C# 抽象类和接口的使用

1.设计原则

1.1 单一职责原则

不要存在多于一个导致类变更的原因。通俗的说，即一个类只负责一项职责。（代码级别，方法级别，类的级别）

1.2 里氏替换原则

所有引用基类的地方必须能透明地使用其子类的对象。（不要重写父类的方法，不使用virtual关键字）

1.3 依赖倒置原则

高层模块不应该依赖低层模块，二者都应该依赖其抽象；抽象不应该依赖细节；细节应该依赖抽象。（多使用抽象类和接口） 

1.4 接口隔离原则

客户端不应该依赖它不需要的接口；一个类对另一个类的依赖应该建立在最小的接口上。（接口不要包含太多方法）         

1.5 迪米特法则

一个对象应该对其他对象保持最少的了解。（只与直接的朋友通信）出现成员变量、方法参数、方法返回值中的类为直接朋友关系，而出现在局部变量中的类则不是直接的朋友关系

1.6 开闭原则

一个软件实体如类、模块和函数应该对扩展开放，对修改关闭。

2.类和类之间的关系

组合，聚合，关联，依赖

 链接

3.一个功能设计的演变

3.1 组织信息导出

public class OrganizationExcel
    {
        public void Export()
        {
            using (FileStream fs = new FileStream("d:/1.xlsx", FileMode.OpenOrCreate))
            {
                string[] HeaderNameList = { "组织名称", "所属公司", "组织类型", "组织类别", "党委部室", "支部地址", "书记名" };

                IWorkbook workbook = new XSSFWorkbook();
                ICellStyle cellStyle = GetHeadCellStyle(workbook);
                ISheet sheet = workbook.CreateSheet("sheet1");
                IRow headerRow = sheet.CreateRow(0);

                for (int i = 0; i < HeaderNameList.Length; i++)
                {
                    ICell cell = headerRow.CreateCell(i);
                    cell.SetCellValue(HeaderNameList[i]);
                    cell.CellStyle = cellStyle;
                }

                for (int i = 1; i < 10; i++)
                {
                    IRow dataRow = sheet.CreateRow(i);
                    dataRow.CreateCell(0).SetCellValue($"组织{i}");
                    dataRow.CreateCell(1).SetCellValue($"公司{i}");
                    dataRow.CreateCell(2).SetCellValue($"类型{i}");
                    dataRow.CreateCell(3).SetCellValue($"类别{i}");
                    dataRow.CreateCell(4).SetCellValue($"党委部室{i}");
                    dataRow.CreateCell(5).SetCellValue($"支部地址{i}");
                    dataRow.CreateCell(6).SetCellValue($"书记名{i}");
                }

                workbook.Write(fs);
            }
        }

        protected ICellStyle GetHeadCellStyle(IWorkbook workbook)
        {
            ICellStyle style = workbook.CreateCellStyle();
            style.FillPattern = FillPattern.SolidForeground;
            style.FillForegroundColor = NPOI.HSSF.Util.HSSFColor.Grey25Percent.Index;
            return style;
        }
    }

3.2 增加对人员的导出

public abstract class BaseExcel
    {

        /// <summary>
        /// 导出
        /// </summary>
        public void Export()
        {
            using (FileStream fs = new FileStream("d:/1.xlsx", FileMode.OpenOrCreate))
            {
                IWorkbook workbook = new XSSFWorkbook();
                ICellStyle cellStyle = GetHeadCellStyle(workbook);
                ISheet sheet = workbook.CreateSheet("sheet1");
                IRow headerRow = sheet.CreateRow(0);

                for (int i = 0; i < HeaderNameList.Length; i++)
                {
                    ICell cell = headerRow.CreateCell(i);
                    cell.SetCellValue(HeaderNameList[i]);
                    cell.CellStyle = cellStyle;
                }

                SetDataRow(sheet);

                workbook.Write(fs);
            }
        }
        /// <summary>
        /// 表头数组
        /// </summary>
        public abstract string[] HeaderNameList { get; }

