Why use the params keyword?

c# params keyword
params ruby
what is params
c# params with other parameters
params python
params meaning
params js
c# params named arguments

I know this is a basic question, but I couldn't find an answer.

Why use it? if you write a function or a method that's using it, when you remove it the code will still work perfectly, 100% as without it. E.g:

With params:

static public int addTwoEach(params int[] args)
{
    int sum = 0;
    foreach (var item in args)
        sum += item + 2;
    return sum;
}

Without params:

static public int addTwoEach(int[] args)
{
    int sum = 0;
    foreach (var item in args)
       sum += item + 2;
    return sum;
}

With params you can call your method like this:

addTwoEach(1, 2, 3, 4, 5);

Without params, you can’t.

Additionally, you can call the method with an array as a parameter in both cases:

addTwoEach(new int[] { 1, 2, 3, 4, 5 });

That is, params allows you to use a shortcut when calling the method.

Unrelated, you can drastically shorten your method:

public static int addTwoEach(params int[] args)
{
    return args.Sum() + 2 * args.Length;
}

Why use the params keyword?, The "params" keyword in C# allows a method to accept a variable number of arguments. C# params works as an array of objects. By using� The "params" keyword in C# allows a method to accept a variable number of arguments. C# params works as an array of objects. By using params keyword in a method argument definition, we can pass a number of arguments.

Using params allows you to call the function with no arguments. Without params:

static public int addTwoEach(int[] args)
{
    int sum = 0;

    foreach (var item in args)
    {
        sum += item + 2;
    }

    return sum;
}

addtwoEach(); // throws an error

Compare with params:

static public int addTwoEach(params int[] args)
{
    int sum = 0;

    foreach (var item in args)
    {
        sum += item + 2;
    }

    return sum;
}

addtwoEach(); // returns 0

Generally, you can use params when the number of arguments can vary from 0 to infinity, and use an array when numbers of arguments vary from 1 to infinity.

Use Params Keyword in C#, While declaring a method, if you are not sure of the number of arguments passed as a parameter, then use the C# param arrays.The following� Why use it? if you write a function or a method that's using it, when you remove it the code will still work perfectly, 100% as without it. E.g: With params: static public int addTwoEach(params int[] args) { int sum = 0; foreach (var item in args) sum += item + 2; return sum; } Without params:

It allows you to add as many base type parameters in your call as you like.

addTwoEach(10, 2, 4, 6)

whereas with the second form you have to use an array as parameter

addTwoEach(new int[] {10,2,4,6})

Why do we use the params keyword in C#?, Params is an important keyword in C#. It is used as a parameter which can take the variable number of arguments. Important Point About� I know this is a basic question, but I couldn't find an answer. Why use it? if you write a function or a method that's using it, when you remove it the code will still work perfectly, 100% as without it. E.g: With params: static public int addTwoEach(params int[] args) { int sum = 0; foreach (var it

One danger with params Keyword is, if after Calls to the Method have been coded,

  1. someone accidentally / intentionally removes one/more required Parameters from the Method Signature, and
  2. one/more required Parameters immediately prior to the params Parameter prior to the Signature change were Type-Compatible with the params Parameter,

those Calls will continue to compile with one/more Expressions previously intended for required Parameters being treated as the optional params Parameter. I just ran into the worst possible case of this: the params Parameter was of Type object[].

This is noteworthy because developers are used to the compiler slapping their wrists with the much, much more common scenario where Parameters are removed from a Method with all required Parameters (because the # of Parameters expected would change).

For me, it's not worth the shortcut. (Type)[] without params will work with 0 to infinity # of Parameters without needing Overrides. Worst case is you'll have to add a , new (Type) [] {} to Calls where it doesn't apply.

Btw, imho, the safest (and most readable practice) is to:

  1. pass via Named Parameters (which we can now do even in C# ~2 decades after we could in VB ;P) (because:

    1.1. it's the only way that guarantees prevention of unintended values passed to Parameters after Parameter order, Compatible-Type and/or count change after Calls have been coded,

    1.2. it reduces those chances after a Parameter meaning change, because the likely new identifier name reflecting the new meaning is right next to the value being passed to it,

    1.3. it avoids having to count commas and jump back & forth from Call to Signature to see what Expression is being passed for what Parameter, and

    1.3.1. By the way, this reason alone should be plenty (in terms of avoiding frequent error-prone violations of the DRY Principle just to read the code not to mention also modify it), but this reason can be exponentially more important if there are one/more Expressions being Passed that themselves contain commas, i.e. Multi-Dimensional Array Refs or Multi-Parameter Function Calls. In that case, you couldn't even use (which even if you could, would still be adding an extra step per Parameter per Method Call) a Find All Occurrences in a Selection feature in your editor to automate the comma-counting for you.

    1.4. if you must use Optional Parameters (params or not), it allows you to search for Calls where a particular Optional Parameter is Passed (and therefore, most likely is not or at least has the possibility of being not the Default Value),

(NOTE: Reasons 1.2. and 1.3. can ease and reduce chances of error even on coding the initial Calls not to mention when Calls have to be read and/or changed.))

and

  1. do so ONE - PARAMETER - PER - LINE for better readability (because:

    2.1. it's less cluttered, and

    2.2. it avoids having to scroll right & back left (and having to do so PER - LINE, since most mortals can't read the left part of multiple lines, scroll right and read the right part)).

