How do I write a C# method that takes a variable number of arguments?

Question

Is it possible to send a variable number of arguments to a method?

For instance if I want to write a method that would concatenate many string[] objects into one string, but I wanted it to be able to accept arguments without knowing how many I would want to pass in, how would I do this?

That infinite data structure is going to take a while to iterate over... — Kurru
– Kurru, Commented Feb 14, 2011 at 17:46
The title should probably say variable as opposed to infinite. — JohnOpincar
– JohnOpincar, Commented Feb 14, 2011 at 17:49
@JohnOpincar I could have used IEnumerable, and it did cross my mind however in circumstances where I have multiple string[] objects I would have to write code to assign them to an IEnumerable object, so by using the params keyword (thanks for the tip everyone) I save a few lines. — Payson Welch
– Payson Welch, Commented Feb 14, 2011 at 21:01

Reed Copsey · Accepted Answer · 2011-02-14 17:49:47Z

21

You would do this as:

string ConcatString(params string[] arguments)
{
   // Do work here
}

This can be called as:

string result = ConcatString("Foo", "Bar", "Baz");

For details, see params (C# Reference).

FYI - There is already a String.Concat(params object[] args) - it will concatenate any set of objects by calling ToString() on each. So for this specific example, this is probably not really that useful.

edited Feb 14, 2011 at 17:49

answered Feb 14, 2011 at 17:43

Reed Copsey

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Comments

Mark · Accepted Answer · 2011-02-14 17:44:55Z

4

You can easily create a method that takes an arbitrary number of arguments (including zero), using the params keyword:

public static void UseParams(params int[] list)
{
    for (int i = 0; i < list.Length; i++)
        Console.Write(list[i] + " ");
}

You can even pass an array to this method instead of a list of parameters, and the method will work exactly the same.

answered Feb 14, 2011 at 17:44

Mark

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Comments

George Stocker · Accepted Answer · 2011-02-14 17:47:31Z

4

Use the params keyword to do that:

public static string ConvertToOneString(params string[] list) 
{

    string result = String.Empty;
    for ( int i = 0 ; i < list.Length ; i++ )
    {
        result += list[i];
    }
    return result;
}

Usage:

string s = "hello"
string a = "world"
string result = ConvertToOneString(s, a);

edited Feb 14, 2011 at 17:47

answered Feb 14, 2011 at 17:42

George Stocker

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gillyb · Accepted Answer · 2011-02-14 17:44:28Z

3

very easy to do so using params keyword

void ConcatString(params String[] strArray)
{ 
    foreach (String s in strArray)
    {
        // do whatever you want with all the arguments here...
    }
}

answered Feb 14, 2011 at 17:44

gillyb

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Sachin Shanbhag · Accepted Answer · 2011-02-14 17:42:41Z

2

yes, you can use params for that

answered Feb 14, 2011 at 17:42

Sachin Shanbhag

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Jacob · Accepted Answer · 2011-02-14 17:42:53Z

2

Use params:

void YourMethod(params string[] infiniteArgs) { }

answered Feb 14, 2011 at 17:42

Jacob

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Richard Schneider · Accepted Answer · 2011-02-14 20:13:22Z

2

string MyConcat(params string[] values)
{
    var s = new StringBuilder();
    foreach (var v in values)
       s.Append(v);
    return s.ToString();
}

answered Feb 14, 2011 at 20:13

Richard Schneider

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Joe · Accepted Answer · 2011-02-14 17:42:50Z

1

You don't mean infinite (the answer to that question is no) but you do mean 'variable'. Here is your answer (yes): http://blogs.msdn.com/b/csharpfaq/archive/2004/08/05/209384.aspx

answered Feb 14, 2011 at 17:42

Joe

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1 Comment

Joe Over a year ago

Why the downvote? Perhaps the voter didn't see the history of the question. If so, please review and remove the downvote if you want to.

David · Accepted Answer · 2011-02-14 17:42:17Z

0

In practice, infinite - no (there is a finite amount of memory available, for example).

Unknown at design-time, yes.

The classic example of this is how it's handled on a Console application.

http://dotnetperls.com/main

http://msdn.microsoft.com/en-us/library/cb20e19t(VS.71).aspx

answered Feb 14, 2011 at 17:42

David

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