SUO File in .NET Visual Studio Projects
The solution user options (.suo) file is a structured storage, or compound, file stored in a binary format. You save user information into streams with the name of the stream being the key that will be used to identify the information in the .suo file. (as per Microsoft Documentation)
What information does the suo file contain?
A Solution user option file, is a binary file, which is specific to a given user, and is not version controlled. The .suo files contain user dependant information, like the state of the solution explorer and your last configuration settings like:
1. Visual Studio TABS Information
What tabs you left open the last time you worked on the project in visual studio, so those tabs are open again when you reload the project in Visual Studio. So, suo files track which windows were open when the solution was closed and opens those again when visual studio is again opened.
2. Breakpoint Information and Watch Window Settings
suo file also contains all your breakpoints. When you debug your project next time when you load visual studio, same breakpoints are hit again.
3. Information about startup project
If in your solution, you have more than one projects and you have made one of the project as startup project, suo file will contain that information in it. Next time when you run the visual studio, you will see the same project is set as startup project.
Problems with suo files:
Sometimes the suo file gets so large which affects the performance of visual studio and visual studio becomes slow and starts hanging. In such scenarios, you must delete suo file from your project.