Quick Summary: Setting up development environment.

1. Context / Introduction

Overview: Revit Plugin Types

External Commands - Commands invoked from Add-in Tab and implements - IExternalCommand interface
External Applications - programmatically add or modify the UI (for instance, create custom ribbon tabs, panels, and buttons) and implements the IExternalApplication interface.
Transaction - In Revit, any operation that modifies a document must be executed within a transaction. A transaction is a set of actions that can be committed or rolled back as one unit, ensuring consistency in the document.
Transaction Modes: - When you decorate an external command class with the [Transaction] attribute, you specify the intended transaction mode. The available modes include:
- ReadOnly: Indicates that the command will not make any changes to the document. This is useful for commands that only read or display information.
- Manual: Requires you to manually start, commit, or roll back a transaction within your code if you intend to make changes.
- ReadWrite (not used in the examples): Automatically starts and commits a transaction if you’re making changes to the document.

2. Example: External Applications

Folder Organization

A typical folder structure might look like this: MyRevitPlugins/

├── MyRevitPlugins.sln

├── addins/

└── MyCustomRibbonApp.addin

└── MyRevitPlugins/

├── App.cs

├── CommandOne.cs

├── CommandTwo.cs

├── CommandThree.cs

└── MyRevitPlugins.csproj

MyRevitPlugins.sln: The solution file.
MyRevitPlugins.csproj: The project file for the assembly containing both the external application and the commands.
addins/MyCustomRibbonApp.addin: The Revit manifest file that tells Revit to load your external application when it starts.
App.cs: Contains your ribbon creator class (the external application).
CommandOne.cs, CommandTwo.cs, CommandThree.cs: Each of these defines a separate command.

Code snippet:

A. External Application – App.cs This class creates a custom ribbon tab and adds three buttons, each wired to an external command.

C#

using Autodesk.Revit.UI;
using System;
using System.Reflection;

namespace MyRevitPlugins
{
    public class App : IExternalApplication
    {
        public Result OnStartup(UIControlledApplication application)
        {
            string tabName = "My Custom Tab";

// Create a custom ribbon tab (ignore error if already exists)
            try
            {
                application.CreateRibbonTab(tabName);
            }
            catch (Exception)
            {
// If the tab already exists, you can ignore or log the exception.
            }

// Create a panel on the custom tab
            RibbonPanel panel = application.CreateRibbonPanel(tabName, "My Commands");

// Get the path to this assembly
			string assemblyPath = Assembly.GetExecutingAssembly().Location;

// Add Command One button
            PushButtonData btnData1 = new PushButtonData(
                "CommandOne", 
                "Command One", 
                assemblyPath, 
                "MyRevitPlugins.CommandOne");
            btnData1.ToolTip = "Executes Command One.";
            panel.AddItem(btnData1);

// Add Command Two button
            PushButtonData btnData2 = new PushButtonData(
                "CommandTwo", 
                "Command Two", 
                assemblyPath, 
                "MyRevitPlugins.CommandTwo");
            btnData2.ToolTip = "Executes Command Two.";
            panel.AddItem(btnData2);

// Add Command Three button
            PushButtonData btnData3 = new PushButtonData(
                "CommandThree", 
                "Command Three", 
                assemblyPath, 
                "MyRevitPlugins.CommandThree");
            btnData3.ToolTip = "Executes Command Three.";
            panel.AddItem(btnData3);

            return Result.Succeeded;
        }

        public Result OnShutdown(UIControlledApplication application)
        {
// Clean-up can be performed here.
            return Result.Succeeded;
        }
    }
}

External Command One – CommandOne.cs

This command simply shows a message dialog when executed.

using Autodesk.Revit.UI;
using Autodesk.Revit.DB;
using Autodesk.Revit.Attributes;

namespace MyRevitPlugins
{
    [Transaction(TransactionMode.ReadOnly)]
    public class CommandOne : IExternalCommand
    {
        public Result Execute(ExternalCommandData commandData, ref string message, ElementSet elements)
        {
            TaskDialog.Show("Command One", "Command One executed successfully.");
            return Result.Succeeded;
        }
    }
}

External Command Two – CommandTwo.cs

A similar command with its own message.

using Autodesk.Revit.UI;
using Autodesk.Revit.DB;
using Autodesk.Revit.Attributes;

namespace MyRevitPlugins
{
    [Transaction(TransactionMode.ReadOnly)]
    public class CommandTwo : IExternalCommand
    {
        public Result Execute(ExternalCommandData commandData, ref string message, ElementSet elements)
        {
            TaskDialog.Show("Command Two", "Command Two executed successfully.");
            return Result.Succeeded;
        }
    }
}

External Command Three – CommandThree.cs

And the third command:

using Autodesk.Revit.UI;
using Autodesk.Revit.DB;
using Autodesk.Revit.Attributes;

namespace MyRevitPlugins
{
    [Transaction(TransactionMode.ReadOnly)]
    public class CommandThree : IExternalCommand
    {
        public Result Execute(ExternalCommandData commandData, ref string message, ElementSet elements)
        {
            TaskDialog.Show("Command Three", "Command Three executed successfully.");
            return Result.Succeeded;
        }
    }
}

Add‑in Manifest File – MyCustomRibbonApp.addin

This XML file registers your external application with Revit. Place it in the “addins” folder (or copy it to the proper Revit add‑ins folder during build/deployment).

<?xml version="1.0" encoding="utf-8" standalone="no"?>
<RevitAddIns>
	  <AddIn Type="Application">
		    <Name>My Custom Ribbon App</Name>
		    <Assembly>MyRevitPlugins.dll</Assembly>
		    <FullClassName>MyRevitPlugins.App</FullClassName>
		    <AddInId>INSERT-YOUR-GUID-HERE</AddInId>
		    <VendorId>YourVendorID</VendorId>
		    <VendorDescription>Your Vendor Description</VendorDescription>
		    <VendorEmail>youremail@example.com</VendorEmail>
	  </AddIn>
</RevitAddIns>