# What is the “correct” way to replace from a list chars in a string?

Often I need to clean a file name using Path.GetInvalidFileNameChars(), however I do not know of a way to search for any of the invalid letters (except by using Regex) in one pass.

public string LoopMethod()
{
StringBuilder sb = new StringBuilder(fileName);
foreach(var invalidChar in Path.GetInvalidFileNameChars())
{
sb.Replace(invalidChar, '_');
}
return sb.ToString();
}

Regex invalidCharsRegex;
public void RegexMethodInit()
{
var invalidChars = Path.GetInvalidPathChars().Select(c => Regex.Escape(c.ToString())).ToString();
invalidCharsRegex = new Regex(string.Join("|", invalidChars));
}

public string RegexMethod(string fileName)
{
return invalidCharsRegex.Replace(fileName, "_");
}


Is one of those ways the "correct" way to to this or is there a better function I am missing?

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Related: forums.asp.net/t/1185961.aspx/1 –  Rice Flour Cookies Feb 21 '13 at 23:28
@Leonid Path.GetInvalidPathChars() returns a char[] of characters that are illegal in a file name. What I wanted to know is what is the proper way to clean a filename from the returned char[], is it to just loop like in my example, or is there a function that can take in a char[] and replace on a string in one operation? –  Scott Chamberlain Feb 22 '13 at 0:11

foreach(var c in Path.GetInvalidPathChars())

var chars = Path.GetInvalidPathChars()