How to get indexes in C# foreach loop

1. Manually maintain index variables

Implementation method：
Declare the index variable outside the loop, incrementing manually for each iteration:

int index = 0; foreach (var item in collection) { ($"{index}: {item}"); index++; }

Features：

Simple and straightforward, no need to introduce additional dependencies 12.
Pay attention to thread safety and variable scope issues.

2. LINQ Select + Tuple Destruction

Implementation method：
Using LINQSelectMethods bind elements to indexes into tuples (C# 7.0+ supports tuple deconstruction syntax):

foreach (var (item, index) in ((value, i) => (value, i))) { ($"{index}: {item}"); }

Features：

The code is concise and avoids manual maintenance of index 13.
Need to be introducedNamespace.

3. Extension method encapsulate index

Implementation method：
Custom extension methodWithIndex, package the collection element and index back:

public static class EnumerableExtensions { public static IEnumerable&lt;(T item, int index)&gt; WithIndex&lt;T&gt;(this IEnumerable&lt;T&gt; source) { return ((item, index) =&gt; (item, index)); } } // Call foreach (var (item, index) in ()) { ($"{index}: {item}"); }

Features：

Enhanced code reusability, suitable for scenarios where indexes are frequently obtained 3.

4. Use for loop substitution

Implementation method：
If you need to operate the index directly, you can use it instead.forLoop:

for (int i = 0; i < ; i++) { var item = collection[i]; ($"{i}: {item}"); }

Features：

Direct access to indexes, suitable for collections that support indexers (such as arrays,List<T>）57。
Cannot be used for collections that do not support indexers (e.g.IEnumerable<T>）。

Method comparison and applicable scenarios

method	Applicable scenarios	advantage	limit
Manually maintain index variables	Simple scenarios, no complex dependencies required	No extra dependencies, flexible	Need to be managed manually, and errors are prone to
LINQ + Tuple Destruction	Projects that require concise syntax and support C# 7.0+	Compact code	Rely on LINQ, slightly lower performance
Extended Method	High reusability requirements	Reusable, clear code structure	Predefined extension classes
`for`Circular substitution	Sets that support indexers (arrays,`List<T>`wait)	Direct and efficient	Not applicable to`IEnumerable<T>`

Operation suggestions：

PriorityLINQ + Tuple DestructionorExtended Method, to keep code simplicity and maintainability 13.
Scenarios that are sensitive to performance, use them insteadforRun or manually maintain index 57.

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