Introducing C# 10: Extended property patterns
source link: https://anthonygiretti.com/2021/07/27/introducing-c-10extended-property-patterns/
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Introducing C# 10: Extended property patterns
Introduction
C# 8 has introduced a new pattern: Property pattern. This pattern enables you to match on properties of the object examined, if you missed that feature, here is the Microsoft documentation here: Property pattern. C# 10 improves that pattern by simplifying access to nested properties. In the article I’ll show what it is.
Example
The following code sample shows a C# 8 tax calculator, which involves an object named CalculateTax and its nested property named ProvinceOrStateTaxProperty which is itself an object:
namespace DemoCsharp9 { public class ProvinceOrStateTaxProperty { public string ProvinceOrState { get; set; } }
public class CalculateTax { public string CountryName { get; set; } public ProvinceOrStateTaxProperty ProvinceTaxProperty { get; set; } }
public class Computing { private static decimal ComputePrice(CalculateTax calculate, decimal price) =>
calculate switch {
{ ProvinceTaxProperty: { ProvinceOrState: "Québec" } } => 1.14975M * price,
{ ProvinceTaxProperty: { ProvinceOrState: "Alberta" } } => 1.05M * price,
{ ProvinceTaxProperty: { ProvinceOrState: "Ontario" } } => 1.13M * price,
_ => 0
}; } }
The syntax to access the nested property is a bit verbose:
{ ProvinceTaxProperty: { ProvinceOrState: "Value" } }
C# 10 fixes that and allows to access directly the nested property by a dot:
namespace DemoCsharp10 { public class ProvinceOrStateTax { public string ProvinceOrState { get; set; } }
public class CountryTax { public string CountryName { get; set; } public ProvinceOrStateTax ProvinceTaxProperty { get; set; } }
public class Computing { private static decimal ComputePrice(CountryTax calculate, decimal price) =>
calculate switch {
{ ProvinceTaxProperty.ProvinceOrState: "Québec" } => 1.14975M * price,
{ ProvinceTaxProperty.ProvinceOrState: "Alberta" } => 1.05M * price,
{ ProvinceTaxProperty.ProvinceOrState: "Ontario" } => 1.13M * price,
_ => 0
}; } }
Much more practical isn’t it ? 
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