To automate Inventor, you first need to get a reference to the Application object.
Scenario 1: Connect to a running instance
using Inventor; using System.Runtime.InteropServices;// ...
Application inventorApp = null;
try // Attempt to get the active Inventor application inventorApp = (Application)Marshal.GetActiveObject("Inventor.Application"); catch (COMException) // Inventor is not running Console.WriteLine("Inventor is not currently running.");
Scenario 2: Create a new instance
Type inventorType = Type.GetTypeFromProgID("Inventor.Application");
inventorApp = (Application)Activator.CreateInstance(inventorType);
inventorApp.Visible = true; // Make the window visible
You might need to generate 3D models or drawings without user interaction. For example, a configuration tool that creates custom parts based on database values. Your application launches Inventor (or attaches to a running instance) via the interop assembly.
Causes:
This legacy error appears when you reference an older interop DLL built against .NET 2.0 while your project targets .NET 4.x or newer.
Solution:
Add the following to your app.config file:
<startup useLegacyV2RuntimeActivationPolicy="true">
<supportedRuntime version="v4.0"/>
</startup>
Always set Copy Local = False for autodesk.inventor.interop.dll.
Why? Because Inventor already has the correct version in its own installation directory. Your add-in should always use the interop DLL from the Inventor version it is running against. If you copy it locally, your add-in might load a mismatched version, leading to System.InvalidCastException or MissingMethodException at runtime.
Correct reference settings in Visual Studio:
If you’ve ever opened the Object Browser in Visual Studio while working with Autodesk Inventor’s API, you’ve likely seen autodesk.inventor.interop.dll. It looks like just another reference, but misunderstanding it can lead to broken add-ins, version conflicts, and deployment headaches.
In this post, I’ll explain what this DLL actually is, when you need it, and how to use it correctly in your Inventor plug-ins.
Understanding Autodesk.Inventor.Interop.dll: The Key to Inventor API Development
The Autodesk.Inventor.Interop.dll is the primary bridge between the .NET framework and the internal Component Object Model (COM) of Autodesk Inventor. It is an essential library for any developer looking to automate design tasks, build custom add-ins, or create external applications that interact with Inventor data. What is the Autodesk.Inventor.Interop.dll?
This file is a Primary Interop Assembly (PIA). Because Autodesk Inventor is built on a COM-based architecture, modern programming languages like C# or VB.NET cannot communicate with it directly. The interop DLL acts as a "translator," exposing Inventor's functions, classes, and properties as manageable .NET objects. Core Functions and Use Cases
Developers use this library to access the Inventor API, enabling a wide range of automation possibilities:
Automation of Repetitive Tasks: Writing scripts to automatically generate parts, update parameters, or export drawings. autodesk.inventor.interop.dll
Custom Add-ins: Creating specialized ribbons and toolsets within the Inventor interface.
External Integration: Connecting Inventor with external ERP or PLM systems to sync bill of materials (BOM) data.
Geometric Manipulation: Using code to combine solid bodies or modify complex assemblies. How to Reference the DLL in Your Project
To start coding, you must first add a reference to this DLL in your development environment (typically Microsoft Visual Studio).
Locate the File: It is usually found in the Inventor installation directory (e.g., C:\Program Files\Autodesk\Inventor ).
Add Reference: In Visual Studio, right-click on your project's References and browse for Autodesk.Inventor.Interop.dll.
Set Properties: It is a best practice to set "Embed Interop Types" to True in the property window. This allows your application to run on different versions of Inventor without needing the exact DLL version on the user's machine.
Import Namespace: Add the following directive to the top of your code file: C#: using Inventor; VB.NET: Imports Inventor The Inventor Object Model
Once referenced, the DLL provides access to the hierarchical object model. At the top of this hierarchy is the Inventor.Application object, which represents the entire software session. From there, you can drill down into specific documents: PartDocument (.ipt): For individual component modeling.
AssemblyDocument (.iam): For managing relationships between components.
