Edit: By request, I added a check to make sure the value entered was within the ASCII range of 0 to 127. Whether you want to limit this is up to you. In C# (and I believe .NET in general), chars are represented using UTF-16, so any valid UTF-16 character value could be cast into it. However, it is possible a system does not know what every Unicode character should look like so it may show up incorrectly.

// Read a line of input
string input = Console.ReadLine();

int value;
// Try to parse the input into an Int32
if (Int32.TryParse(input, out value)) {
    // Parse was successful
    if (value >= 0 and value < 128) {
        //value entered was within the valid ASCII range
        //cast value to a char and print it
        char c = (char)value;
        Console.WriteLine(c);
    }
}