Convert String To camelCase from TitleCase C#

Question

I have a string that I converted to a TextInfo.ToTitleCase and removed the underscores and joined the string together. Now I need to change the first and only the first character in the string to lower case and for some reason, I can not figure out how to accomplish it. Thanks in advance for the help.

class Program
{
    static void Main(string[] args)
    {
        string functionName = "zebulans_nightmare";
        TextInfo txtInfo = new CultureInfo("en-us", false).TextInfo;
        functionName = txtInfo.ToTitleCase(functionName).Replace('_', ' ').Replace(" ", String.Empty);
        Console.Out.WriteLine(functionName);
        Console.ReadLine();
    }
}

Results: ZebulansNightmare

Desired Results: zebulansNightmare

UPDATE:

class Program
{
    static void Main(string[] args)
    {
        string functionName = "zebulans_nightmare";
        TextInfo txtInfo = new CultureInfo("en-us", false).TextInfo;
        functionName = txtInfo.ToTitleCase(functionName).Replace("_", string.Empty).Replace(" ", string.Empty);
        functionName = $"{functionName.First().ToString().ToLowerInvariant()}{functionName.Substring(1)}";
        Console.Out.WriteLine(functionName);
        Console.ReadLine();
    }
}

Produces the desired output

Solution 1

You just need to lower the first char in the array. See this answer

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

As a side note, seeing as you are removing spaces you can replace the underscore with an empty string.

.Replace("_", string.Empty)

Solution 2

Implemented Bronumski's answer in an extension method (without replacing underscores).

 public static class StringExtension
 {
     public static string ToCamelCase(this string str)
     {                    
         if(!string.IsNullOrEmpty(str) && str.Length > 1)
         {
             return char.ToLowerInvariant(str[0]) + str.Substring(1);
         }
         return str.ToLowerInvariant();
     }
 }
 //Or
 public static class StringExtension
 {
     public static string ToCamelCase(this string str) =>
         string.IsNullOrEmpty(str) || str.Length < 2
         ? str.ToLowerInvariant()
         : char.ToLowerInvariant(str[0]) + str.Substring(1);
 }

and to use it:

string input = "ZebulansNightmare";
string output = input.ToCamelCase();

Solution 3

If you're using .NET Core 3 or .NET 5, you can call:

System.Text.Json.JsonNamingPolicy.CamelCase.ConvertName(someString)

Then you'll definitely get the same results as ASP.NET's own JSON serializer.

Solution 4

Here is my code, in case it is useful to anyone

    // This converts to camel case
    // Location_ID => locationId, and testLEFTSide => testLeftSide
    static string CamelCase(string s)
    {
        var x = s.Replace("_", "");
        if (x.Length == 0) return "null";
        x = Regex.Replace(x, "([A-Z])([A-Z]+)($|[A-Z])",
            m => m.Groups[1].Value + m.Groups[2].Value.ToLower() + m.Groups[3].Value);
        return char.ToLower(x[0]) + x.Substring(1);
    }

If you prefer Pascal-case use:

    static string PascalCase(string s)
    {
        var x = CamelCase(s);
        return char.ToUpper(x[0]) + x.Substring(1);
    }

Solution 5

The following code works with acronyms as well. If it is the first word it converts the acronym to lower case (e.g., VATReturn to vatReturn), and otherwise leaves it as it is (e.g., ExcludedVAT to excludedVAT).

name = Regex.Replace(name, @"([A-Z])([A-Z]+|[a-z0-9_]+)($|[A-Z]\w*)",
            m =>
            {
                return m.Groups[1].Value.ToLower() + m.Groups[2].Value.ToLower() + m.Groups[3].Value;
            });

View more solutions

Comments

[StayOnTarget]

You should just post your own answer instead of putting a solution in the question, its a little more confusing this way.

[Gabriel_W]

Thanks just what I needed.

[Gabriel_W]

Good call. Made the adjustments and updated the question.

[Rick M.]

Welcome to StackOverflow! Although this might answer the question, consider adding text to why this is a suitable answer and links to support your answer!

[Diogo Luis]

The only issue I see is if the string is just a "A". It should return "a", right?

[Muster Station]

Finally an example that converts MYCase to myCase, instead of mYCase. Thanks!

[s1cart3r]

Given that no other answer has an essay supporting the answer and only one has a link I think this a bit harsh, or very "StackOverflow-ish". The first answer Kenny gave was a good anser imo (although I agree there is a typo in te to text).

[CodeWarrior]

That was harsh?

[Rhys van der Waerden]

This is good, but unfortunately it will convert PascalCase into Pascalcase.

[Mojtaba]

That doesn't work with acronyms in the beginning (e.g., VATReturnAmount). See my answer.

[ygoe]

@MusterStation But why? Shouldn't you just have "MyCase" in the first place? If "Y" is uppercase, then it's probably another word, right?

[ygoe]

@CodeWarrior No, it wasn't. He could have said "please" though. BTW, the code style looks ugly (probably not just to me), hard to read.

[John Henckel]

@ygoe maybe. in "MYCase" perhaps M is a word, Y is a word, and Case is a word. However, it is more likely that "MY" is a two letter acronym. For example "innerHTML" is two words, not five.

[Klaus Gütter]

While this might answer the question, it would be much more helpful if you explain your code a bit.

[Legacy Code]

Sorry but this is not a good code at all... Concatenating strings create new strings... In this case you are creating as many strings as your original string in str. If you have a long string, the GC will hate you.

[Tushee]

Agreed with @Mojtaba. DON'T use this if you want to have compatibility with camelCase JSON serialization in ASP.NET. Acronyms at the beginning won't come out the same.

[Tushee]

This converts to PascalCase not camelCase

[John Henckel]

@CraigShearer yes.... the last line can be ToLower if you want camelCase.

[NibblyPig]

Thank you, this is much better. It matches the behaviour of MVC when you return Json(new { CAPSItem = ... } whereas the accepted answer will create a mismatch

[HappyNomad]

A problem with acronyms arises if you must convert from camelCase back to PascalCase. For example, I don't see how to convert vatReturn back to VATReturn. Better to use VatReturn as your pascal naming convention, then you can stick to just modifying the first letter.

[Mojtaba]

@HappyNomad although your point is valid in its context, the question is about converting to camelCase; that means using VatReturn instead of vatReturn for acronyms is not an answer for this question.

[Joep Beusenberg]

Why is your function called CamelCase while it actually converts to PascalCase? :)

[Joep Beusenberg]

Most of all it doesn't even answer the question. It converts to TitleCase, which was not the question asked.

[John Henckel]

@JoepBeusenberg ok i fixed it

[AussieJoe]

this did not work for me, it converted everything to lower case in my situation

[Sras]

this is quite strange forward answer. you just create JsonSerilizerSetting by setting its contractresovler option to Camelcase. So, the object, is anything you want to serilize, together wtih the setting. you can customize any setting you wish to

[Filipe Piletti Plucenio]

Please, add some description or comments for help them.

[Dave]

Just to note, this does not remove spaces so you need to do JsonNamingPolicy.CamelCase.ConvertName(str).Replace(" ", string.Empty)

[Matthew M.]

In .NET Core C#9 you can make it even more concise: return char.ToLowerInvariant(s[0]) + s[1..];

[Cameron MacFarland]

To fix the "InnerHTMLExample" change the regex to "(^[A-Z])([A-Z]+)($|[A-Z])"