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What is the purpose of Deconstruct method in KeyValuePair<> struct?

I was looking at System.Collections.Generic.KeyValuePair<TKey, TValue> struct in System.Runtime, Version=4.2.1.0 and this method took my attention.

System.Collections.Generic.KeyValuePair<TKey, TValue>

System.Runtime, Version=4.2.1.0

Here's the signature:

public void Deconstruct(out TKey key, out TValue value);


Does it contain any logic besides simply forwarding Key and Value properties? Why would anyone ever prefer it over property getters?

Key

Value

var (key, value) = SomeMethodReturningAKeyValuePair()

1 Answer
1

Deconstruction is a feature that was introduced mainly for value tuples in C# 7, letting you "unpackage all the items in a tuple in a single operation". The syntax has been generalized to allow it to be used for other types too. By defining the Deconstruct method, you can then use concise deconstruction syntax to assign the internal values to individual variables:

Deconstruct

var kvp = new KeyValuePair<int, string>(10, "John");
var (id, name) = kvp;


You can even apply deconstruction to your own user-defined types by defining such a Deconstruct method with out parameters and a void return type, like in your example. See Deconstructing user-defined types.

Deconstruct

out

void

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