if/else vs. switch-case in C#: When Should I Choose Which?

Comparison and selection of if/else and switch-case statements in C#

In C# programming, programmers often struggle with the difference in performance or functionality when choosing to use if/else statements or switch-case statements.

Analysis of advantages and disadvantages

Although both are used for conditional execution, they have their own characteristics:

• if/else: is more flexible and easier to implement when the number of conditions is small.
• switch-case: is optimized for multiple tests of a single variable or expression, resulting in better performance and more readable code.

Performance Considerations

In most cases, if/else and switch-case choices have little impact on the generated intermediate language (IL) or runtime performance. However, in optimization (Release) mode, switch-case statements are usually compiled into jump tables, achieving O(1) lookup time.

String-based switch statement

C# is unique in allowing switch-case evaluation of string constants. In this case, the compiler uses a different optimization strategy:

• A few cases: For efficiency, switch statements are usually compiled into a series of if/else statements.
• Lots of cases: The compiler generates hash tables to perform constant time lookups.

Suggestion

In general, if the number of conditions exceeds about five, it is recommended to use a switch-case statement because of its performance advantages. For situations where there are fewer conditions or where code readability is a priority, if/else statements may be more appropriate.

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