Switch char

In C# programs the switch can handle char cases. Because a char is a value, switch can use jump tables to test chars.

We can take a char value and get a full string version of it—using the switch statement on characters. Ranges of characters can be specified as multiple cases.

Required input, output

Suppose we want to expand single-char abbreviations into full strings. We can implement this with a C# switch statement.

a -> Area
b -> Box
c -> Cat
...

Example

There are several ways of looking up characters and getting equivalent values for them. Some options include if conditional statements, switch statements, and lookup tables.

using System;

class Program
{
    static void Main()
    {
        char input1 = char.Parse("s");
        string value1 = SwitchChar(input1);

        char input2 = char.Parse("c");
        string value2 = SwitchChar(input2);

        Console.WriteLine(value1);
        Console.WriteLine(value2);
        Console.WriteLine(SwitchChar('T'));
    }

    static string SwitchChar(char input)
    {
        switch (input)
        {
            case 'a':
                {
                    return "Area";
                }
            case 'b':
                {
                    return "Box";
                }
            case 'c':
                {
                    return "Cat";
                }
            case 'S':
            case 's':
                {
                    return "Spot";
                }
            case 'T':
            case 't':
                {
                    return "Test";
                }
            case 'U':
            case 'u':
                {
                    return "Under";
                }
            default:
                {
                    return "Deal";
                }
        }
    }
}
Spot
Cat
Test

Internals

Char switches result in the jump table instruction. Jump tables are a way to achieve much faster look up by using multiplication and addition instructions.

We can switch on the character type in the C# language. This is an efficient (and terse) way to find the values of individual characters.

Char, review

The switch statement on char is compiled into an efficient jump table, often providing faster lookup than if-statements. This pattern is worth using in C# programs.