DrawingDocument (.idw/.dwg): For creating 2D production drawings. Common Challenges
Version Compatibility: While "Embed Interop Types" helps, major API changes between Inventor versions can occasionally break code. Always test your scripts against the specific Inventor release version you are targeting.
Performance: Extensive API calls can be slow. It is often faster to use iLogic for simple rule-based automation and the full API for complex, large-scale applications.
By mastering the Autodesk.Inventor.Interop.dll, developers can transform Inventor from a standard modeling tool into a highly customized engine tailored to specific engineering workflows. AI responses may include mistakes. Learn more
Lesson 3: A First Look at Code for my First Inventor Plug-In
The Autodesk.Inventor.Interop.dll is the primary Primary Interop Assembly (PIA) that allows .NET-based applications (like C# or VB.NET) to communicate with the Autodesk Inventor COM-based API. It acts as a bridge, translating managed .NET calls into the unmanaged COM commands that the Inventor software understands. Core Technical Concepts
COM Wrapper: Since Inventor's internal architecture is built on COM, this DLL "wraps" those objects into a format .NET developers can use.
File Location: Typically found in the Inventor installation directory under C:\Program Files\Autodesk\Inventor [Version]\Bin\Public Assemblies\.
Versioning: Each version of Inventor has its own specific interop version (e.g., Inventor 2026 uses version 30.0). Mismatches can cause "Could not load file or assembly" errors. Implementation and Deployment To automate Inventor, you first need to get
To use the interop library in a custom project (like a Visual Studio add-in):
Reference: Add a direct reference to the DLL from the Public Assemblies folder. Configuration:
Embed Interop Types: Usually set to False to avoid issues with event handling and specific COM types.
Copy Local: Set to True to ensure the specific version of the DLL is bundled with your compiled application.
Apprentice Server: For lightweight operations (like reading iProperties without launching the full Inventor GUI), developers use the Apprentice component also found within this interop. Known Challenges Vault 2026 Client outdated dlls - Forums, Autodesk
The file Autodesk.Inventor.Interop.dll is a primary assembly required for developers to interface with the Autodesk Inventor API using .NET languages like C# or VB.NET. It acts as a bridge (COM interop) between managed .NET code and Inventor's underlying COM-based object model. Key Locations
The DLL is typically located in the following directories on a machine with Inventor installed:
Standard Path: C:\Program Files\Autodesk\Inventor 20xx\Bin\Public Assemblies\Autodesk.Inventor.Interop.dll.
Global Assembly Cache (GAC): C:\Windows\Microsoft.NET\assembly\GAC_MSIL\Autodesk.Inventor.Interop\. Critical Usage Settings
When referencing this DLL in a Visual Studio project, the following property settings are essential for stability:
Embed Interop Types: Usually set to False. While setting it to True can simplify deployment by embedding the necessary COM types into your own assembly, it can cause issues with specific functions or events in some versions of Inventor.
Copy Local: Often set to True for standalone applications to ensure the DLL is present in the output folder, though it is not strictly required if Inventor is installed on the target machine because it is already in the GAC.
