0) /* Do something */. This will allow for fast code, but is limited to enumerations with a small number of values.
A somewhat more powerful approach, but one which must be used with care, is to use some bits of the value to indicate attributes of something, while other bits identify the item. For example, bit 30 could indicate that a character is male, bit 29 could indicate friend-of-Harry, etc. while the lower bits distinguish between characters. This approach would allow for adding characters who may or may not be friend-of-Harry, without requiring the code that checks for friend-of-Harry to change. One caveat with doing this is that one must distinguish between enumeration constants that are used to SET an enumeration value, and those used to TEST it. For example, to set a variable to indicate Harry, one might want to set it to 0x60000001, but to see if a variable IS Harry, one should bit-test it with 0x00000001.
One more approach, which may be useful if the total number of possible values is moderate (e.g. 16-16,000 or so) is to have an array of flags associated with each value. One could then code something like "if (((characterAttributes[theCharacter] & chracterAttribute.Male) != 0)". This approach will work best when the number of characters is fairly small. If array is too large, cache misses may slow down the code to the point that testing against a small number of characters individually would be faster.
Using Extension Methods:
public static class ObjectExtension
{
public static bool In(this object obj, params object[] objects)
{
if (objects == null || obj == null)
return false;
object found = objects.FirstOrDefault(o => o.GetType().Equals(obj.GetType()) && o.Equals(obj));
return (found != null);
}
}
Now you can do this:
string role= "Admin";
if (role.In("Admin", "Director"))
{
...
}
public static bool EqualsAny<T>(IEquatable<T> value, params T[] possibleMatches) {
foreach (T t in possibleMatches) {
if (value.Equals(t))
return true;
}
return false;
}
public static bool EqualsAny<T>(IEquatable<T> value, IEnumerable<T> possibleMatches) {
foreach (T t in possibleMatches) {
if (value.Equals(t))
return true;
}
return false;
}
I had the same problem but solved it with a switch statement
switch(a value you are switching on)
{
case 1:
the code you want to happen;
case 2:
the code you want to happen;
default:
return a value
}
I have to check writerId is not equal to 0 or 1. here is what I wrote.
int writerId = foo();
if(writerId != 0 && writerId != 1)
{
// do something
}
Is there any short way to write the same if statement?
This is shorter, but considerably harder to understand:
if ((writerId & ~1) != 0)
The writerId & ~1 operation unsets the least significant bit in the number -- the only two numbers that would be equal to 0 after this operation are 1 and 0, so if the result is not 0 then it must not have been 0 or 1.
However, you are severely sacrificing readability. Sometimes the shortest code is not the most readable. I would stick with what you have.
If readability is a concern when viewing this piece of code.. you could always move it into its own boolean method so that it reads nicer in the context of the other code:
bool IsValid(int writerId) {
return writerId != 0 && writerId != 1;
}
Then your code can at least read a little bit nicer:
if (IsValid(writerId)) {
// do something
}
..I will leave the appropriate naming for the method up to you. I generally do this if there is no easier way to make the code read nicer without it becoming more complex.
You can try this:
if (foo() >> 1 != 0)
{
// do something
}
This happened to be a reoccuring thing in my daily work. I wrote an extension for it at some point:
public static class GenericExtensions
{
public static bool EqualsAny<T>(this T value, params T[] comparables)
{
return comparables.Any(element => object.Equals(value, element));
}
public static bool EqualsNone<T>(this T value, params T[] comparables)
{
return !EqualsAny(value, comparables);
}
}
So instead of (writerId != 0 && writerId != 1) you can write (!writerId.EqualsAny(0, 1)) or (writerId.EqualsNone(0, 1)). In this case, I probably wouldn't use the EqualsNone method, because it actually lowers readability. I might not use the method for this case at all anyway. It mostly helps with readability with long enum names that would cause long or wrapped lines. And as always it's a matter of opinion at any rate. ;)
I have a very quick question about the best way to use two variables. Essentially I have an enum and an int, the value for which I want to get within several ifs. Should I declare them outside the if's or inside - consider the following examples:
e.g.a:
public void test() {
EnumName? value = null;
int distance = 0;
if(anotherValue == something) {
distance = 10;
value = getValue(distance);
}
else if(anotherValue == somethingElse) {
distance = 20;
value = getValue(distance);
}
if (value == theValueWeWant){
//Do something
}
OR
e.g.2
public void test() {
if(anotherValue == something) {
int distance = 10;
EnumType value = getValue(distance);
if (value == theValueWeWant){
//Do something
}
else if(anotherValue == somethingElse) {
int distance = 20;
EnumType value = getValue(distance);
if (value == theValueWeWant){
//Do something
}
}
I am just curious which is best? or if there is a better way?
