Developers and Programming - Chapter 1: Building a Simple Add-in Application

In this chapter, you'll learn how to build your first MicroStation add-in application from scratch. We'll walk through each step to create a simple "Hello World" application and then load and run it inside MicroStation.

Launch Visual Studio

Select Visual Studio 2022 (right click and Run as administrator).

Create new project

In Visual Studio 2022, select “Create a new project”.

In the “Create a new project” form,

On the left side of the form, select “Class Library”.

On the right side of the form, select “Class Library (.NET Framework)”.

Note: The Class Library may have multiple options, select the correct type “Class Library (.NET Framework)”, a C# class library (.dll) as shown below.

Click on the “Next” button.

In the “Configure your new project” form,

Enter Project Name as “csAddins”

Select a Location

Set Framework to “.NET Framework 4.8”

Click on the “Create” button.

On the left is the automatically generated C# code, and on the right is the Solution Explorer form.

Set Add-in DLL path

In the Solution Explorer,

Select “csAddins”

Right click and select “Properties”

On the “Build” page, under the “Output path”, click “Browse” button
and navigate/choose the following path.

C:\Program Files\Bentley\MicroStation 2026\MicroStation\Mdlapps\

Note: By default, MicroStation searches for Add-ins in the Mdlapps folder.

If your Add-in DLL is created in a different location, set the MS_ADDINPATH configuration variable

to include the folder containing the DLL before attempting to load it.

Add References

In the Solution Explorer, right-click References and select Add Reference.

Under Assemblies > Framework, find/select the following library and click Ok button to add.
We will require the following library for the MessageBox class that will be used in our code.

System.Windows.Forms

Under Browse, find/select the following libraries and click the Ok button to add.

…\MicroStation\ustation.dll

…\MicroStation\Bentley.GeometryNET.dll

…\MicroStation\Bentley.GeometryNET.Common.dll

…\MicroStation\Bentley.GeometryNET.Structs.dll

…\MicroStation\Bentley.DgnDisplayNet.dll

…\MicroStation\Bentley.DgnPlatformNET.dll

…\MicroStation\Assemblies\Bentley.Interop.MicroStationDGN.dll

…\MicroStation\Assemblies\Bentley.MicroStation.dll

…\MicroStation\Assemblies\Bentley.MicroStation.Interfaces.1.0.dll

…\MicroStation\Assemblies\Bentley.MicroStation.Ribbon.dll

…\MicroStation\Assemblies\Bentley.MicroStation.WPF.dll

…\MicroStation\Assemblies\ECFramework\Bentley.General.1.0.dll

…\MicroStation\Assemblies\ECFramework\Bentley.Platform.dll

…\MicroStation\Assemblies\ECFramework\Bentley.UI.dll

…\MicroStation\Assemblies\ECFramework\Bentley.Windowing.dll

…\MicroStation\Assemblies\ECFramework\Bentley.EC.Persistence3.dll

…\MicroStation\Assemblies\ECFramework\Bentley.ECObjects3.dll

…\MicroStation\Assemblies\ECFramework\Bentley.ECSystem3.dll

…\MicroStation\Assemblies\ECFramework\Bentley.ECObjects.Interop3.dll

Note: If you only want to load programs and display a “Hello World” dialog box in MicroStation,

you can simply refer to the ustation.dll. The Bentley.MstnPlatfomNet.AddIn object is

included in this ustation.dll file. However, for future program expansions, including all

the above DLLs mean you don’t have to worry about which DLLs to add.

.NET loads DLLs on demand, so referenced libraries are only loaded when code uses their objects.

Unused libraries, or code paths that are never executed, will not cause the corresponding DLLs

to be loaded.

The final reference list is shown in the figure below:

Rename “Class1.cs”

Right-click “Class1.cs” in the solution browser and select Rename from the pop-up menu,

then change “Class1.cs” to “MyAddin.cs”.

Please select Yes to confirm the rename.

Note: This step is not required, but it's best to do it.

Modify “MyAddins.cs” and add the following code.

using Bentley.MstnPlatformNET;
using System.Windows.Forms;

namespace csAddins
{
    internal sealed class MyAddin : AddIn
    {
        public static MyAddin Addin = null;

        private MyAddin(System.IntPtr mdlDesc) : base(mdlDesc)
        {
            Addin = this;
        }

        protected override int Run(string[] commandLine)
        {
            MessageBox.Show("Hello World!");
            return 0;
        }
    }
}

The .NET assembly must meet the following three conditions for it to run as Add-in under MicroStation:

It contains a class derived from Bentley.MstnPlatformNET.AddIn.
The derived class must provide a single-argument constructor (MDL descriptor of type IntPtr),
and this constructor must be linked to the base class constructor.
The derived class must override the virtual method Run() in the Add-in based class.

Build Solution

Under menus, select Build > Build Solution to compile the solution.

When you see the following information in the VS output window, it means you have

successfully created an MicroStation Add-in.

========== Build All: 1 succeeded, 0 failed, 0 skipped ==========

If you unfortunately see a message as

========== Build All: 0 succeeded, x failed ==========

Checking the error descriptions in the output window can help you identify the problem.

Run your Add-in program

Launch/Open MicroStation, open the “key-in” window (or apply the F9 shortcut)

Key-in “mdl load csAddins” in the input field and press Enter.

A message box with "Hello World!" message is loaded.

We have successfully created and loaded our first Add-in.

You can download the source code for this wiki here.

If you plan to create similar projects in the future, consider turning this project into a Visual Studio template. This allows you to quickly create new projects with the same structure, settings, and references already in place. Check out the following link for detailed instructions on how to create and use a Visual Studio project template.

Create project templates.

Prev: Introduction and Prerequisite

Next: Creating Elements in Add-in