.NET

[#1]

Add these lines to the top of the class

Imports Autodesk.AutoCAD.DatabaseServices
Imports Autodesk.AutoCAD.Colors

and add the reference to

acdbmgr.dll

acmgd.dll

and set copy local to false.

[#2]

What  namespaces have you imported? Is this a standalone EXE application? 

[#3]

the above code won't work for a stand alone exe.

[#4]

Hi

I have the following imports:

Imports System
Imports System.Runtime.InteropServices
Imports Autodesk.AutoCAD.Interop

And yes this is a standalone EXE Application

[#5]

Hi

I have the following imports:

Imports System
Imports System.Runtime.InteropServices
Imports Autodesk.AutoCAD.Interop

And yes this is a standalone EXE application

[#6 · Accepted solution]

Try something like this to set the layer colors:

    Private Sub WorkingWithAutoCAD()
        ' we can set the color of one layer or current by:
        acSetLayerColor(AcColor.acYellow)
        'or
        'set them all to green
        For Each oLayer As AcadLayer In ThisApplication.ActiveDocument.Layers
            acSetLayerColor(AcColor.acGreen, oLayer)
        Next
        ' or set the OB layer to red and see if it happened calling by name
        Dim Rval As Boolean = acSetLayerColorByName(AcColor.acRed, "OB")

    End Sub

    Private Function acSetLayerColor(ByVal oColor As AcColor, Optional ByVal oLayer As AcadLayer = Nothing) As Boolean
        Try
            If oLayer Is Nothing Then 'we will look at the current layer
                oLayer = ThisApplication.ActiveDocument.ActiveLayer
            End If
            oLayer.color = oColor
            Return True
        Catch ex As Exception
            Return False
        End Try
    End Function

    Private Function acSetLayerColorByName(ByVal oColor As AcColor, ByVal oLayerName As String) As Boolean
        Try
            Dim oLayer As AcadLayer = ThisApplication.ActiveDocument.Layers.Item(oLayerName)
            oLayer.color = oColor
            Return True
        Catch ex As Exception
            Return False
        End Try
    End Function

[#7]

Hi

Your suggestions worked after I added a reference to acdbmgd.dll and acdmgd.dll and imported these namespaces:

Imports Autodesk.AutoCAD.DatabaseServices
Imports Autodesk.AutoCAD.Colors

Thank you all for your help.

Best regards