`else if` vs. `switch`: Which Conditional Statement Offers Better Performance in C#?

C# performance comparison: else if vs. switch

In C# development, it is often confusing to choose between else if or switch statements to implement conditional judgment. This article dives into the performance differences between the two methods.

else if Implementation

The

else if statement checks each condition in turn until a match is found. For example:

<code class="language-csharp">int a = 5;

if (a == 1)
{
    // 代码
}
else if (a == 2)
{
    // 代码
}
else if (a == 3)
{
    // 代码
}
else if (a == 4)
{
    // 代码
}
else
    // 代码</code>

switch Implementation

The

switch statement compares the input value with multiple cases and executes the code block corresponding to the matching case. Same example:

<code class="language-csharp">int a = 5;

switch (a)
{
    case 1:
        // 代码
        break;

    case 2:
        // 代码
        break;

    case 3:
        // 代码
        break;

    case 4:
        // 代码
        break;

    default:
        // 代码
        break;
}</code>

Performance Considerations

When the number of cases is small, the performance difference between else if and switch is insignificant. However, as the number of cases increases, switch becomes more efficient.

This is because the switch statement is usually implemented using a lookup table or hash table when the number of cases exceeds five. This means that all cases have the same access time, regardless of order.

The

and else if statements check each condition sequentially. Therefore, the time to access the last condition will increase as the number of cases increases, which will lead to significant performance degradation for a large number of condition judgments.

Conclusion

For cases with a limited number of cases, the performance difference between else if and switch is negligible. However, when dealing with a large number of cases, for best performance, it is highly recommended to use the switch statement.

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