Developer Guide

Last updated Oct 30, 2025

Adding the external assembly `.dll` in UiPath Studio

Make sure you test the project for errors before attempting to build it.

From the Build menu, select Build Solution. The MathSquareOfSum.dll library is now built and saved in the following location:

%UserProfile%\source\repos\MathSquareOfSum\MathSquareOfSum\bin\Debug

Once the library is built, the Output panel should display a message as depicted below:

Creating the NuGet package

Launch NuGet Package Explorer and click Create a new package (Ctrl + N). A split-window is displayed which shows Package metadata and Package contents. We need to add all dependencies in the latter section.
Right-click inside the Package contents section. A context menu is displayed.
Select Add lib folder. Notice a new lib item is created in the Package contents section.
Right-click lib and select to Add Existing File….
Load the external assembly (.dll) created above. In our case, the MathSquareOfSum.dll file is located in the %UserProfile%\source\repos\MathSquareOfSum\MathSquareOfSum\bin\Debug folder.
With the file selected, access the Edit menu and select Edit Metadata. The left panel is now fitted with editable metadata fields.
Fill in the fields as you see fit to better describe your custom activity.
Fill in the Id field. In our case, it can be UiPath.MathSquare.Activities, where the first value, UiPath, stands for the team which created the package. If no particular team was involved, the first value can be left blank.
Select the green check mark button in the top-left corner of the Package metadata section to save all changes.
From the File menu, select Save As.... An explorer window shows up, allowing you to choose the location of the new file.
Save the file in the folder where local packages are stored by UiPath (C:\Program Files (x86)\UiPath\Studio\Packages in versions prior to 2021.4 or C:\Program Files\UiPath\Studio\Packages starting with version 2021.4). The UiPath.MathSquare.Activities.1.0.0.nupkg file is now created in the UiPath.MathSquare.Activities folder inside the packages folder.

Loading the NuGet package in Studio

Access the Package Manager from Studio.
Since we saved the NuGet package in the local packages folder, the activity should be available in the Local feed.
Search for the activity and click Install and then Save. The new activity is now installed and can be used in your automation projects.