        /// <summary>
        /// 设置每一列的数据值
        /// </summary>
        public abstract Action<ISheet> SetDataRow { get; }

        protected ICellStyle GetHeadCellStyle(IWorkbook workbook)
        {
            ICellStyle style = workbook.CreateCellStyle();
            style.FillPattern = FillPattern.SolidForeground;
            style.FillForegroundColor = NPOI.HSSF.Util.HSSFColor.Grey25Percent.Index;
            return style;
        }
    }

class OrganizationExcel : BaseExcel
    {
        public override string[] HeaderNameList { get { return new string[] { "组织名称", "所属公司", "组织类型", "组织类别", "党委部室", "支部地址", "书记名" }; } }

        public override Action<ISheet> SetDataRow =>
            (sheet) =>
            {
                for (int i = 1; i < 10; i++)
                {
                    IRow dataRow = sheet.CreateRow(i);
                    dataRow.CreateCell(0).SetCellValue($"组织{i}");
                    dataRow.CreateCell(1).SetCellValue($"公司{i}");
                    dataRow.CreateCell(2).SetCellValue($"类型{i}");
                    dataRow.CreateCell(3).SetCellValue($"类别{i}");
                    dataRow.CreateCell(4).SetCellValue($"党委部室{i}");
                    dataRow.CreateCell(5).SetCellValue($"支部地址{i}");
                    dataRow.CreateCell(6).SetCellValue($"书记名{i}");
                }
            };
    }

class PersonnelExcel : BaseExcel
    {
        public override string[] HeaderNameList { get { return new string[] { "人员名", "人员登录名", "人员组织", "人员类型"}; } }

        public override Action<ISheet> SetDataRow =>
            (sheet) =>
            {
                for (int i = 1; i < 10; i++)
                {
                    IRow dataRow = sheet.CreateRow(i);
                    dataRow.CreateCell(0).SetCellValue($"人员名{i}");
                    dataRow.CreateCell(1).SetCellValue($"人员登录名{i}");
                    dataRow.CreateCell(2).SetCellValue($"人员组织{i}");
                    dataRow.CreateCell(3).SetCellValue($"人员类型{i}");
                }
            };
    }

3.3 增加对责任矩阵的excel导出

public abstract class BaseExcel
    {

        /// <summary>
        /// 导出
        /// </summary>
        public void Export()
        {
            using (FileStream fs = new FileStream("d:/1.xlsx", FileMode.OpenOrCreate))
            {
                var workbook = GetWorkBook("sheet1");
                workbook.Write(fs);
            }
        }
        protected abstract IWorkbook GetWorkBook(string sheetName);
    }

public abstract class BaseOrdinaryExcel : BaseExcel
    {
        /// <summary>
        /// 表头数组
        /// </summary>
        public abstract string[] HeaderNameList { get; }

        /// <summary>
        /// 设置DataRow
        /// </summary>
        public abstract Action<ISheet> SetDataRow { get; }

        /// <summary>
        /// 获取excel对象
        /// </summary>
        /// <param name="sheetName">sheet名</param>
        /// <returns></returns>
        protected override IWorkbook GetWorkBook(string sheetName)
        {
            IWorkbook workbook = new XSSFWorkbook();
            ICellStyle cellStyle = GetHeadCellStyle(workbook);
            ISheet sheet = workbook.CreateSheet(sheetName);
            IRow headerRow = sheet.CreateRow(0);

            for (int i = 0; i < HeaderNameList.Length; i++)
            {
                ICell cell = headerRow.CreateCell(i);
                cell.SetCellValue(HeaderNameList[i]);
                cell.CellStyle = cellStyle;
            }

            SetDataRow(sheet);

            return workbook;
        }


        protected ICellStyle GetHeadCellStyle(IWorkbook workbook)
        {
            ICellStyle style = workbook.CreateCellStyle();
            style.FillPattern = FillPattern.SolidForeground;
            style.FillForegroundColor = NPOI.HSSF.Util.HSSFColor.Grey25Percent.Index;
            return style;
        }

    }

class OrganizationExcel : BaseOrdinaryExcel
    {
        public override string[] HeaderNameList { get { return new string[] { "组织名称", "所属公司", "组织类型", "组织类别", "党委部室", "支部地址", "书记名" }; } }

        public override Action<ISheet> SetDataRow =>
            (sheet) =>
            {
                for (int i = 1; i < 10; i++)
                {
                    IRow dataRow = sheet.CreateRow(i);
                    dataRow.CreateCell(0).SetCellValue($"组织{i}");
                    dataRow.CreateCell(1).SetCellValue($"公司{i}");
                    dataRow.CreateCell(2).SetCellValue($"类型{i}");
                    dataRow.CreateCell(3).SetCellValue($"类别{i}");
                    dataRow.CreateCell(4).SetCellValue($"党委部室{i}");
                    dataRow.CreateCell(5).SetCellValue($"支部地址{i}");
                    dataRow.CreateCell(6).SetCellValue($"书记名{i}");
                }
            };
    }

