How to Efficiently Break Out of Nested Loops in C#?

Efficiently exit C# nested loop

In programming, nested loops are often used to iterate over multiple collections or perform complex calculations. However, sometimes you may need to exit the inner and outer loops early, which can create performance and efficiency challenges.

Question:

If you have a nested for loop and want to exit both loops (inner and outer) efficiently, what is the fastest way? You may be hesitant to use Boolean values ​​or goto statements because of performance concerns or style preferences.

Solution:

While it is possible to use the goto statement, it is generally considered an outdated and inefficient approach. Consider the following alternatives:

1. Anonymous method (C#):

Anonymous methods allow you to define a function without specifying its name. This is useful in situations where you need to create custom loop behavior without the overhead of a full function declaration. In anonymous methods, you can use return statements to exit the inner and outer loops.

Example:

<code class="language-csharp">// 匿名方法
Action work = delegate
{
    for (int x = 0; x < 10; x++)
    {
        for (int y = 0; y < 10; y++)
        {
            if (/* 退出条件 */) return;
        }
    }
};
work();</code>

2. Local functions (C# 7 and above):

Local functions are a feature introduced in C# 7 that allow you to declare functions inside other methods. This provides similar effects to anonymous methods, but with a cleaner, more expressive syntax.

Example:

<code class="language-csharp">// 局部函数（在另一个方法内部声明）
void Work()
{
    for (int x = 0; x < 10; x++)
    {
        for (int y = 0; y < 10; y++)
        {
            if (/* 退出条件 */) return;
        }
    }
}</code>

These methods provide an efficient and elegant way to exit a nested loop in a single line of code. They can be used in situations where you need to terminate loop execution early and continue execution with the next section of code.

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