Hi Dean,
You can write all common methods in one class file and save this file as FileName.cs extension.
For example: Your saved file namespace is “CommonFile” and class name is “Utilities”.
Follow these below steps to your second solution file for adding above class file.
1. Right click on Solution file and select “Add” - > “Add Existing Item” and select above class file (FileName.cs).
2. Add a reference file to your code at the top by
Using <CommonFile>;
3. Inheritance your common file class using below code:
public class SecondClassName : Utilities
4. Add one line code in to the startup function as below
base.Init(thisXDocument, thisApplication, CultureInfo.CurrentCulture);
Note: The above code in C#