iLogic Error The object reference was not set to an object instance

[mk92]

Hi,

I took the code from this help page:

Autodesk Help Page

And made this out of it (just an extraction):

Dim newInst2 As Autodesk.Factory.PublicAPI.Objects.v2.AssetInstance = New Autodesk.Factory.PublicAPI.Objects.v2.AssetInstance() With {
            .AssetID = "41c84844-7b28-4903-bebd-365ca3a6a53c",	
		.Position = New System.Windows.Media.Media3D.Matrix3D() With {
            .OffsetX = -200,
            .OffsetY = 0,
            .OffsetZ = 0
        }
    }
newInst2.Parameters("Length") = "400"

The code runs great until I want to change the Length. Then is says;

The object reference was not set to an object instance.

I thought "Dim newInst2 As ...." is doing exactly this. What is missing here?

Thank you.

[bradeneuropeArthur]

Does the parameter "Length" exist?

Otherwise create it first!

[mk92]

Yes the parameter Length definitely exists.

If I do it like this:

Dim Layout As Document = ThisApplication.ActiveDocument	
Dim insts = api.AddAssetInstances(Layout, New Autodesk.Factory.PublicAPI.Currency.v2.IAssetInstance() {newInst1, newInst2, newInst3 })

Dim Test = api.GetAssetInstances(Layout)
For Each item In Test
	item.Parameters("Length") = "400"
Next
api.UpdateAssetInstances(Layout, Test)

It works fine, but for each asset with the parameter Length.

But I only want to edit specific assets. And for the best workflow right after they are placed in my layout.