Cannot create ActiveX component.Error while using GetObject in autocad 2011 - vb.net

Question

I am using below code to use autocad object.
Dim acadapp As AcadApplication
acadapp = GetObject(, "AutoCAD.Application")
'''and using below code to create object -------------
acadapp = CreateObject("AutoCAD.Application")
Getting error "Cannot create ActiveX component".
I tried using 18,19 and various combination as below :
acadapp = GetObject(, "AutoCAD.Application.18")
But nothing work.
Please help.
#Locke : Thanks for reply.I tried your soltion as below :
Dim acadType As Type
Try
acadapp =
System.Runtime.InteropServices.Marshal.GetActiveObject("AutoCAD.Application.18.1")
''Above code din't worked so tried below code also
' acadapp = DirectCast(Marshal.GetActiveObject("AutoCAD.Application.18.1"),
'AcadApplication)
Catch ex As Exception
acadType = Type.GetTypeFromProgID("AutoCAD.Application")
acadapp = DirectCast(Activator.CreateInstance(acadType, True), AcadApplication)
End Try
Showing Exception :
Unable to cast COM object of type 'System.__ComObject' to interface type 'AutoCAD.AcadApplication'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{8E75D910-3D21-11D2-85C4-080009A0C626}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).

Answer 1

Here's what I typically use when dealing with AutoCAD interop. It checks for a running instance, and creates a new one if necessary:
private static AcadApplication GetAcadApp(string progId)
{
// Create the return application
AcadApplication returnApp = null;
try
{
// Try getting a running instance
returnApp = (AcadApplication)Marshal.GetActiveObject(progId);
}
catch (COMException)
{
try
{
// Try creating a new instance
Type acadType = Type.GetTypeFromProgID(progId);
returnApp = (AcadApplication)Activator.CreateInstance(acadType, true);
}
catch (COMException)
{
// Report failure
MessageBox.Show(string.Format("Cannot create object of type \"{0}\"", progId));
}
}
// Return the application
return returnApp;
}
An AcadApplication COM object can be set like this:
// Get/create an AutoCAD instance
var acadApp = getAcadApp("AutoCAD.Application.18");
Regardless of C# or VB.NET, using Marshal.GetActiveObject and Activator.CreateInstance are probably the better ways to approach this.

Answer 2

According to the exception, the problem is not the GetActiveObject() call, but that the returned object doesn't support the interface you're looking for. Most likely reason is that your code references a different version of AcadApplication than the one you're getting back from GetActiveObject(). Change your project to reference the COM library version for the returned AutoCAD instance, and it should work fine.