I saw two common approaches for coding standards for private member variables:

class Foo
{
    private int _i;
    private string _id;     
}


and 

class Foo
{
    private int m_i;
    private string m_id; 
}

I believe the latter is coming from C++. Also, many people specify type before the member variable: double m_dVal -- to indicate that is is a nonconstant member variable of the type double?

What are the conventions in C#?