First Character of String Lowercase - C#

Question

How can I make the first character of a string lowercase?

For example: ConfigService

And I need it to be like this: configService

Did you check this out? http://stackoverflow.com/questions/3565015/bestpractice-transform-first-character-of-a-string-into-lower-case — Niklas, Feb 13 '14 at 13:34
http://stackoverflow.com/questions/4135317/make-first-letter-of-a-string-upper-case Instead `ToUpper` change it to `ToLower`. — Random, Feb 13 '14 at 13:35
Note: anything "first character" related will be very dangerous when talking about anything outside simple unicode. Combining diacritics, conjugate pairs, and right-to-left will all cause it problems — Marc Gravell, Feb 13 '14 at 13:37

score 57 · Accepted Answer · edited Apr 09 '22 at 05:02

57

This will work:

public static string? FirstCharToLowerCase(this string? str)
{
    if ( !string.IsNullOrEmpty(str) && char.IsUpper(str[0]))
        return str.Length == 1 ? char.ToLower(str[0]).ToString() : char.ToLower(str[0]) + str[1..];

    return str;
}

(This code arranged as "C# Extension method")

Usage:

myString = myString.FirstCharToLowerCase();

edited Apr 09 '22 at 05:02

Tono Nam

34,064
78
298
470

answered Feb 13 '14 at 13:40

Amit Joki

58,320
7
77
95

2

Don't forget to check for empty strings. – nima Feb 13 '14 at 15:04
6

And strings that only contains one character. – Crono Feb 13 '14 at 15:22
Note: `char.IsLower(str[0])` check is not required, but may speed up an execution. – Evgeny Nozdrev Mar 19 '21 at 16:50
why the [CanBeNull] is not supported in ASp net core. – Sayed Muhammad Idrees Feb 11 '22 at 16:40
[CanBeNull] used to be supported but the new convention is to add a ? after the string. I made an edit to this question cause of this. – Tono Nam Apr 09 '22 at 04:02
The method can be made way simpeler anno 2022: `return string.IsNullOrEmpty(str) ? str : char.ToLower(str[0]) + str[1..];` – Rich_Rich Dec 13 '22 at 16:12

Tim Schmelter · Answer 2 · 2020-12-27T02:52:55.850

21

One way:

string newString = oldString;
if (!String.IsNullOrEmpty(newString))
    newString = Char.ToLower(newString[0]) + newString.Substring(1);

For what it's worth, an extension method:

public static string ToLowerFirstChar(this string input)
{
    if(string.IsNullOrEmpty(input))
        return input;

    return char.ToLower(input[0]) + input.Substring(1);
}

Usage:

string newString = "ConfigService".ToLowerFirstChar(); // configService

edited Dec 27 '20 at 02:52

answered Feb 13 '14 at 13:35

Tim Schmelter

450,073
74
686
939

Does this work well with DBCS? – Thorsten Dittmar Feb 13 '14 at 13:35
2

@ThorstenDittmar .NET has Unicode strings. And char represents UTF-16 character – Sergey Berezovskiy Feb 13 '14 at 13:39
1

@SergeyBerezovskiy Correct. The same question applies to surrogate pairs, though, which would not be handled correctly (and just don't get handled correctly in general, in most code I've seen). – Feb 13 '14 at 13:40
2

@AmitJoki In that case, `Char.ToLower` returns the original character, so the string remains unchanged. – Feb 13 '14 at 13:43
1

@AmitJoki That is because you are printing out `s` and not `newString` – Andrew Backes Feb 13 '14 at 13:47
@AmitJoki: the check is redundant. However, i have shown an extension which makes it clearer. Was that the reason for the downvote or have i missed something else? – Tim Schmelter Feb 13 '14 at 13:48
Sorry @TimSchmelter It was my mistake – Amit Joki Feb 13 '14 at 13:49
I don't know the reason, why my answer was marked as answer :) Thought this post will be marked as answer – Amit Joki Feb 13 '14 at 13:51
1

@SergeyBerezovskiy I see. I didn't actually know that :-) – Thorsten Dittmar Feb 13 '14 at 13:54

score 8 · Answer 3 · answered Feb 13 '14 at 13:35

8

You could try this:

lower = source.Substring(0, 1).ToLower() + source.Substring(1);

answered Feb 13 '14 at 13:35

Thorsten Dittmar

55,956
8
91
139

score 2 · Answer 4 · answered Feb 13 '14 at 13:36

2

    string FirstLower(string s)
    {
        if(string.IsNullOrEmpty(s))
            return s;
        return s[0].ToString().ToLower() + s.Substring(1);
    }

answered Feb 13 '14 at 13:36

nima

6,566
4
45
57

score 2 · Answer 5 · answered Feb 13 '14 at 13:42

Use this function:

public string GetStringWithFirstCharLowerCase(string value)
{
    if (value == null) throw new ArgumentNullException("value")
    if (String.IsNullOrWhiteSpace(value)) return value;

    char firstChar = Char.ToLowerInvariant(value[0]);

    if (value.Length == 1) return firstChar;

    return firstChar + value.Substring(1);
}

Please note that further overloading will be necessary if support for other languages is required.

score 2 · Answer 6 · answered Feb 13 '14 at 13:52

    public static string Upper_To_Lower(string text)
    {
        if (Char.IsUpper(text[0]) == true) { text = text.Replace(text[0], char.ToLower(text[0])); return text; }

        return text;
    }

    public static string Lower_To_Upper(string text)
    {
        if (Char.IsLower(text[0]) == true) { text = text.Replace(text[0], char.ToUpper(text[0])); return text; }

        return text;
    }

Hope this will help you ! here i made two methods taking as parameter any string and return the string with the first letter uppercase or lowercase according to the method you will use

score 1 · Answer 7 · answered Feb 13 '14 at 13:35

1

string test = "ConfigService";
string result = test.Substring(0, 1).ToLower() + test.Substring(1);

answered Feb 13 '14 at 13:35

ken2k

48,145
10
116
176

2

Also, using `Substring` method just for getting first char seems a little bit over the top :) – Tarec Feb 13 '14 at 13:38

score 1 · Answer 8 · edited May 23 '17 at 12:09

1

I would simply do this:

Char.ToLowerInvariant(yourstring[0]) + yourstring.Substring(1)

Simple and gets the job done.

EDIT:

Looks like this thread had the same idea. :)

edited May 23 '17 at 12:09

Community

1
1

answered Feb 13 '14 at 13:36

Andrew Backes

1,884
4
21
37

terrybozzio · Answer 9 · 2014-02-13T13:56:13.907

1

This can help you,changes first character to lower if it is upper and also checks for null or empty and only whitespace string:

string str = "ConfigService";
string strResult = !string.IsNullOrWhiteSpace(str) && char.IsUpper(str, 0) ? str.Replace(str[0],char.ToLower(str[0])) : str;

edited Feb 13 '14 at 13:56

answered Feb 13 '14 at 13:50

terrybozzio

4,424
1
19
25

First Character of String Lowercase - C#

9 Answers9