C# list find duplicates

- C# list find duplicates by multiple property
- C# list find duplicates by property
- C# list string find duplicates
- C# list of strings find duplicates
- C# find duplicates in list of objects
- C# list object find duplicates
- C# find duplicates in list without linq
- C# find duplicates in list based on property
- C# find duplicates in list of objects and remove
- C# lambda find duplicates in list