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.

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;
        }
    }
}