Convert char to int in C#

Question

I have a char in c#:

char foo = \'2\';

Now I want to get the 2 into an int. I find that Convert.ToInt32 returns the actual decimal value o

Answer 1

char c = '1';
int i = (int)(c-'0');

and you can create a static method out of it:

static int ToInt(this char c)
{
    return (int)(c - '0');
}

Answer 2

Comparison of some of the methods based on the result when the character is not an ASCII digit:

char c1 = (char)('0' - 1), c2 = (char)('9' + 1); 

Debug.Print($"{c1 & 15}, {c2 & 15}");                                   // 15, 10
Debug.Print($"{c1 ^ '0'}, {c2 ^ '0'}");                                 // 31, 10
Debug.Print($"{c1 - '0'}, {c2 - '0'}");                                 // -1, 10
Debug.Print($"{(uint)c1 - '0'}, {(uint)c2 - '0'}");                     // 4294967295, 10
Debug.Print($"{char.GetNumericValue(c1)}, {char.GetNumericValue(c2)}"); // -1, -1

Answer 3

Interesting answers but the docs say differently:

Use the GetNumericValue methods to convert a Char object that represents a number to a numeric value type. Use Parse and TryParse to convert a character in a string into a Char object. Use ToString to convert a Char object to a String object.

http://msdn.microsoft.com/en-us/library/system.char.aspx

Answer 4

This worked for me:

int bar = int.Parse("" + foo);

Answer 5

Principle:

char foo = '2';
int bar = foo & 15;

The binary of the ASCII charecters 0-9 is:

0   -   0011 0000
1   -   0011 0001
2   -   0011 0010
3   -   0011 0011
4   -   0011 0100
5   -   0011 0101
6   -   0011 0110
7   -   0011 0111
8   -   0011 1000
9   -   0011 1001

and if you take in each one of them the first 4 LSB (using bitwise AND with 8'b00001111 that equals to 15) you get the actual number (0000 = 0,0001=1,0010=2,... )

Usage:

public static int CharToInt(char c)
{
    return 0b0000_1111 & (byte) c;
}

Answer 6

I'm using Compact Framework 3.5, and not has a "char.Parse" method. I think is not bad to use the Convert class. (See CLR via C#, Jeffrey Richter)

char letterA = Convert.ToChar(65);
Console.WriteLine(letterA);
letterA = 'あ';
ushort valueA = Convert.ToUInt16(letterA);
Console.WriteLine(valueA);
char japaneseA = Convert.ToChar(valueA);
Console.WriteLine(japaneseA);

Works with ASCII char or Unicode char