Per Document Data (.NET)

Global data can be temporally stored in memory at the document level.

When the AutoCAD program loads a managed application, it queries the application's assembly for one or more PerDocumentClass custom attributes. If instances of this attribute are found, an instance of each attribute's associated type is created for each document open in the AutoCAD drawing environment. New instances of the types are then created for any documents that are opened thereafter.

The type associated with a PerDocumentClass attribute must provide either a Public constructor that takes a document argument or a Public Static Create method that takes a document argument and returns an instance of the type. If the Create method exists, it will be used, otherwise the constructor will be used. The document that the type instance is being created for will be passed as the document argument so that the type instance knows with which document it is associated.

The following procedure describes how to use the PerDocumentClass attribute.

1. In the assembly context, declare a PerDocumentClass attribute for each class that you want to be instantiated for each document.
2. Pass the type of the class to the PerDocumentClass attribute.

Note: This attribute must be declared in the assembly context.

VB.NET

...
Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.Runtime

<Assembly: PerDocumentClass(GetType(PerDocData))> 

' Defines a global class for constant values
Public NotInheritable Class CSPerDocConsts
    Private Sub New()
    End Sub

    Public Const dbLocVarName As String = "dbLoc"
End Class

' Defines the main class
Public Class PerDocCommands
    ' Creates a command that returns the current value of the per document data
    <CommandMethod("DatabaseLocation")> _
    Public Sub DatabaseLocation()
        Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument
        Dim pDData As PerDocData = DirectCast(acDoc.UserData(CSPerDocConsts.dbLocVarName), PerDocData)
        If pDData Is Nothing Then
            acDoc.Editor.WriteMessage(vbLf & "No user data assigned.")
        Else
            acDoc.Editor.WriteMessage(vbLf & pDData.DbLocation)
        End If
    End Sub
End Class

' Defines the class that wuill be used to initialize the per document data
Public Class PerDocData
    ' Define the internal/member variables of the class
    Private _stDbLoc As String

    ' Expose a public property that returns the value of the internal variable
    Public ReadOnly Property DbLocation() As String
        Get
            Return _stDbLoc
        End Get
    End Property

    ' Public constructor that requires a Document object
    ' Created by AutoCAD when the application is loaded
    Public Sub New(acDoc As Document)
        _stDbLoc = ""
        acDoc.UserData.Add(CSPerDocConsts.dbLocVarName, Me)
    End Sub

    ' Create method: Required constructor for the class
    Public Shared Function Create(acDoc As Document) As PerDocData
        Dim pDData As New PerDocData(acDoc)
        pDData._stDbLoc = "C:\ABCApp\Data\" & acDoc.Name.Remove(acDoc.Name.Length - 4) & ".db"

        Return pDData
    End Function
End Class

C#

...
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.Runtime;

[assembly: PerDocumentClass(typeof(CSPerDoc.PerDocData))]

namespace CSPerDoc
{
    // Defines a global class for constant values
    public static class CSPerDocConsts
    {
        public const string dbLocVarName = "dbLoc";
    }

    // Defines the main class
    public class PerDocCommands
    {
        // Creates a command that returns the current value of the per document data
        [CommandMethod("DatabaseLocation")]
        public void DatabaseLocation()
        {
            Document acDoc = Application.DocumentManager.MdiActiveDocument;
            PerDocData pDData = (PerDocData) acDoc.UserData[CSPerDocConsts.dbLocVarName];
            if (pDData == null) {
                acDoc.Editor.WriteMessage("\nNo user data assigned.");
            } else {
                acDoc.Editor.WriteMessage("\n" + pDData.DbLocation);
            }
        }
    }

    // Defines the class that wuill be used to initialize the per document data
    public class PerDocData
    {
        // Define the internal/member variables of the class
        private string _stDbLoc;

        // Expose a public property that returns the value of the internal variable
        public string DbLocation
        {
            get { return _stDbLoc; }
        }

        // Public constructor that requires a Document object
        // Created by AutoCAD when the application is loaded
        public PerDocData(Document acDoc)
        {
            _stDbLoc = @"";
            acDoc.UserData.Add(CSPerDocConsts.dbLocVarName, this);
        }

        // Create method: Required constructor for the class
        public static PerDocData Create(Document acDoc)
        {
            PerDocData pDData = new PerDocData(acDoc);
            pDData._stDbLoc = @"C:\\ABCApp\\ProjectData\\" + acDoc.Name.Remove(acDoc.Name.Length - 4) + ".db";

            return pDData;
        }
    }
}