Return code point of characters in C#

The following code writes the codepoints of a string input to the console:

string input = "\uD834\uDD61";

for (var i = 0; i < input.Length; i += char.IsSurrogatePair(input, i) ? 2 : 1)
{
    var codepoint = char.ConvertToUtf32(input, i);

    Console.WriteLine("U+{0:X4}", codepoint);
}

Output:

U+1D161

Since strings in .NET are UTF-16 encoded, the char values that make up the string need to be converted to UTF-32 first.

Easy, since chars in C# is actually UTF16 code points:

char x = 'A';
Console.WriteLine("U+{0:x4}", (int)x);

To address the comments, A char in C# is a 16 bit number, and holds a UTF16 code point. Code points above 16 the bit space cannot be represented in a C# character. Characters in C# is not variable width. A string however can have 2 chars following each other, each being a code unit, forming a UTF16 code point. If you have a string input and characters above the 16 bit space, you can use char.IsSurrogatePair and Char.ConvertToUtf32, as suggested in another answer:

string input = ....
for(int i = 0 ; i < input.Length ; i += Char.IsSurrogatePair(input,i) ? 2 : 1)
{
    int x = Char.ConvertToUtf32(input, i);
    Console.WriteLine("U+{0:X4}", x);
}

C# cannot store unicode codepoints in a char, as char is only 2 bytes and unicode codepoints routinely exceed that length. The solution is to either represent a codepoint as a sequence of bytes (either as a byte array or "flattened" into a 32-bit primitive) or as a string. The accepted answer converts to UTF32, but that's not always ideal.

This is the code we use to split a string into its unicode codepoint components, but preserving the native UTF-16 encoding. The result is an enumerable that can be used to compare (sub)strings natively in C#/.NET:

    public class InvalidEncodingException : System.Exception
    { }

    public static IEnumerable<string> UnicodeCodepoints(this string s)
    {
        for (int i = 0; i < s.Length; ++i)
        {
            if (Char.IsSurrogate(s[i]))
            {
                if (s.Length < i + 2)
                {
                    throw new InvalidEncodingException();
                }
                yield return string.Format("{0}{1}", s[i], s[++i]);
            }
            else
            {
                yield return string.Format("{0}", s[i]);
            }
        }
    }
}