C# Regex - if string only contains a character

Us开发者_Python百科ing C#/Regex, how do I find a string that only contains commas and no alphanumeric (or other non-comma) symbols?

a: ',,,,,,,'  match
b: ',,,,,,#A' no match

[^,]

If that matches, that means a string contains a non-comma character.

A more complete example:

if (!Regex.IsMatch(yourTestString, "[^,]"))
{
    // This string does NOT contain commas
}

This should do it:

var text = ",,,";
Regex.IsMatch(text, @"^,+$");    // true

If I read your question correctly, you want to know if a string contains only commas.

If so, use this regex: ^[,]+$.

This will only match on strings that contain one or more commas and nothing else.

A string of only commas?

Regex.IsMatch(str, @"^,*$");

That will tell you whether or not str consists entirely of commans or not.

I'd suggest that, as a one-char regex will always have to examine each character of its input string in the worst case, a simple for-loop will definitely be more efficient. Something like this will give the exact same effect in less time and space than any equivalent Regex:

private void IsOnlyOneChar(string input, char c)
{
    for (var i = 0; i < input.Length; ++i)
        if (input[i] != c)
            return false;

    return true;
}

Not literally the answer you were looking for, but in my opinion this is your optimal solution.