Naming convention - underscore in C++ and C# variables

Question

It\'s common to see a _var variable name in a class field. What does the underscore mean? Is there a reference for all these special naming conventions?

Answer 1

Old question, new answer (C#).

Another use of underscores for C# is with ASP NET Core's DI (dependency injection). Private readonly variables of a class which got assigned to the injected interface during construction should start with an underscore. I guess it's a debate whether to use underscore for every private member of a class (although Microsoft itself follows it) but this one is certain.

private readonly ILogger _logger;

public MyDependency(ILogger logger)
{
    _logger = logger;
}