Why is this an issue?

When switch statements have large sets of case clauses, it is usually an attempt to map two sets of data. A Dictionary should be used instead to make the code more readable and maintainable.

Exceptions

This rule ignores switch statements over Enum arguments and empty, fall-through cases.

How to fix it

Store all the cases apart from the default one in a dictionary and try to get the matching value by calling the TryGetValue method.

Code examples

The example below are using the "Maximum number of case" property set to 4.

Noncompliant code example

public class TooManyCase
{
    public int mapValues(char ch)
    {
        switch(ch) {  // Noncompliant: 5 cases, "default" excluded, more than maximum = 4
            case 'a':
                return 1;
            case 'b':
            case 'c':
                return 2;
            case 'd':
                return 3;
            case 'e':
                return 4;
            case 'f':
            case 'g':
            case 'h':
                return 5;
            default:
                return 6;
        }
    }
}

Compliant solution

using System.Collections.Generic;

public class TooManyCase
{
    Dictionary<char, int> matching = new Dictionary<char, int>()
    {
        { 'a', 1 },
        { 'b', 2 },
        { 'c', 2 },
        { 'd', 3 },
        { 'e', 4 },
        { 'f', 5 },
        { 'g', 5 },
        { 'h', 5 }
    };

    public int mapValues(char ch)
    {
        int value;
        if (this.matching.TryGetValue(ch, out value)) {
            return value;
        } else {
            return 6;
        }
    }
}