Purely in terms of maintenance, the first code block is better as it does not duplicate code (assuming that "Do something" is the same in both cases).
In terms of performance, the difference should be negligible. The second case does generate twice as many locals in the compiled IL, but the JIT should notice that their usage does not overlap and optimize them away. The second case is also going to cause emission of the same code twice (if (value == theValueWeWant) { ...), but this should also not cause any significant performance penalty.
(Though both aspects of the second example will cause the compiled assembly to be very slightly larger, more IL does not always imply worse performance.)
Both examples do two different things:
Version 1 will run the same code if you get the desired value, where as Version 2 will potentially run different code even if you get the desired value.
There's a lot of possible (micro)optimizations you could do.
For Example, if distance is only ever used in getValue(distance), you could get rid of it entirely:
/*Waring, micro-optimization!*/
public void test() {
EnumType value = getValue((anotherValue == something) ? 10 : (anotherValue == somethingElse) ? 20 : 0);
if (value == theValueWeWant){
//Do something
}
}
If you wish to use those later on, then g for the second method. Those variables will be lost as soon as they're out of scope.
Even if you don't want to use them later, declaring them before the if's is something you should do, to avoid code repetition.
This question is purely a matter of style and hence has no correct answer, only opinions
The C# best practice is generally to declare variables in the scope where they are used. This would point to the second example as the answer. Even though the types and names are the same, they represent different uses and should be constrained to the blocks in which they are created.
Cyclomatic Complexity will be high for methods with a high number of decision statements including if/while/for statements. So how do we improve on it?
I am handling a big project where I am supposed to reduced the CC for methods that have CC > 10. And there are many methods with this problem. Below I will list down some eg of code patterns (not the actual code) with the problems I have encountered. Is it possible that they can be simplified?
Example of cases resulting in many decision statements:
Case 1)
if(objectA != null) //objectA is a pass in as a parameter
{
objectB = doThisMethod();
if(objectB != null)
{
objectC = doThatMethod();
if(objectC != null)
{
doXXX();
}
else{
doYYY();
}
}
else
{
doZZZ();
}
}
Case 2)
if(a < min)
min = a;
if(a < max)
max = a;
if(b > 0)
doXXX();
if(c > 0)
{
doYYY();
}
else
{
doZZZ();
if(c > d)
isTrue = false;
for(int i=0; i<d; i++)
s[i] = i*d;
if(isTrue)
{
if(e > 1)
{
doALotOfStuff();
}
}
}
Case 3)
// note that these String Constants are used elsewhere as diff combination,
// so you can't combine them as one
if(e.PropertyName.Equals(StringConstants.AAA) ||
e.PropertyName.Equals(StringConstants.BBB) ||
e.PropertyName.Equals(StringConstants.CCC) ||
e.PropertyName.Equals(StringConstants.DDD) ||
e.PropertyName.Equals(StringConstants.EEE) ||
e.PropertyName.Equals(StringConstants.FFF) ||
e.PropertyName.Equals(StringConstants.GGG) ||
e.PropertyName.Equals(StringConstants.HHH) ||
e.PropertyName.Equals(StringConstants.III) ||
e.PropertyName.Equals(StringConstants.JJJ) ||
e.PropertyName.Equals(StringConstants.KKK))
{
doStuff();
}
Case 1 - deal with this simply by refactoring into smaller functions. E.g. the following snippet could be a function:
objectC = doThatMethod();
if(objectC != null)
{
doXXX();
}
else{
doYYY();
}
Case 2 - exactly the same approach. Take the contents of the else clause out into a smaller helper function
Case 3 - make a list of the strings you want to check against, and make a small helper function that compares a string against many options (could be simplified further with linq)
var stringConstants = new string[] { StringConstants.AAA, StringConstants.BBB etc };
if(stringConstants.Any((s) => e.PropertyName.Equals(s))
{
...
}
You should use the refactoring Replace Conditional with Polymorphism to reduce CC.
The difference between conditional an polymorphic code is that the in polymorphic code the decision is made at run time. This gives you more flexibility to add\change\remove conditions without modifying the code. You can test the behaviors separately using unit tests which improves testability. Also since there will be less conditional code means that the code is easy to read and CC is less.
For more look into behavioral design patterns esp. Strategy.
