Is there a .NET function to remove the first (and only the first) occurrence at the start of a string?

Question

I was using the TrimStart function to do the following:

var example = "Savings:Save 20% on this stuff";
example = example.TrimStart("Savings:".ToCharArray());

I was expecting this to result in example having a value of "Save 20% on this stuff".

However, what I got was "e 20% on this stuff".

After reading the documentation on TrimStart I understand why, but now I'm left wondering if there is a function in .NET that does what I was trying to do in the first place?

Does anyone know of a function so I don't have to create my own and keep track of it?

Answer 1

I don't think such a method exists but you can easily do it using StartsWith and Substring:

s = s.StartsWith(toRemove) ? s.Substring(toRemove.Length) : s;

You can even add it as an extension method:

public static class StringExtension
{
    public static string RemoveFromStart(this string s, string toRemove)
    {
        if (s == null)
        {
            throw new ArgumentNullException("s");
        }

        if (toRemove == null)
        {
            throw new ArgumentNullException("toRemove");
        }

        if (!s.StartsWith(toRemove))
        {
            return s;
        }

        return s.Substring(toRemove.Length);
    }
}

Answer 2

No, I don't believe there's anything which does this built into the framework. It's a somewhat unusual requirement, IMO.

Note that you should think carefully about whether you're trying to remove "the first occurrence" or remove the occurrence at the start of the string, if there is one. For example, think what you'd want to do with: "Hello. Savings: Save 20% on this stuff".

Answer 3

You can do that quite easily using a regular expression.

Remove the occurence on the beginning of the string:

exmaple = Regex.Replace(example, @"^Savings:", "");

Remove the first occurence in the string:

exmaple = Regex.Replace(example, @"(?<!Savings:.*)Savings:", "");