Specific Version: Set to False if you want your application to attempt to run on different versions of Inventor (e.g., using a 2018 reference to run on Inventor 2023). Common Issues Different version of Autodesk.Inventor.Interop.dll
Autodesk.Inventor.Interop.dll is the primary primary library required to programmatically control Autodesk Inventor using .NET languages like C# or Visual Basic. It acts as a bridge (COM Interop) between your managed code and Inventor's underlying COM-based API. www.hjalte.nl 1. Locating the DLL You will typically find the library in the folder of your Inventor installation: www.hjalte.nl
C:\Program Files\Autodesk\Inventor [Version]\Bin\Public Assemblies\Autodesk.Inventor.Interop.dll Alternative Path: Some versions may also store it directly in ...\Bin\Autodesk.Inventor.Interop.dll www.hjalte.nl 2. Setting Up Your Project
To use the DLL in Visual Studio, follow these critical configuration steps: Add Reference: Right-click your project, select Add Reference , and browse to the path mentioned above. Embed Interop Types: Set this property to . Keeping it at
(the default) can cause unexpected behavior, especially when working with legacy code or specific Inventor objects. Copy Local: Usually set to
if you are developing an Add-In that will run within Inventor's memory space). www.hjalte.nl 3. Basic Code Implementation The library exposes the Inventor.Application object, which is the root of the entire object model. Common C# Initialization: // Use the interop namespace // Attempt to get a running instance of Inventor
Application _invApp = (Application)System.Runtime.InteropServices.Marshal.GetActiveObject( "Inventor.Application" Use code with caution. Copied to clipboard 4. Core Object Model Hierarchy Understanding the Inventor Object Model is essential for effective use of the DLL: Application: The top-level object. Documents: Provides access to all open files ( PartDocument AssemblyDocument DrawingDocument ComponentDefinition: Scenario 2: Create a new instance Type inventorType
Found within Part and Assembly documents; this is where you modify geometry or parameters. Parameters: Allows you to read and write dimensions programmatically. 5. Troubleshooting & Tips Version Compatibility:
Ensure your project targets a .NET Framework version compatible with your Inventor version (e.g., Inventor 2025 typically requires .NET 8). Debugging:
If your program won't start, set the "Start Action" in your project properties to point directly to Inventor.exe iLogic Integration:
If you need to trigger iLogic rules via your code, you will also need to reference Autodesk.iLogic.Interfaces.dll www.hjalte.nl creating an Add-In Creating an Inventor Addin - Jelte de Jong
To prepare content for or use the Autodesk.Inventor.Interop.dll
, you must add it as a project reference in your development environment (typically Visual Studio). This Primary Interop Assembly (PIA) acts as the bridge between your .NET code (C# or VB.NET) and the COM-based Autodesk Inventor API. 1. Locate the DLL
The DLL is installed automatically with Autodesk Inventor. You can find it at the following default paths: Primary Location:
C:\Program Files\Autodesk\Inventor [Version]\Bin\Public Assemblies\Autodesk.Inventor.Interop.dll GAC Backup:
C:\Windows\Microsoft.NET\assembly\GAC_MSIL\Autodesk.Inventor.Interop\ Autodesk Community, Autodesk Forums, Autodesk Forum 2. Add the Reference in Visual Studio
To use the Inventor API in your project, follow these steps: Right-click your project in the Solution Explorer and select
To develop a 3D solid text using the Autodesk.Inventor.Interop.dll, you must first reference the library in your project and then use the EmbossFeatures or ExtrudeFeatures objects to turn a text sketch into a solid body. 1. Setup the Environment
You must add a reference to the Autodesk.Inventor.Interop.dll in your Visual Studio project to access the Inventor API .
Location: Typically found in C:\Program Files\Autodesk\Inventor 20xx\Bin\Public Assemblies.
Properties: Set "Embed Interop Types" to False and "Copy Local" to True to ensure proper runtime referencing from the Global Assembly Cache (GAC). 2. Implementation Steps
Developing solid text involves a three-step programmatic workflow: A. Create a Sketch and Add Text
Create a PlanarSketch on a part face or work plane, then add a TextBox containing your string.
' Example: Creating a text box on a sketch Dim oSketch As PlanarSketch = oCompDef.Sketches.Add(oWorkPlane) Dim oPoint As Point2d = oTransGeom.CreatePoint2d(0, 0) Dim oTextBox As TextBox = oSketch.TextBoxes.AddFormattedText("Your Text Here", oPoint) Use code with caution. Copied to clipboard B. Select the Profile
The text box acts as the profile for your 3D feature. Use the Profile property of the sketch to capture the text geometry. C. Apply the 3D Feature You have two primary options to create the "solid" effect:
Embossing: Use the EmbossFeatures Object to raise or recess text relative to a face. This is ideal for curved surfaces.
Extruding: Use ExtrudeFeatures to create a standard 3D solid from the text profile. This is better for simple, flat-surface 3D text. Different version of Autodesk.Inventor.Interop.dll