Is there a built-in IsLowerCase() in .NET?

Question

Is there a built-in IsLowerCase() in .NET?

The implementation's only trivial until you need to consider other locales... — Roger Lipscombe, Dec 23 '08 at 15:19

score 7 · Answer 1 · answered Dec 23 '08 at 15:29

public static bool IsLowerCase( this string text ) {
    if ( string.IsNullOrEmpty( text ) ) { return true; }
    foreach ( char c in text )
        if ( char.IsLetter( c ) && !char.IsLower( c ) )
            return false;

    return true;
}


"someString".IsLowerCase();

score 6 · Accepted Answer · answered Dec 23 '08 at 15:19

6

Do you mean Char.IsLower(ch); ?

answered Dec 23 '08 at 15:19

Gant

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Jay Bazuzi · Answer 3 · 2008-12-24T01:08:55.763

3

Keep in mind that localization makes this a non-trivial question. The first example is fine as long as you don't care:

string s = ...
s.All(c => char.IsLower(c));

If you do care, do it this way:

s.ToLower(CultureInfo.CurrentUICulture) == s;

This gives you the chance to address culture issues.

edited Dec 24 '08 at 01:08

answered Dec 23 '08 at 15:55

Jay Bazuzi

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Why not s.All(c => char.IsLower(c))? – dalle Dec 23 '08 at 16:29
dalle: You need to do a String.ToCharArray() before you can do lambda expressions on characters. That is, bool isStringLower = str.ToCharArray().All(c => char.IsLower(c)); – Tamas Czinege Dec 23 '08 at 16:35
@DrJokepu: Actually, you don't need to do ToCharArray() before you can do the lambda - I just tested it, it works fine on a string too... – BenAlabaster Dec 23 '08 at 17:43
@DrJokepu: According to http://msdn.microsoft.com/en-us/library/system.string_members.aspx#extensionMethodTableToggle you don't need it. – dalle Dec 24 '08 at 00:02
Ahh, I think IntelliSense just supresses them on string. I'll modify my answer. – Jay Bazuzi Dec 24 '08 at 01:08

George Stocker · Answer 4 · 2008-12-23T15:26:02.697

Edit: Didn't see the actual meaning of your question. You could use:

char.IsLower(c);

As far as easily converting between cases:

Sure is:

MSDN says:

 string upper = "CONVERTED FROM UPPERCASE";
 Console.WriteLine(upper.ToLower());

It's part of the string class.

There's also the TextInfo class:

CultureInfo cultureInfo   = Thread.CurrentThread.CurrentCulture;
TextInfo textInfo = cultureInfo.TextInfo;

Console.WriteLine(textInfo.ToTitleCase(title));
Console.WriteLine(textInfo.ToLower(title));
Console.WriteLine(textInfo.ToUpper(title));

Which allows for more variation to change caps and whatnot (like ToTitleCase).

I think what he is asking is if there is a function that identifies a lower case string — Sergio, Dec 23 '08 at 15:33

BenAlabaster · Answer 5 · 2008-12-23T17:41:15.013

As others have mentioned you can easily do this for a single char using char.IsLower(ch)

But to extend the String primitive, it wouldn't be very difficult. You can extend the BCL relatively simply using the Runtime.CompilerServices namespace:

Imports System.Runtime.CompilerServices
Module CustomExtensions

    <Extension()> _
    Public Function IsLowerCase(ByVal Input As String) As Boolean
        Return Return Input.All(Function(c) Char.IsLower(c))
    End Function

End Module

Or in C#, that would be:

using System.Runtime.CompilerServices; 
static class CustomExtensions 
{ 
    public static bool IsLowerCase(this string Input) 
    { 
        return Input.All(c => char.IsLower(c)); 
    }
}

Now you can figure it out using:

Console.WriteLine("ThisIsMyTestString".IsLowerCase())

Which would return false because there are upper case characters contained within the string.

simply "return Input.All(c => char.IsLower(c))" is enough, and faster since it can return as soon as it finds the first upper case letter. — Lucas, Dec 23 '08 at 16:11
Ah, nice...I never noticed you could do an All on a String object... thanks. — BenAlabaster, Dec 23 '08 at 17:40

score 0 · Answer 6 · answered Dec 23 '08 at 15:47

0

How about:

public bool IsLower(string TestString)
    {
        if (String.IsNullOrEmpty(TestString))
        {
            return true;
        }

        string testlower = TestString.ToLowerInvariant();

        if (String.Compare(TestString, testlower, false) == 0)
        {
            return true;
        }
        else
        {
            return false;
        }


    }

answered Dec 23 '08 at 15:47

Stever B

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Long windedness is intentional in this case. And yeah, i think asd234as!!!df is lower case. 2,3,4 and ! by definition don't have case at all so are both lower and upper case. – Stever B Dec 23 '08 at 16:51

score 0 · Answer 7 · answered Dec 23 '08 at 15:58

0

balabaster, please do not use this approach with FindAll/Count. All you need is

return Input.ToList().Exists(c => Char.IsUpper(c));

It will stop the iteration on the first upper case character.FindAll create a new List and you use only the Count property. If we have a long string that's in upper case, you will end up with a copy of the original string.

answered Dec 23 '08 at 15:58

Petar Petrov

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@Petrov: .All (as I have used) drops out on the first existence of a non-lowercase character. What you've suggested is equally long winded. If you drop the ToList().Exists() and use instead just .All(c => char.IsLower(c)) then you get even better results! – BenAlabaster Dec 23 '08 at 17:48

score -1 · Answer 8 · answered Dec 23 '08 at 16:16

-1

Guys why this LINQ abuse (ToList(), ToArray(), All(), Any(), ...) ? I love LINQ and lambdas too but in this case I think the good old foreach is what we need. See the answer of TcKs as reference - but we can do better if we remove the superfluous

char.IsLetter( c )

because IsLower() is doing the same check.

answered Dec 23 '08 at 16:16

Petar Petrov

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Because a nice .All(c => Char.IsLower(c)) takes care of the whole lot... forget iterating over a collection - just query it like you would a table in a database. Much more elegant... – BenAlabaster Dec 23 '08 at 17:46

Is there a built-in IsLowerCase() in .NET?

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