class PersonnelExcel : BaseOrdinaryExcel
    {
        public override string[] HeaderNameList { get { return new string[] { "人员名", "人员登录名", "人员组织", "人员类型"}; } }

        public override Action<ISheet> SetDataRow =>
            (sheet) =>
            {
                for (int i = 1; i < 10; i++)
                {
                    IRow dataRow = sheet.CreateRow(i);
                    dataRow.CreateCell(0).SetCellValue($"人员名{i}");
                    dataRow.CreateCell(1).SetCellValue($"人员登录名{i}");
                    dataRow.CreateCell(2).SetCellValue($"人员组织{i}");
                    dataRow.CreateCell(3).SetCellValue($"人员类型{i}");
                }
            };
    }

public class ResponsibilityTableExcel : BaseExcel
    {
        ICellStyle headCellStyle;

        private const int
            ORGAN_ROW_NO = 0,               //组织行
            PERSONNEL_NAME_ROW_NO = 1;      //人员名行 

        protected override IWorkbook GetWorkBook(string sheetName)
        {

            IWorkbook workbook = new XSSFWorkbook();
            headCellStyle = GetHeadCellStyle(workbook);
            ISheet sheet = workbook.CreateSheet(sheetName);

            IRow organizationRow = sheet.CreateRow(ORGAN_ROW_NO);
            ICell cell = organizationRow.CreateCell(0);
            SetHeadValue(cell, "矩阵名");
            cell = organizationRow.CreateCell(1);
            SetHeadValue(cell, "组织名");
            sheet.AddMergedRegion(new CellRangeAddress(ORGAN_ROW_NO, ORGAN_ROW_NO, 1, 3));

            IRow personnelNameRow = sheet.CreateRow(PERSONNEL_NAME_ROW_NO);
            for (int i = 1; i < 4; i++)
            {
                cell = personnelNameRow.CreateCell(i);
                SetHeadValue(cell, $"人员{i}");
            }
            sheet.AddMergedRegion(new CellRangeAddress(ORGAN_ROW_NO, PERSONNEL_NAME_ROW_NO, 0, 0));

            return workbook;
        }

        private void SetHeadValue(ICell cell, string value)
        {
            cell.SetCellValue(value);
            cell.CellStyle = headCellStyle;
        }

        private ICellStyle GetHeadCellStyle(IWorkbook workbook)
        {
            ICellStyle style = workbook.CreateCellStyle();
            style.Alignment = HorizontalAlignment.Center;
            style.VerticalAlignment = VerticalAlignment.Center;
            return style;
        }
    }

3.4 抽象出接口

public interface IExport
    {
        void Export();
    }

    abstract class BaseExcel : IExport
    {

        /// <summary>
        /// 导出
        /// </summary>
        public void Export()
        {
            using (FileStream fs = new FileStream("d:/1.xlsx", FileMode.OpenOrCreate))
            {
                var workbook = GetWorkBook("sheet1");
                workbook.Write(fs);
            }
        }
        protected abstract IWorkbook GetWorkBook(string sheetName);
    }

abstract class BaseOrdinaryExcel : BaseExcel
    {
        /// <summary>
        /// 表头数组
        /// </summary>
        public abstract string[] HeaderNameList { get; }

        /// <summary>
        /// 设置DataRow
        /// </summary>
        public abstract Action<ISheet> SetDataRow { get; }

        /// <summary>
        /// 获取excel对象
        /// </summary>
        /// <param name="sheetName">sheet名</param>
        /// <returns></returns>
        protected override IWorkbook GetWorkBook(string sheetName)
        {
            IWorkbook workbook = new XSSFWorkbook();
            ICellStyle cellStyle = GetHeadCellStyle(workbook);
            ISheet sheet = workbook.CreateSheet(sheetName);
            IRow headerRow = sheet.CreateRow(0);

            for (int i = 0; i < HeaderNameList.Length; i++)
            {
                ICell cell = headerRow.CreateCell(i);
                cell.SetCellValue(HeaderNameList[i]);
                cell.CellStyle = cellStyle;
            }

            SetDataRow(sheet);

            return workbook;
        }


        protected ICellStyle GetHeadCellStyle(IWorkbook workbook)
        {
            ICellStyle style = workbook.CreateCellStyle();
            style.FillPattern = FillPattern.SolidForeground;
            style.FillForegroundColor = NPOI.HSSF.Util.HSSFColor.Grey25Percent.Index;
            return style;
        }

