Analysis of limitations of C# Switch statements

Although the switch statement of C# provides a convenient and easy-to-use program flow control method, it also has some specific limitations:

Integer switch expression

switch statement must be an integer value, that is, the basic data type. This limitation originates from the underlying Common Intermediate Language (CIL) switch directive, which requires a jump table mechanism.

adjacent Case statement

The adjacent case statement with continuous integer values ​​allows efficient CIL switch implementations by jumping tables. However, non-adjacent cases can reduce efficiency and may lead to if-else-if structures or binary tree searches.

Performance impact

The performance of switch statements in C# depends on the compiler optimization and specific scenarios. Use CILDASM to confirm:

• The switch of adjacent cases uses the CIL switch instruction, and the complexity is O(1).
• Switches with non-adjacent cases use binary tree search, complexity is O(log n).
• Sparse case switch may require initial lookup in the dictionary, introducing additional overhead.

String type exclusion

The switch statement cannot directly process string case expressions. They usually rely on dictionary-based lookups, which can affect performance.

Theoretical considerations

Some people might think that switch statements should support any type and case expression. However, the trade-off between efficiency and maintainability makes current design a reasonable compromise.