How Does the `yield` Keyword Work in C# to Create Iterators and Improve Performance?

In c#

Keywords: iterator and performance optimization yield The keyword plays a vital role in C#. It simplifies the implementation of the enumers and the creation of iterators, and significantly improves the readability and performance of the code. Let us understand its functions in depth.

Gradually return the result (yield)

The keyword allowed method is suspended and the results are gradually returned. When the call function iterates an object of the Yielding Results interface, the method of keywords is repeatedly called until the sequence is over. This mechanism is called "yielding".

For example, consider the following code fragment: yield IEnumerable yield Methods return to objects from

according to the conditions. When the recipe iteration result, this method will return each matching one by one.

Implement the iterator (

<code class="language-csharp">IEnumerable<object> FilteredList()
{
    foreach (object item in FullList)
    {
        if (IsItemInPartialList(item))
            yield return item;
    }
}</code>

)

FilteredList() FullList The keywords simplify the creation of the customizer. In the early version of C#, the

object must be manually implemented by the object.

Provides a more concise and more statement method: Implementing Iterators This code returns an integer sequence without explicit iterative logic.

Actual application (yield) IEnumerator yield

In practical applications,

<code class="language-csharp">public IEnumerable<int> Integers()
{
    yield return 1;
    yield return 2;
    yield return 4;
    yield return 8;
    yield return 16;
    yield return 16777216;
}</code>

is often used in inertial value of value, such as retrieved data from a database. Consider the following example:

This method constructs a enumerator, obtains a record from the database table, and creates an object with the mapping function

to create the type T. By using , this method avoid loading the entire result set to the memory, so as to improve performance when processing large data sets.

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