Multiplying strings in C#

Question

Possible Duplicate:
Can I "multiply" a string (in C#)?

In Python I can do this:

>>> i = 3
>>> 'hello' * i
'hellohellohello'

How can I multiply strings in C# similarly to in Python? I could easily do it in a for loop but that gets tedious and non-expressive.

Ultimately I'm writing out to console recursively with an indented level being incremented with each call.

parent
    child
    child
    child
        grandchild

And it'd be easiest to just do "\t" * indent.

Write an extension method, so you can do "hello".times(5). (I'd do it in an answer if I knew C#). — Michael Myers, Jun 05 '09 at 20:23
@mmyers adding behavior to default classes is considered harmful — Eric, Jun 05 '09 at 20:24
@Eric: Considered harmful by who? It can be extremely useful. I would have no problem with this. — Jon Skeet, Jun 05 '09 at 20:26
Exact duplicate http://stackoverflow.com/questions/532892/can-i-multiply-a-string-in-c/532912#532912 — Binary Worrier, Jun 05 '09 at 20:27
@Eric: the visibility of an extension method is limited to the declaring namespace of that method, not to all users of the extended type. — Jimmy, Jun 05 '09 at 20:30

score 19 · Accepted Answer · edited May 23 '17 at 12:13

19

There is an extension method for it in this post.

public static string Multiply(this string source, int multiplier)
{
   StringBuilder sb = new StringBuilder(multiplier * source.Length);
   for (int i = 0; i < multiplier; i++)
   {
       sb.Append(source);
   }

   return sb.ToString();
}

string s = "</li></ul>".Multiply(10);

edited May 23 '17 at 12:13

Community

1
1

answered Jun 05 '09 at 20:24

Shane Fulmer

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I'd make multiplier a uint to prevent infinite loops. – Eric Jun 05 '09 at 20:27
Very slick. I'm definitely going to start using this. – Chris Van Opstal Jun 05 '09 at 20:28
If multiplier is negative an exception will be thrown on creating the StringBuilder and the loop wouldn't even run in any case ... – Joey Jun 05 '09 at 20:29
Using a StringBuilder for this is probably overkill, unless the multiplier is generally very large (as in thousands). – technophile Jun 05 '09 at 20:29
From my own testing, using a StringBuilder where you specify the buffer size (as here) breaks even in speed with about 3-4 concatenations. – JulianR Jun 05 '09 at 21:10

score 14 · Answer 2 · edited May 23 '17 at 11:56

14

If you just need a single character you can do:

new string('\t', i)

See this post for more info.

edited May 23 '17 at 11:56

Community

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answered Jun 05 '09 at 20:24

Chris Van Opstal

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This works for my immediate problem so I guess it's the accepted answer. In general though this wouldn't work. :) – Colin Burnett Jun 05 '09 at 20:27
I really think the extension method Shane Fulmer posted is a better solution. I'd mark his response as the answer IMHO. – Chris Van Opstal Jun 05 '09 at 20:30
@Chris, how do I decide then between the better answer for my specific problem that led to this question and a better, more general answer? – Colin Burnett Jun 05 '09 at 20:32
I think Shane Fulmer's answer is a more elegant solution to your specific problem. After you implement it just do "\t".Multiply(i). Not saying I don't appreciate the points :), just think his solution is superior. – Chris Van Opstal Jun 05 '09 at 20:41

score 12 · Answer 3 · answered Jun 05 '09 at 20:32

12

Here's how I do it...

string value = new string(' ',5).Replace(" ","Apple");

answered Jun 05 '09 at 20:32

Zachary

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I made some simple performance tests and found this to be faster than the `StringBuilder` or `string.Join` version. – enzi Feb 07 '11 at 12:42
This solution just made my day! – Sep 11 '20 at 19:27

score 11 · Answer 4 · answered Jun 05 '09 at 20:25

11

There's nothing built-in to the BCL to do this, but a bit of LINQ can accomplish the task easily enough:

var multiplied = string.Join("", Enumerable.Repeat("hello", 5).ToArray());

answered Jun 05 '09 at 20:25

Noldorin

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score 1 · Answer 5 · answered Jun 05 '09 at 20:27

1

int indent = 5;
string s = new string('\t', indent);

answered Jun 05 '09 at 20:27

Larsenal

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score 1 · Answer 6 · answered Jun 05 '09 at 20:28

1

One way of doing this is the following - but it's not that nice.

 String.Join(String.Empty, Enumerable.Repeat("hello", 3).ToArray())

UPDATE

Ahhhh ... I remeber ... for chars ...

 new String('x', 3)

answered Jun 05 '09 at 20:28

Daniel Brückner

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Identical to mine. It's not the most elegant, but at least it's simple. :) – Noldorin Jun 05 '09 at 20:29

score 1 · Answer 7 · edited Mar 27 '18 at 13:05

1

how about with a linq aggregate...

var combined = Enumerable.Repeat("hello", 5).Aggregate("", (agg, current) => agg + current);

edited Mar 27 '18 at 13:05

MSeifert

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answered Jun 05 '09 at 20:29

Scott Ivey

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var combined = Enumerable.Repeat("hello", 5).Aggregate(new StringBuilder(), (agg, current) => agg.Append(current)).ToString(); – sehe Mar 21 '11 at 10:28

score 0 · Answer 8 · answered Jun 05 '09 at 20:22

0

There is no such statement in C#; your best bet is probably your own MultiplyString() function.

answered Jun 05 '09 at 20:22

Aric TenEyck

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score 0 · Answer 9 · answered Jun 05 '09 at 20:27

0

Per mmyers:

public static string times(this string str, int count)
{
  StringBuilder sb = new StringBuilder();
  for(int i=0; i<count; i++) 
  {
    sb.Append(str);
  }
  return sb.ToString();
}

answered Jun 05 '09 at 20:27

John Weldon

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score 0 · Answer 10 · answered Jun 05 '09 at 20:29

0

As long as it's only one character that you want to repeat, there is a String constructor that you can use:

string indentation = new String('\t', indent);

answered Jun 05 '09 at 20:29

Guffa

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score 0 · Answer 11 · answered Jun 05 '09 at 20:40

I don't think that you can extend System.String with an operator overload, but you could make a string wrapper class to do it.

public class StringWrapper
{
    public string Value { get; set; }

    public StringWrapper()
    {
        this.Value = string.Empty;
    }

    public StringWrapper(string value)
    {
        this.Value = value;
    }

    public static StringWrapper operator *(StringWrapper wrapper,
                                           int timesToRepeat)
    {
        StringBuilder builder = new StringBuilder();

        for (int i = 0; i < timesToRepeat; i++)
        {
            builder.Append(wrapper.Value);
        }

        return new StringWrapper(builder.ToString());
    }
}

Then call it like...

var helloTimesThree = new StringWrapper("hello") * 3;

And get the value from...

helloTimesThree.Value;

Of course, the sane thing to do would be to have your function track and pass in the current depth and dump tabs out in a for loop based off of that.

score -1 · Answer 12 · edited Aug 29 '12 at 09:33

-1

if u need string 3 times just do

string x = "hello";

string combined = x + x + x;

edited Aug 29 '12 at 09:33

Lloyd Powell

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answered Jun 05 '09 at 20:42

1

Doesn't scale very nicely does it... – Marc Jun 05 '09 at 21:10

Multiplying strings in C#

12 Answers12