<exception cref="member">description</exception>

// compile with: /doc:DocFileName.xml 

/// comment for class
public class EClass : System.Exception
{
    // class definition...
}

/// <exception cref="System.Exception">Thrown when...</exception>
class TestClass
{
    static void Main()
    {
        try
        {
        }
        catch (EClass)
        {
        }
    }
}