Best way to repeat a character in C#

What about this:

string tabs = new string('\t', n);

Where n is the number of times you want to repeat the string.

Or better:

static string Tabs(int n)
{
    return new string('\t', n);
}

string.Concat(Enumerable.Repeat("ab", 2));

Returns

"abab"

And

string.Concat(Enumerable.Repeat("a", 2));

Returns

"aa"

from...

Is there a built-in function to repeat string or char in .net?

In all versions of .NET, you can repeat a string thus:

public static string Repeat(string value, int count)
{
    return new StringBuilder(value.Length * count).Insert(0, value, count).ToString();
}

To repeat a character, new String('\t', count) is your best bet. See the answer by @CMS.

The best version is certainly to use the builtin way:

string Tabs(int len) { return new string('\t', len); }

Of the other solutions, prefer the easiest; only if this is proving too slow, strive for a more efficient solution.

If you use a StringBuilder and know its resulting length in advance, then also use an appropriate constructor, this is much more efficient because it means that only one time-consuming allocation takes place, and no unnecessary copying of data. Nonsense: of course the above code is more efficient.

Extension methods:

public static string Repeat(this string s, int n)
{
    return new String(Enumerable.Range(0, n).SelectMany(x => s).ToArray());
}

public static string Repeat(this char c, int n)
{
    return new String(c, n);
}