According to your post in the .NET forum, it seems you have already know how to use Autodesk.Gis.Map.ImportExport.Importer xlass to import *.MIF file. You only need to configure the Importer a bit more details: setting up each InputLayer.
By default, if you do nothing about the InputLayer, AutoCAD Map will use the map layer name as AutoCAD layer name and use the Coordinate System of the map, and ignore the attribute data (only import geometries). You can setting up the InputLayer as you needed: using different Coordinate system (Map will automatically does the CS conversion); using desired AutoCAD layer name; and importing attribute data as Object Data. In your case, you need to call InputLayer.SetDataMapping(). The code would be like:
foreach (InputLayer layer in _importer)
{
// If needed, change the CS
layer.TargetCoordinateSystem = layer.OriginalCoordinateSys; // or whatever CS
// If needed, use desired CAD layer name, other than the default (Map layer name)
layer.SetLayerName(LayerNameType.LayerNameDirect, "MyDesiredLayerName");
if ([I need import OD])
{
layer.SetDataMapping(ImportDataMapping.NewObjectDataOnly, "[OD Table Name]")
}
}
Obviously, the the import source has multiple layers, you want to make sure the layer name/OD table name do not duplicate. Usually, you would simply use the map layer name for both CAD layer name and OD Table name.
Hope this helps.