//修改前
namespace CleanCSharp.Errors.Dirty
{
    public class SomeClass
    {
        public int DoSomeProcess(int? id)
        {
            if (id == null)
            {
                return -1; // null id
            }
            string data =http://www.mamicode.com/ LoadData();
            if (string.IsNullOrWhiteSpace(data))
            {
                return -2; // data is corrupt
            }
            ProcessData(data);

            return 0; // no error, all good
        }
        private string LoadData()
        {
            return "some data";
        }
        private void ProcessData(string data)
        {
            // do something
        }
    }
}

修改前，调用
namespace CleanCSharp.Errors.Dirty
{
    public class ConsumerOfSomeClass
    {
        public void Consume()
        {
            var sc = new SomeClass();
            const int idToProcess = 42;
            int returnCode = sc.DoSomeProcess(idToProcess);
            switch (returnCode)
            {
                case -1: // null id
                         // do something
                 
            break;
                case -2: // corrupt data
                         // do something
                    break;
                case 0: // no error
                    Save(idToProcess);
                    break;
            }
        }
        private void Save(int id)
        {
            // save
        }
    }
}

//修改后
using System;
using System.IO;
namespace CleanCSharp.Errors.Clean
{
    public class SomeClass
    {
        public void DoSomeProcess(int? id)
        {
            if (id == null)
            {
                throw new ArgumentNullException("id");
            }
            string data =http://www.mamicode.com/ LoadData();
            ProcessData(data);
        }
        private string LoadData()
        {
            var demoData = http://www.mamicode.com/"";
            if (string.IsNullOrWhiteSpace(demoData))
            {
                throw new
                InvalidDataException(
                "The data stream contains no data.");
            }
            return demoData;
        }
        private void ProcessData(string data)
        {
            // do something
        }
    }
}

//修改后
using System;
using System.Diagnostics;
using System.IO;
namespace CleanCSharp.Errors.Clean
{
    public class ConsumerOfSomeClass
    {
        public void Consume()
        {
            var sc = new SomeClass();
            const int idToProcess = 42;
            try
            {
                sc.DoSomeProcess(idToProcess);
            }
            catch (ArgumentNullException ex)
            {
                // null id

                // do something such as logging
                // if cannot respond to this
                // exception propagate up the
                // call stack
                throw;
                // Notice the throw is not: throw ex;
            }
            catch (InvalidDataException ex)
            {
                // bad data
                // do something
                throw;
            }
            catch (Exception ex)
            {
                // any other exceptions that may occur
                // do something
                throw;
            }
            Save(idToProcess);
        }
        private void Save(int id)
        {
            // save
        }
    }

}