Bug in C# - "FooBar".StartsWith(string.Empty) is true [duplicate]

This question already has answers here: 开发者_运维百科 Closed 11 years ago.

Possible Duplicate:

Why does “abcd”.StartsWith(“”) return true?

Something similar to this being true caught us out:

"FooBar".StartsWith(string.Empty)

Firstly I don't think it should be true but I am also not quite sure why it is true, looking at the "Reflector'ed" code:

public bool StartsWith(string value, bool ignoreCase, CultureInfo culture)
{
    if (value == null)
    {
        throw new ArgumentNullException("value");
    }
    if (this == value)
    {
        return true;
    }
    CultureInfo info = (culture == null) ? CultureInfo.CurrentCulture : culture;
    return info.CompareInfo.IsPrefix(this, value, ignoreCase ? CompareOptions.IgnoreCase : CompareOptions.None);
}

ignoreCase is false and culture is null. So why does "this == value" evaluate to true?

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It's not that this == value returns true, but CompareInfo.IsPrefix is documented as returning true for String.Empty:

Every string starts and ends with an empty substring (""); therefore, if prefix is an empty string, this method returns true.

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Why do you think "this == value" evaluate to true? I believe this behavior is correct. Any string may be considered to be starting with empty string.

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Actually FooBar starts with string.Empty. Any string can be considered starting with string.Empty, as well as 0+a = a.