Question

I was following along with a book about WMI and Powershell, and it explains how to create a custom class in Powershell. It involves writing some C# code, and the add-type command. When I try to create multiple entries in the object with the += command, I get the following error:

Method invocation failed because [pawobject] doesn't contain a method named 'op_Addition'.
At line:23 char:14
+ $MyObjects += <<<<  $MyObject
    + CategoryInfo          : InvalidOperation: (op_Addition:String) [], RuntimeException
    + FullyQualifiedErrorId : MethodNotFound

The code I am using to create the class is this:

$source = @"
public class pawobject
{
    public string Description { get; set; }
    public string Name { get; set; }
    public int Number { get; set;}
}
"@

And to add it to PowerShell I use the following:

Add-Type $source -Language CSharpVersion3

The code to create a value is this:

$MyObject = New-Object -TypeName pawobject -Property @{
    Name = "MyObject5";
    Number = 200;
    Description = "Take3"
}

This creates a single $MyObject. From here is where my problems come. I tried to create the object with multiple entries like this:

$MyObjects += $MyObject

But I get the above error. I have tried

$MyObjects = $MyObjects + $MyObject

I looked around online, and tried adding the following code the the public class:

public static string Add(string a, string b) {
    return (a + b);
}

But that seems to only work with numbers. I am not familiar at all with C#, so I’m not even sure where to start looking to fix this error. I can see this being very useful, as I am always creating new objects in my environment. Being able to define our own types would be a tremendous advantage, especially being able to control what type of data can get put into each property. Thank you in advance, have a great day!

Edit: Let me explain what I want the results to do.

I want to be able to declare something like this this:

$MyObject = New-Object -TypeName pawobject -Property @{
    Name = "MyObject";
    Number = 100;
    Description = "Take1"
    }

When I take the output of $MyObject I end up with this:

Description   Name         Number
-----------   ----         ------
Take1         MyObject     100

I would like to then be able to declare this:

$MyObjects += $MyObjects

And end up with $MyObjects having this:

Description   Name         Number
-----------   ----         ------
Take1         MyObject     100
Take2         MyObject5    200

Basically adding (not sure of the technical term for adding two sets of objects) the $MyObject to $MyObjects

Answer 1

It’s interpretting it as adding two objects together
I think in c# you would need to implement the operate like this:

    public static pawobject operator +(pawobject A, pawobject B)
    {

        //I have no idea how you would add two of these together
    }

I’m not sure that this is actually what you want to do though. It seems like you want to create an array of objects.

I’ve tested this out and it does create an array of objects.

PS C:\Users\James> $source = @"
>> public class pawobject3
>> {
>>     public string Description { get; set; }
>>     public string Name { get; set; }
>>     public int Number { get; set;}
>>     public static pawobject3[] operator +(pawobject3 A, pawobject3 B)
>>     {
>>         pawobject3[] Result = new pawobject3[2];
>>         Result[0] = A;
>>         Result[1] = B;
>>         return Result;
>>     }
>>     public static pawobject3[] operator +(pawobject3[] A, pawobject3 B)
>>     {
>>         pawobject3[] Result = new pawobject3[A.Length + 1];
>>         for(int i = 0; i < A.Length; i++)
>>             Result[i] = A[i];
>>         Result[A.Length] = B;
>>         return Result;
>>     }
>> }
>> "@
>>
PS C:\Users\James> Add-Type $source -Language CSharpVersion3
PS C:\Users\James> $MyPaw1
PS C:\Users\James> $MyPaw1 = New-Object -TypeName pawobject3 -Property @{
>> Name = "Test1";
>> Number = 1;
>> Description = "D1";
>> }
>>
PS C:\Users\James> $MyPaw2 = New-Object -TypeName pawobject3 -Property @{
>> Name = "Test2";
>> Number = 2;
>> Description = "D2";
>> }
>>
PS C:\Users\James> $MyPaw3 = New-Object -TypeName pawobject3 -Property @{
>> Name = "Test3";
>> Number = 3;
>> Description = "D3";
>> }
>>
PS C:\Users\James> $MyPaws = $MyPaw1 + $MyPaw2
PS C:\Users\James> $MyPaws += $MyPaw3
PS C:\Users\James> $MyPaws

Description                             Name                                                                     Number
-----------                             ----                                                                     ------
D1                                      Test1                                                                         1
D2                                      Test2                                                                         2
D3                                      Test3                                                                         3

You need to make sure the operator knows what it’s adding together. There’s no declaration of variable type so to create the array I’m using the return type of adding 2 together.

Hope this helps