What’s New in C# 10: Simplify Nested Property Pattern Code
source link: http://dontcodetired.com/blog/post/Whats-New-in-C-10-Simplify-Nested-Property-Pattern-Code
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What’s New in C# 10: Simplify Nested Property Pattern Code
This is part of a series on the new features introduced with C# 10.
Pattern matching in C# was first introduced in C# 7 and has been added to in later versions.
C# 8 added property pattern matching to allow you to match on the values of properties and fields. Prior to C# 10, property pattern matching with simple (non-nested) types was fine but if the thing you were matching was in a nested property the syntax was slightly clumsy:
public record CurrencyExchangeRate(string SourceCurrencyCode,string DestinationCurrencyCode,decimal ExchangeRate);public record Trade(int CustomerId, CurrencyExchangeRate ExchangeRate);In the preceding code we have a Trade that has a nested CurrencyExchangeRate, in C# 9 if we wanted to match on this nested CurrencyExchangeRate such as the SourceCurrencyCode, we’d have to use the following syntax:
public static bool IsRelatedToAustralia(Trade trade) =>trade is { ExchangeRate: { SourceCurrencyCode: "AUD" } } or{ ExchangeRate: { DestinationCurrencyCode: "AUD" } };Notice the extra nested {} to access the nested currency codes.
From C# 10 you can access nested properties directly which makes the code a little more readable, for example:
static bool IsRelatedToAustralia(Trade trade) =>trade is { ExchangeRate.SourceCurrencyCode: "AUD" } or{ ExchangeRate.DestinationCurrencyCode: "AUD" };If you want to fill in the gaps in your C# knowledge be sure to check out my C# Tips and Traps training course from Pluralsight – get started with a free trial.
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