    2.3. it's consistent with the "Best Practice" we've already evolved into for Assignment Statements, because every Parameter Passed is in essence an Assignment Statement (assigning a Value or Reference to a Local Variable). Just like those who follow the latest "Best Practice" in Coding Style wouldn't dream of coding multiple Assignment Statements per line, we probably shouldn't (and won't once "Best Practice" catches up to my "genius" ;P ) do so when Passing Parameters.

NOTES:

  1. Passing in Variables whose names mirror the Parameters' doesn't help when:

    1.1. you're passing in Literal Constants (i.e. a simple 0/1, false/true or null that even "'Best Practices'" may not require you use a Named Constant for and their purpose can't be easily inferred from the Method name),

    1.2. the Method is significantly lower-level / more generic than the Caller such that you would not want / be able to name your Variables the same/similar to the Parameters (or vice versa), or

    1.3. you're re-ordering / replacing Parameters in the Signature that may result in prior Calls still Compiling because the Types happen to still be compatible.

  2. Having an auto-wrap feature like VS does only eliminates ONE (#2.2) of the 8 reasons I gave above. Prior to as late as VS 2015, it did NOT auto-indent (!?! Really, MS?!?) which increases severity of reason #2.1.

VS should have an option that generates Method Call snippets with Named Parameters (one per line of course ;P) and a compiler option that requires Named Parameters (similar in concept to Option Explicit in VB which, btw, the requirement of was prolly once thought equally as outrageous but now is prolly required by "'Best Practices'"). In fact, "back in my day" ;), in 1991 just months into my career, even before I was using (or had even seen) a language with Named Parameters, I had the anti-sheeple / "just cuz you can, don't mean you should" / don't blindly "cut the ends of the roast" sense enough to simulate it (using in-line comments) without having seen anyone do so. Not having to use Named Parameters (as well other syntax that save "'precious'" source code keystrokes) is a relic of the Punch Card era when most of these syntaxes started. There's no excuse for that with modern hardware and IDE's and much more complex software where readability is much, Much, MUCH more important. "Code is read much more often than is written". As long as you're not duplicating non-auto-updated code, every keystroke saved is likely to cost exponentially more when someone (even yourself) is trying to read it later.

C#, C# params keyword with examples. In c# params keyword is used to specify a parameter that takes a variable number of arguments. To begin, we use the params keyword on a method that accepts integer values. That method internally sums the values of those integers and returns that value. Params: The params keyword is specified before the array type declaration in a parameter list in a method. Tip: You can use the params keyword on instance or static methods. It must be the

No need to create overload methods, just use one single method with params as shown below

// Call params method with one to four integer constant parameters.
//
int sum0 = addTwoEach();
int sum1 = addTwoEach(1);
int sum2 = addTwoEach(1, 2);
int sum3 = addTwoEach(3, 3, 3);
int sum4 = addTwoEach(2, 2, 2, 2);

C# Params Keyword with Examples, C# params Keyword. Use the params keyword for varargs methods. Params allows a variable number of arguments. Params. This keyword� Why do we use the params keyword in C#? Csharp Programming Server Side Programming While declaring a method, if you are not sure of the number of arguments passed as a parameter, then use the C# param arrays.

C# params Keyword, In C#, params is a keyword which is used to specify a parameter that takes variable number of arguments. It is useful when we don't know the number of� By using the params keyword, you can specify a method parameter that takes a variable number of arguments. The parameter type must be a single-dimensional array. No additional parameters are permitted after the params keyword in a method declaration, and only one params keyword is permitted in a method declaration.

C# Params, In this video we will understand how we can use the params keyword to create dynamic Duration: 6:02 Posted: Oct 19, 2011 Params is an important keyword in C#.It is used as a parameter which can take the variable number of arguments.. Important Point About Params Keyword : It is useful when programmer don’t have any prior knowledge about the number of parameters to be used.

c# (Csharp) :- What is the use of params keyword ? (c# interview , Tip: You can use the params keyword on instance or static methods. It must be the last argument in the parameter list. Static Method C# program that uses params� Why do we use the params keyword in C#? Why do we use modifiers in C/C++? Why do we use restrict qualifier in C++? Why do we use const qualifier in C++? Why do we use comma operator in C#? Why do we use a volatile qualifier in C++? Why do we use interfaces in Java? Why do we use random.seed() in Python? Why do we use extern "C" in C++ code? Why

Comments
  • The code of the method itself will still work perfectly... the calling code may well not...
  • params key word means OPTIONAL parameters that can be passed or not to the Method. An array with out params key word means you MUST pass array argument to the method.
  • Python language implements the same concept so sweetly with an asterisk(*) prefixed parameter as mentioned here.
  • @Ken: You might need to import the System.Linq namespace :)
  • Or return args.Sum(i => i + 2);
  • The sum with a delegate, though, does increase the complexity of the compiled code, which could potentially be less performant. Not really relevant in this particular situation, as it would not result in any closures, but it's worth knowing what the compiler's actually doing to make the best choice.
  • You could also use return args.Select(x => x + 2).Sum();
  • When you add params you lock yourself out of adding additional method arguments without breaking your callers or method resolution.
  • actually an array can be empty. new int[0]. hope this helps! :)
  • I don't understand. Why can't you just enforce that there be at least one? Even without params there's nothing to stop you from passing null or new object[0] as the argument.