Thank you for the explanation Stéphane.
When I use MapWinGIS.ShapefileClass() instead of MapWinGIS.Shapefile():
import clr
clr.AddReferenceToFileAndPath("C:/mapwindow_dlls/Interop.MapWinGIS.dll")
import MapWinGIS
sf = MapWinGIS.ShapefileClass()
shpfilename = "C:/example.shp"
sf.Open(shpfilename, None) # raises Error
It raises an error:
Could not convert argument 0 for call to Open.
I googled a couple of times, and found one place where the same issue has
emerged: here on stackoverflow.
Stackoverflow issue is actually not related with ironpython, but with
ironruby. The author states that the solution is to supply the CLR string as an
argument to "Open" function, instead of regular ruby string. I tried that
replicating that in ironpython:
shpfilename = clr.Reference[System.String]("c:/example.shp")
But again the upper error message, did not go away.
Further googling found that this kind of issues may happen when trying to call
methods in .NET from "Interop COM objects". But only if that method has "ref
parameters". Which Open method does not. Here is the signature of the Open
method:
Help on method-descriptor Open Open(...)
Open(self: ShapefileClass, ShapefileName: str, cBack: Callback) -> bool
// MapWinGIS.ShapefileClass
[DispId(11)]
[MethodImpl(MethodImplOptions.InternalCall)]
public virtual extern bool Open([MarshalAs(UnmanagedType.BStr)] [In] string
ShapefileName, [MarshalAs(UnmanagedType.Interface)] [In] ICallback cBack =
null);
I would be very grateful for any kind of advice Stéphane.
Kind regards,
Djordje Spasic
From: Stéphane Lozier <[email protected]>
To: Djordje Spasic <[email protected]>
Cc: "[email protected]" <[email protected]>
Sent: Friday, January 29, 2016 5:24 PM
Subject: Re: [Ironpython-users] Cannot create instances of that class because
it is abstract
Shapefile is an interface with a CoClassAttribute to ShapefileClass (which
means when you do new Shapefile() in C# it creates an instance of
ShapefileClass). I have no idea what the correct behaviour for IronPython
should be, but in this case MapWinGIS.Shapefile gives you the interface.
You could try MapWinGIS.ShapefileClass() instead of MapWinGIS.Shapefile().
On Mon, Jan 25, 2016 at 11:03 AM, Djordje Spasic via Ironpython-users
<[email protected]> wrote:
Hello,
I am trying to call a specific method ("Open") from the .NET assembly.The .NET
assembly along with all other .dlls and necessary files, can be downloaded from
here. It's free an open source project: MapWindow.
In their examples page, by loading the Interop.MapWinGIS.dll file, they call
the MapWinGIS.Shapefile.Open() method like so:
using MapWinGIS;
string shpfilename = "C:/example.shp";
Shapefile sf = new Shapefile();
if (sf.Open(shpfilename, null))
{
}
However, when I try the same thing in ironpython:
import clr
import os
shpfilename = "C:/example.shp"
dllsfilename = "C:/mapwindow_dlls"
clr.AddReferenceToFileAndPath(os.path.join(dllsfilename,
"Interop.MapWinGIS.dll"))
print "Interop.MapWinGIS.dll loaded: ", "Interop.MapWinGIS" in
[assembly.GetName().Name for assembly in clr.References] # prints: True
import MapWinGIS
sf = MapWinGIS.Shapefile() # raises Error
sf.Open(shpfilename, None)
I am getting an error message:
"Message: Cannot create instances of Shapefile because it is abstract"
Why is this happening?
I contacted the author of the project, but couldn't solve the issue.
Any kind of advice would be helpful.
Kind regards,
Djordje Spasic
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