How do I convert a single char to a string?

Question

I'd like to enumerate a string and instead of it returning chars I'd like to have the iterative variable be of type string. This probably isn't possible to have the iterative type be a string so what is the most efficient way to iterate through this string?

Do I need to create a new string object with each iteration of the loop or can I perform a cast somehow?

String myString = "Hello, World";
foreach (Char c in myString)
{
    // what I want to do in here is get a string representation of c
    // but I can't cast expression of type 'char' to type 'string'
    String cString = (String)c; // this will not compile
}

Stereoscope

Answer 1

Use the .ToString() Method

String myString = "Hello, World";
foreach (Char c in myString)
{
    String cString = c.ToString(); 
}

Ladylove

Consider using the C# types string and char instead of the CLR types. The same in the end but arguably more correct in C#. – Omeara

@Omeara You are right, I just modified OP's example code to show the ToString Method. – Ladylove

The comment was directed at him, not you. No worries. – Omeara

This is all well and good, but why doesn't this work? No one seems to explain this. – Mandrake

@druciferre What do you mean by why doesn't this work? It works fine for me. – Menard

@tom_mai78101, honestly I have no idea why I asked that. It was over a year ago. I suspect the answer has been modified and because other comments deleted. – Mandrake

@druciferre This answer has not been modified since I made it in 2012. – Ladylove

Best guess is someone commented "this doesn't work" and their comment has since been deleted. – Mandrake

@tom_mai78101, looking over the question again I think I was complaining none of the answers explain why casting a char to a string doesn't work or apparently compile. – Mandrake

@druciferre Oh I see. There is no implicit conversion from anything to char in .NET, and vice versa I guess. – Menard

I think the question @druciferre was asking is why (or rather, how) using C# types versus CLR types is "more correct." That's what I'm wondering, anyway! – Haemoglobin

Seems to work, but why can't we just use the built-in syntactic way to do explicit conversions? e.g. string s = (string) c – Wee

Interestingly, VB freely allows you to assign a Char to a String variable. Behind-the-scenes it uses Microsoft.VisualBasic.CompilerServices.Conversions.ToString, but the VB syntax supports it in an intuitive manner. – Widescreen

(I'd guess that char is a value type and string is a reference type, so that's why you can't easily turn a char into a string in C#) – Widescreen

@Omeara Jeffrey Richter recommends using the CLR type name rather than the C# keyword in his book "CLR Via C#". Some reasons why: the names are more descriptive (consider Int64 and Int32 vs long and int). You can use the CLR type name in all languages that target .NET, the same is not necessarily true for C# keywords. – Winer

@DavidKlempfner In the same way, one can argue in favor of code analysis: "Use language keywords instead of framework type names for type references (IDE0049)". In the end it's an option. The default is to prefer the language keyword. Personally, I put more weight to the default of the rule, than someone's opinion. – Injury

@Injury IDE0049 doesn't provide an explanation as to why that way is better, it just says "do it". Jeffrey Richter, who btw is not just "someone" but was the lead consultant for building the .NET Framework, provides reasons as to why using the CLR type name is better. – Winer

The reasons of the referenced person, which are fine BTW, still amounts to an opinion. One may agree or not. As to my favoring the default rule choice, is that it was likely chosen over time, and by more than a single person, also involved and with reasons. – Injury

Answer 2

You have two options. Create a string object or call ToString method.

String cString = c.ToString();
String cString2 = new String(c, 1); // second parameter indicates
                                    // how many times it should be repeated

Nitaniter

Answer 3

With C# 6 interpolation:

char ch = 'A';
string s = $"{ch}";

This shaves a few bytes. :)

Driving

String interpolation efficiency is costly though. Better to just do new String(ch,1). – Basinet

Answer 4

It seems that the obvious thing to do is this:

String cString = c.ToString()

Stereoscope

Answer 5

Create a new string from the char.

 String cString = new String(new char[] { c });

or

 String cString = c.ToString();

Dose

Answer 6

I recently wanted to know which approach was the fastest, so I benchmarked 5 approaches.

The answer is that you should use new String(myChar,1), for the fastest times:

|           Method |      Mean |    Error |    StdDev | Rank |   Gen0 | Allocated |
|----------------- |----------:|---------:|----------:|-----:|-------:|----------:|
|        NewString |  10.65 ns | 0.502 ns |  1.473 ns |    1 | 0.0031 |      16 B |
|        AddString |  11.83 ns | 0.845 ns |  2.466 ns |    2 | 0.0030 |      16 B |
|     CharToString |  12.26 ns | 0.662 ns |  1.951 ns |    2 | 0.0030 |      16 B |
| NewStringPointer |  33.03 ns | 1.382 ns |  3.988 ns |    3 | 0.0030 |      16 B |
|      Interpolate | 119.31 ns | 5.351 ns | 15.525 ns |    4 | 0.0083 |      44 B |

Where the 5 methods are:

public string CharToString(char input) => input.ToString();
public string Interpolate(char input) => $"{input}";
public string AddString(char input) => input + "";
public string NewString(char input) => new String(input,1);
public string NewStringPointer(char input)
{
    unsafe
    {
        return new String(& input);
    }
}

Belittle

Can you also test having a table of 256 strings (1 for each char) then copying one of them to get a new one? (maybe like cloning if its read-only use or deep copying if its write+read?) – Chanachance

@huseyintugrulbuyukisik what do you think you're referring to w.r.t. cloning, and read-only/read-write? None of those concepts are even slightly applicable to strings. – Belittle

Like a singleton with a string field and changing its field depending on use case. – Chanachance

??? I don't have the faintest idea what you're talking about. But this benchmarking is pretty trivial to run; feel free to go and try it yourself :) Search Nick Chapsas Benchmark.NET – Belittle

Answer 7

Create an extension method:

public static IEnumerable<string> GetCharsAsStrings(this string value)
{
    return value.Select(c =>
           {
                //not good at all, but also a working variant
                //return string.Concat(c);

                return c.ToString();
           });
}

and loop through strings:

string s = "123456";
foreach (string c in s.GetCharsAsStrings())
{
    //...
}

Lidstone

Answer 8

you can use + with empty string "", please check the below code:

char a = 'A';
//a_str is a string, the value of which is "A".
string a_str = ""+a;

Suppuration

Looks like (ugly) javascript code – Madge

Answer 9

Did you try:

String s = new String(new char[] { 'c' });

Amby

There is no ctor that takes just char – Nitaniter

Answer 10

String cString = c.ToString();

Lymphosarcoma

Answer 11

Why not this code? Won't it be faster?

string myString = "Hello, World";
foreach( char c in myString )
{
    string cString = new string( c, 1 );
}

Distraint

Answer 12

probably isn't possible to have the iterative type be a string

Sure it is:

foreach (string str in myString.Select(c => c.ToString())
{
...
}

Any of the suggestions in the other answers can be substituted for c.ToString(). Probably the most efficient by a small hair is c => new string(c, 1), which is what char.ToString() probably does under the hood.

Sheol