Topic: Playing with: Simple Pattern matching in if statement

[kdub_nz]

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.  

[MickD]

nice! 

[kdub_nz]

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 

[gile]

Hi Kerry,

This was already available with C# 7 (and .NET Framework), see this topic.

[gile]

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. });

[kdub_nz]

Thanks Gilles,
I missed that.

[gile]

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!");