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

Question

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

Answer 1

Do you mean Char.IsLower(ch); ?

Answer 2

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).

Answer 3

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();

Answer 4

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.

Answer 5

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;
        }


    }

Answer 6

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.

Answer 7

Check here @ MSDN.

Answer 8

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.

Answer 9

Please Stop using ToUpper() and ToLower() ! These methods will create a copy of the original string !

you can read my blog post on the subject http://ppetrov.wordpress.com/2008/06/27/dont-use-toupper-or-tolower/

Answer 10

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.