It is important to notice that in C# the char type is stored as Unicode UTF-16.
char c = (char)88;
or
char c = Convert.ToChar(88)
int asciiCode = (int)'A';
The literal must be ASCII equivalent. For example:
string str = "X?????????";
Console.WriteLine((int)str[0]);
Console.WriteLine((int)str[1]);
will print
X
3626
Extended ASCII ranges from 0 to 255.
Using the Symbol
char c = 'X';
Using the Unicode code
char c = '\u0058';
Using the Hexadecimal
char c = '\x0058';