IEnumerable vs. List in C#: When Should I Use Which for Optimal Performance?

C#collection: comparison of the performance of IenumerabLE and List and the best practice

When processing the set in C#, select

or

is essential for performance and efficiency. Although both represent the element sequence, the implementation method is very different. IEnumerable List IenumerabLE: abstract interface

is an interface that defines the behavior of the element sequence. It provides the operation of traversal sequence elements, but does not need to load the entire sequence to memory. This allows high -efficiency to handle large data sets because data is delayed.

List: The specific collection class

IEnumerable

is the specific implementation of the set of sorting elements. It provides a complete representation of the sequence in memory and allows to quickly access specific elements through indexes. However, this advantage is accompanied by performance costs because loading the entire sequence to memory may be very consumed.

Use scene

Choose or List, please consider the following guidelines:

Using Situation:

Need to handle large datasets and delay processing.

IEnumerable Want to avoid the overhead of the sequence to the memory. List

Want to link Linq expression and delay the value.

• IEnumerable
  Using Situation:
  You need to frequently access elements through index.
  Databases are small and can be loaded into memory efficiently.
  Want to avoid repeatedly executed inquiries.
• List
  Performance optimization
  • In order to optimize performance, it is generally recommended to use
  instead of
  • unless there are specific index access needs. By delay loading and link Linq expression,
  can highly delay processing data.
Example

Consider the following linq query:

Use to allow delay to find value query. If is used to specifically result, it will mandate the entire sequence to the memory, which may affect performance. IEnumerable List More resources IEnumerable

MSDN document

<code class="language-csharp">IEnumerable<animal> sel = (from animal in Animals 
                    join race in Species
                    on animal.SpeciesKey equals race.SpeciesKey
                    select animal).Distinct();</code>

MSDN document

IEnumerable ToList()

Document

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