Compareinfo.lastindexof problem with ignoresymbols and symbol

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Whenever "IgnoreSymbols" is looking for ":" the return is = 5. Why?

C#

// OK. Returns 3.
int Pos = System.Globalization.CultureInfo.CurrentCulture.CompareInfo.LastIndexOf("AAA:AA", ":", System.Globalization.CompareOptions.IgnoreCase);

// OK. Returns 3.
Pos = System.Globalization.CultureInfo.CurrentCulture.CompareInfo.LastIndexOf("AAA:AA", ":", System.Globalization.CompareOptions.IgnoreNonSpace);

// BAD. Returns 5.
Pos = System.Globalization.CultureInfo.CurrentCulture.CompareInfo.LastIndexOf("AAA:AA", ":", System.Globalization.CompareOptions.IgnoreSymbols);

// OK. Returns 3.
Pos = System.Globalization.CultureInfo.CurrentCulture.CompareInfo.LastIndexOf("AAABAA", "B", System.Globalization.CompareOptions.IgnoreSymbols);

// OK. Returns 3.
Pos = System.Globalization.CultureInfo.CurrentCulture.CompareInfo.LastIndexOf("AAA:AA", ":", System.Globalization.CompareOptions.IgnoreCase | System.Globalization.CompareOptions.IgnoreNonSpace);

// BAD. Returns 5.
Pos = System.Globalization.CultureInfo.CurrentCulture.CompareInfo.LastIndexOf("AAA:AA", ":", System.Globalization.CompareOptions.IgnoreCase | System.Globalization.CompareOptions.IgnoreNonSpace | System.Globalization.CompareOptions.IgnoreSymbols);

What I have tried:

in all the sites of internet.in all the sites of internet.

Posted 19-Sep-19 20:30pm

zequion

Updated 20-Sep-19 3:45am

Maciej Los

v2

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2 solutions

Solution 2

If you know what the problem of the count parameter is, I also appreciate it.

Posted 20-Sep-19 3:45am

zequion

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Richard Deeming · Accepted Answer · 2019-09-20T03:01:00

The documentation[^] is a little confusing - the overload you're calling simply says that it returns the index of the character, if found, or -1 otherwise.

However, looking at the other overloads, they include the additional information:
"Returns startIndex if value is an ignorable character."

Looking at the source of the overload you're calling[^], you can see it simply calls the other overload, passing in source.Length - 1 as the startIndex.

Since the value you're looking for is an ignorable character, the method therefore returns source.Length - 1 - ie: 5.

This seems like an odd implementation choice to me. I'd expect it to return -1 in this case. But it is at least correct according to the documentation. :)