I would do the first case like this to remove the conditionals and consequently the CC. Moreover the code is more Object Oriented, readable and testable as well.
void Main() {
var objectA = GetObjectA();
objectA.DoMyTask();
}
GetObjectA(){
return If_All_Is_Well ? new ObjectA() : new EmptyObjectA();
}
class ObjectA() {
DoMyTask() {
var objectB = GetObjectB();
var objectC = GetObjectC();
objectC.DoAnotherTask(); // I am assuming that you would call the doXXX or doYYY methods on objectB or C because otherwise there is no need to create them
}
void GetObjectC() {
return If_All_Is_Well_Again ? new ObjectC() : new EmptyObjectC();
}
}
class EmptyObjectA() { // http://en.wikipedia.org/wiki/Null_Object_pattern
DoMyTask() {
doZZZZ();
}
}
class ObjectC() {
DoAnotherTask() {
doXXX();
}
}
class EmptyObjectB() {
DoAnotherTask() {
doYYY();
}
}
In second case do it the same was as first.
In the third case -
var myCriteria = GetCriteria();
if(myCriteria.Contains(curretnCase))
doStuff();
IEnumerable<Names> GetCriteria() {
// return new list of criteria.
}
I'm not a C# programmer, but I will take a stab at it.
In the first case I would say that the objects should not be null in the first place. If this is unavoidable (it is usually avoidable) then I would use the early return pattern:
if ( objectA == NULL ) {
return;
}
// rest of code here
The second case is obviously not realistic code, but I would at least rather say:
if ( isTrue && e > 1 ) {
DoStuff();
}
rather than use two separate ifs.
And in the last case, I would store the strings to be tested in an array/vector/map and use that containers methods to do the search.
And finally, although using cyclomatic complexity is "a good thing" (tm) and I use it myself, there are some functions which naturally have to be a bit complicated - validating user input is an example. I often wish that the CC tool I use (Source Monitor at http://www.campwoodsw.com - free and very good) supported a white-list of functions that I know must be complex and which I don't want it to flag.
The last if in case 2 can be simplified:
if(isTrue)
{
if(e > 1)
{
can be replaced by
if(isTrue && (e>1))
case 3 can be rewritten as:
new string[]{StringConstants.AAA,...}
.Contains(e.PropertyName)
you can even make the string array into a HashSet<String> to get O(1) performance.
At some time there will be a large amount of records, about 50,000.
with that in mind is the method GetEquipmentRecord up to the task.
thanks for you opinions.
c# ,net 2,0
public enum EquipShift { day, night };
public class EquipStatusList : List<EquipStatus>
{
string SerialFormat = "yyyyMMdd";
int _EquipmentID;
string _DateSerial;
EquipShift _Shift;
public EquipStatus GetEquipmentRecord(int equipmentID, EquipShift shift,
DateTime date)
{
_DateSerial = date.ToString(SerialFormat);
_Shift = shift;
_EquipmentID = equipmentID;
return this.Find(checkforEquipRecord);
}
bool checkforEquipRecord(EquipStatus equip)
{
if ((equip.EquipmentID == _EquipmentID)
&& (equip.Shift == _Shift)
&& (equip.Date.ToString(SerialFormat) == _DateSerial))
return true;
else
return false;
}
}
update :
I have changed the evaluation to read
if ((equip.Date.Date == _date.Date) && (equip.EquipmentID == _EquipmentID) && (equip.Shift == _Shift) )
not sure it that helps
Without commenting on your choice of algorithm, we can say that it probably is optimized enough.
You've got an O(n) find() in there; searching a sorted list with a binary search would be O(lg n) and searching a hash-set (or Dictionary in C# 2.0) would be O(1) for example. Hash-set would obviously be the way to go if you were calling this function often.
But bottlenecks are rarely where you expect them, so that you ask the question on this particular instance means that, on balance, profiling later will actually show that the big slowdowns are elsewhere.
You could speed this up considerably by implementing a suitable GetHashCode method and using a System.Collections.Generic.HashSet<EquipStatus> as the backing container. However, as it's not entirely clear how you are using your class (i.e. which other List<T> methods you use), ymmv.
No, it is not. Your whole construct is not able to be used in a multitasking environment. You are storing the details to search for as instance members of the class. I would take advantage of PLINQ (Parallel Linq) and the usual operators, also I wouldn't derive from the List itself, but offer an extension method like this:
public static EquipStatus GetEquipmentRecord(this IEnumerable<EquipStatus> list, int equipmentID, EquipShift shift, DateTime date)
{
return list.AsParallel().FirstOrDefault(e => e.EquipmentID == equipmentID && e.Shift == shift, e.Date.Date == date.Date);
}
By this, multiple searches at the same time are possible.
well an obvious way to improve your checkForEquipRecord method is to change
if ((equip.Date.Date == _date.Date) && (equip.EquipmentID == _EquipmentID) && (equip.Shift == _Shift) )
return true;
else
return false;
to just return (equip.Date.Date == _date.Date) && (equip.EquipmentID == _EquipmentID) && (equip.Shift == _Shift)
As far as efficiency goes, it might already be an optimization that the JIT compiler makes.