How to BinarySearch Generic List in PowerShell

Question

I would like to binarysort a generic list of pscustomobject, but I don't know how to write code for it.
Do anyone know how to write the code for binarysearching a pscustomobject list?

array of pscustomobject

$list1 =
[pscustomobject]@{Id = 5; Name = "Tom"},
[pscustomobject]@{Id = 1 ; Name = "Ben"},
[pscustomobject]@{Id = 8 ; Name = "Alice"},
[pscustomobject]@{Id = 4 ; Name = "Lucy"},
[pscustomobject]@{Id = 9 ; Name = "Sam"},
[pscustomobject]@{Id = 7 ; Name = "Bill"}

Generic List of pscustomobject

using namespace System.Collections.Generic;
$l1 = [List[PSCustomObject]]::new()
$list1 | % {$l1.add($_)}

Sort the list

$l1.Sort( { $args[0].name.compareto($args[1].name) })

The follwing code doesn't work...

PS> $l1.BinarySearch({$args.Name -eq "Ben"})

Error

MethodInvocationException: Exception calling "BinarySearch" with "1" argument(s): "Failed to compare two elements in the array."

Answer 1

Hi,

The Array.BinarySearch method doesn't accept the -eq expression. You have to uses the IComparer interface
https://learn.microsoft.com/en-us/dotnet/api/system.array.binarysearch?view=net-5.0#System_Array_BinarySearch_System_Array_System_Object_System_Collections_IComparer_

The code could be like this

Class ObjComparer : IComparer[System.Object] {  
    [System.Object]$x  
    [System.Object]$y  
    [int]Compare($x,$y) {  
        return [System.Collections.CaseInsensitiveComparer]::new().Compare($x.Name, $y)  
    }  
}  
$l1.BinarySearch("Ben", [ObjComparer]::new())  

Best Regards，
Ian Xue

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