    }

 class OrganizationExcel : BaseOrdinaryExcel
    {
        public override string[] HeaderNameList { get { return new string[] { "组织名称", "所属公司", "组织类型", "组织类别", "党委部室", "支部地址", "书记名" }; } }

        public override Action<ISheet> SetDataRow =>
            (sheet) =>
            {
                for (int i = 1; i < 10; i++)
                {
                    IRow dataRow = sheet.CreateRow(i);
                    dataRow.CreateCell(0).SetCellValue($"组织{i}");
                    dataRow.CreateCell(1).SetCellValue($"公司{i}");
                    dataRow.CreateCell(2).SetCellValue($"类型{i}");
                    dataRow.CreateCell(3).SetCellValue($"类别{i}");
                    dataRow.CreateCell(4).SetCellValue($"党委部室{i}");
                    dataRow.CreateCell(5).SetCellValue($"支部地址{i}");
                    dataRow.CreateCell(6).SetCellValue($"书记名{i}");
                }
            };
    }

    class PersonnelExcel : BaseOrdinaryExcel
    {
        public override string[] HeaderNameList { get { return new string[] { "人员名", "人员登录名", "人员组织", "人员类型"}; } }

        public override Action<ISheet> SetDataRow =>
            (sheet) =>
            {
                for (int i = 1; i < 10; i++)
                {
                    IRow dataRow = sheet.CreateRow(i);
                    dataRow.CreateCell(0).SetCellValue($"人员名{i}");
                    dataRow.CreateCell(1).SetCellValue($"人员登录名{i}");
                    dataRow.CreateCell(2).SetCellValue($"人员组织{i}");
                    dataRow.CreateCell(3).SetCellValue($"人员类型{i}");
                }
            };
    }

class ResponsibilityTableExcel : BaseExcel
    {
        ICellStyle headCellStyle;

        private const int
            ORGAN_ROW_NO = 0,               //组织行
            PERSONNEL_NAME_ROW_NO = 1;      //人员名行 

        protected override IWorkbook GetWorkBook(string sheetName)
        {

            IWorkbook workbook = new XSSFWorkbook();
            headCellStyle = GetHeadCellStyle(workbook);
            ISheet sheet = workbook.CreateSheet(sheetName);

            IRow organizationRow = sheet.CreateRow(ORGAN_ROW_NO);
            ICell cell = organizationRow.CreateCell(0);
            SetHeadValue(cell, "矩阵名");
            cell = organizationRow.CreateCell(1);
            SetHeadValue(cell, "组织名");
            sheet.AddMergedRegion(new CellRangeAddress(ORGAN_ROW_NO, ORGAN_ROW_NO, 1, 3));

            IRow personnelNameRow = sheet.CreateRow(PERSONNEL_NAME_ROW_NO);
            for (int i = 1; i < 4; i++)
            {
                cell = personnelNameRow.CreateCell(i);
                SetHeadValue(cell, $"人员{i}");
            }
            sheet.AddMergedRegion(new CellRangeAddress(ORGAN_ROW_NO, PERSONNEL_NAME_ROW_NO, 0, 0));

            return workbook;
        }

        private void SetHeadValue(ICell cell, string value)
        {
            cell.SetCellValue(value);
            cell.CellStyle = headCellStyle;
        }

        private ICellStyle GetHeadCellStyle(IWorkbook workbook)
        {
            ICellStyle style = workbook.CreateCellStyle();
            style.Alignment = HorizontalAlignment.Center;
            style.VerticalAlignment = VerticalAlignment.Center;
            return style;
        }
    }

class OrganizationTxt : IExport
    {
        public void Export()
        {
            FileStream fs = new FileStream("d:/1.txt", FileMode.Create);
            StreamWriter sw = new StreamWriter(fs);

            string[] header = new string[] { "组织名称", "所属公司", "组织类型", "组织类别", "党委部室", "支部地址", "书记名" };
            sw.WriteLine(string.Join(" ", header));

            List<string> list = new List<string>();
            for (int i = 1; i < 10; i++)
            {
                list.Add($"组织{i}");
                list.Add($"公司{i}");
                list.Add($"类型{i}");
                list.Add($"类别{i}");
                list.Add($"党委部室{i}");
                list.Add($"支部地址{i}");
                list.Add($"书记名{i}");
                sw.WriteLine(string.Join(" ", list));
                list.Clear();
            }

            sw.Flush();
            //关闭流
            sw.Close();
            fs.Close();
        }
    }

3.5 结论

在这种设计中实现类既可以继承实现YourServiceBase ，也可以直接实现IYourService，提供了很好的灵活性。