CsvHelper

写66666行两个数字 用CsvHelper里的ExcelSerializer 400ms SaveAs 200ms 共600ms 直接用StreamWriter 150ms
行数可以超过65536
worksheet reader

 class Program
    {
        static void Main(string[] args)
        {
            XLWorkbook workbook = new XLWorkbook("E://233.xlsx",XLEventTracking.Disabled);
            var sheet = workbook.Worksheets.First(p => p.Name == "ABC");
            var csv = new CsvReader(new ExcelParser(sheet));
            csv.Configuration.RegisterClassMap<MapA>();
            var records=csv.GetRecords<A>();
            foreach(var re in records)
            {
                Console.WriteLine(re.ToString());
            }
            foreach (var header in csv.FieldHeaders)
            {
                Console.WriteLine(header);
            }
        }
        public class MapA:CsvClassMap<A>
        {
            public MapA()
            {
                Map(m=>m.a).Name("AAA");
                Map(m=>m.b).Name("BBB");
            }   
        }
        public static List<A> list = new List<A> { new A(1, 2), new A(3, 4) };
        public class A
        {
            public int a
            {
                get; set;
            }
            public int b
            {
                get; set;
            }
            public A() { }
            public A(int a,int b)
            {
                this.a = a;
                this.b = b;
            }
            public override string ToString()
            {
                return a + " " + b;
            }
        }
    }

worksheet writer

 class Program
    {
        static void Main(string[] args)
        {
            XLWorkbook workbook = new XLWorkbook(XLEventTracking.Disabled);
            var sheet = workbook.AddWorksheet("ABC");
            var csv = new CsvWriter(new ExcelSerializer(sheet));
            csv.Configuration.RegisterClassMap<MapA>();
            csv.WriteHeader<A>();
            csv.WriteRecords(list);
            workbook.SaveAs("E://233.xlsx");
        }
        public class MapA:CsvClassMap<A>
        {
            public MapA()
            {
                Map(m=>m.a).Name("AAA");
                Map(m=>m.b).Name("BBB");
            }   
        }
        public static List<A> list = new List<A> { new A(1, 2), new A(3, 4) };
        public class A
        {
            public int a
            {
                get; set;
            }
            public int b
            {
                get; set;
            }
            public A() { }
            public A(int a,int b)
            {
                this.a = a;
                this.b = b;
            }
        }
    }

Writer

class Program
    {
        static void Main(string[] args)
        {
            FileStream file = new FileStream("E://123.csv", FileMode.Open);
            StreamWriter writer = new StreamWriter(file, Encoding.UTF8);
            var csv = new CsvWriter(writer);
            csv.Configuration.RegisterClassMap<MyClassMap>();
            csv.WriteHeader<A>();
            csv.WriteRecords(list);
            writer.Flush();
            writer.Close();
        }
        public class MyClassMap : CsvClassMap<A>
        {
            public MyClassMap()
            {
                Map(m => m.a).Name("AAA");
                Map(m => m.b).Name("BBB");
                Map(m => m.c);
            }
        }
        public static List<A> list = new List<A>() { new A(1, 2, 3), new A(4, 5, 6) };

        public class A
        {
            public A() { }
            public int a
            {
                get; set;
            }
            public int b
            {
                get; set;
            }
            public int c
            {
                get; set;
            }
            public A(int a,int b,int c)
            {
                this.a = a;
                this.b = b;
                this.c = c;
            }
            public override string ToString()
            {
                return a + " " + b + " " + c;
            }
        }
    }

Reader

    class Program
    {
        static void Main(string[] args)
        {
            FileStream file = new FileStream("E://123.csv", FileMode.Open);
            StreamReader reader = new StreamReader(file, Encoding.UTF8);
            var csv = new CsvReader(reader);
            csv.Configuration.RegisterClassMap<MyClassMap>();
            var records=csv.GetRecords<A>();
            foreach(var re in records)
            {
                //GetRecords在foreach里会自动调用Read()，GetRecord要手动调用Read()
                Console.WriteLine(re.ToString());
                Console.WriteLine(csv.GetField("BBB"));
                Console.WriteLine(csv.GetField(1));
            }
            var headers = csv.FieldHeaders;//调用过Read()才能获取header
            reader.Close();
            file.Close();
        }
        public class MyClassMap : CsvClassMap<A>
        {
            public MyClassMap()
            {
                Map(m => m.a).Name("AAA");
                Map(m => m.b).Name("BBB");
                Map(m => m.c);
            }
        }
        public static List<A> list = new List<A>() { new A(1, 2, 3), new A(4, 5, 6) };

        public class A
        {
            public A() { }
            public int a
            {
                get; set;
            }
            public int b
            {
                get; set;
            }
            public int c
            {
                get; set;
            }
            public A(int a,int b,int c)
            {
                this.a = a;
                this.b = b;
                this.c = c;
            }
            public override string ToString()
            {
                return a + " " + b + " " + c;
            }
        }
    }