TheSwamp

Code Red => .NET => ACAD with .NET8+ => Topic started by: kdub_nz on January 03, 2024, 06:11:46 PM

Title: Playing with: Simple Pattern matching in if statement
Post by: kdub_nz on January 03, 2024, 06:11:46 PM

Code - C#: [Select]

1. global using static System.Console;  // just to save noise writing Console. prefix
2.  
3. // Add and remove the "" to change object o between string and int.
4. object o = "3";
5. int j = 4;
6. if (o is int i)     // <= here be magic !
7. {
8.   WriteLine($"{i} x {j} = {i * j}");
9. }
10. else {WriteLine("o is not an int so it cannot multiply!"); }
11.  
12.  

Title: Re: Playing with: Simple Pattern matching in if statement
Post by: MickD on January 03, 2024, 07:33:37 PM

nice!  :-)

Title: Re: Playing with: Simple Pattern matching in if statement
Post by: kdub_nz on January 04, 2024, 01:04:02 AM

Yes Mick,

There has been a lot of nice stuff in the last 5 or 6 years that has been ignored because we were stuck with Framework 4.8

I just need to wrap my old brain around it all  :-D

Title: Re: Playing with: Simple Pattern matching in if statement
Post by: gile on January 04, 2024, 02:16:08 AM

Hi Kerry,

This was already available with C# 7 (and .NET Framework), see this topic (https://devblogs.microsoft.com/premier-developer/dissecting-the-pattern-matching-in-c-7/).

Title: Re: Playing with: Simple Pattern matching in if statement
Post by: gile on January 04, 2024, 03:42:37 AM

The same can been written with a switch statement (C# 7):

Code - C#: [Select]

1. switch (o)
2. {
3.     case int i:
4.         WriteLine($"{i} x {j} = {i * j}"); break;
5.     default:
6.         WriteLine("o is not an int so it cannot multiply!"); break;
7. }

C# 8 introduced "switch expressions":

Code - C#: [Select]

1. WriteLine(o switch
2. {
3.     int i => $"{i} x {j} = {i * j}",
4.     _ => "o is not an int so it cannot multiply!"
5. });

Title: Re: Playing with: Simple Pattern matching in if statement
Post by: kdub_nz on January 04, 2024, 04:21:37 AM

Thanks Gilles,
I missed that.

Title: Re: Playing with: Simple Pattern matching in if statement
Post by: gile on January 04, 2024, 05:31:24 PM

This way also works:

Code - C#: [Select]

1. WriteLine(
2.     o is int i ?
3.     $"{i} x {j} = {i * j}" :
4.     "o is not an int so it cannot multiply!");