C# programming Excel import and export (source code download) (Part 1)

This article mainly introduces Excel import and export in C#.

1. Introduction

1.1 Third-party class library: NPOI

Description: NPOI is the .NET version of the POI project, which can be used Reading and writing operations of Excel and Word.

Advantages: No need to install Office environment.

Download address: http://npoi.codeplex.com/releases

1.2 Introduction to Excel structure

Workbook: Each Excel file can be understood as one work log.

Worksheet (Sheet): A workbook (Workbook) can contain multiple worksheets.

Row: A worksheet (Sheet) can contain multiple rows.

2. Excel import

2.1 Operation process

2.2 NPOI operation code

##Instructions: Convert Excel file to List

Steps:

①Read Excel file and initialize a workbook (Workbook);

② Get a worksheet (Sheet) from the workbook; the default is the first worksheet of the workbook;

③ Traverse All rows (rows) of the worksheet; by default, the traversal starts from the second row, and the first row (serial number 0) is the cell header;

④Traverse each cell (cell) of the row, according to a certain The rules assign values ​​to the properties of objects.

Code:

/// 从Excel2003取数据并记录到List集合里
/// <param name="cellHeard">单元头的Key和Value：{ { "UserName", "姓名" }, { "Age", "年龄" } };</param>
/// <param name="filePath">保存文件绝对路径</param>
/// <param name="errorMsg">错误信息</param>
/// <returns>转换好的List对象集合</returns>
private static List<T> Excel2003ToEntityList<T>(Dictionary<string, string> cellHeard, string filePath, out StringBuilder errorMsg) where T : new()
{
    errorMsg = new StringBuilder(); // 错误信息,Excel转换到实体对象时，会有格式的错误信息
    List<T> enlist = new List<T>(); // 转换后的集合
    List<string> keys = cellHeard.Keys.ToList(); // 要赋值的实体对象属性名称
    try
    {
        using (FileStream fs = File.OpenRead(filePath))
        {
            HSSFWorkbook workbook = new HSSFWorkbook(fs);
            HSSFSheet sheet = (HSSFSheet)workbook.GetSheetAt(0); // 获取此文件第一个Sheet页
            for (int i = 1; i <= sheet.LastRowNum; i++) // 从1开始，第0行为单元头
            {
                // 1.判断当前行是否空行，若空行就不在进行读取下一行操作，结束Excel读取操作
                if (sheet.GetRow(i) == null)
                {
                    break;
                }
                T en = new T();
                string errStr = ""; // 当前行转换时，是否有错误信息，格式为：第1行数据转换异常：XXX列；
                for (int j = 0; j < keys.Count; j++)
                {
                    // 2.若属性头的名称包含&#39;.&#39;,就表示是子类里的属性，那么就要遍历子类，eg：UserEn.TrueName
                    if (keys[j].IndexOf(".") >= 0)
                    {
                        // 2.1解析子类属性
                        string[] properotyArray = keys[j].Split(new string[] { "." }, StringSplitOptions.RemoveEmptyEntries);
                        string subClassName = properotyArray[0]; // &#39;.&#39;前面的为子类的名称
                        string subClassProperotyName = properotyArray[1]; // &#39;.&#39;后面的为子类的属性名称
                        System.Reflection.PropertyInfo subClassInfo = en.GetType().GetProperty(subClassName); // 获取子类的类型
                        if (subClassInfo != null)
                        {
                            // 2.1.1 获取子类的实例
                            var subClassEn = en.GetType().GetProperty(subClassName).GetValue(en, null);
                            // 2.1.2 根据属性名称获取子类里的属性信息
                            System.Reflection.PropertyInfo properotyInfo = subClassInfo.PropertyType.GetProperty(subClassProperotyName);
                            if (properotyInfo != null)
                            {
                                try
                                {
                                    // Excel单元格的值转换为对象属性的值，若类型不对，记录出错信息
                                    properotyInfo.SetValue(subClassEn, GetExcelCellToProperty(properotyInfo.PropertyType, sheet.GetRow(i).GetCell(j)), null);
                                }
                                catch (Exception e)
                                {
                                    if (errStr.Length == 0)
                                    {
                                        errStr = "第" + i + "行数据转换异常：";
                                    }
                                    errStr += cellHeard[keys[j]] + "列；";
                                }
                            }
                        }
                    }
                    else
                    {
                        // 3.给指定的属性赋值
                        System.Reflection.PropertyInfo properotyInfo = en.GetType().GetProperty(keys[j]);
                        if (properotyInfo != null)
                        {
                            try
                            {
                                // Excel单元格的值转换为对象属性的值，若类型不对，记录出错信息
                                properotyInfo.SetValue(en, GetExcelCellToProperty(properotyInfo.PropertyType, sheet.GetRow(i).GetCell(j)), null);
                            }
                            catch (Exception e)
                            {
                                if (errStr.Length == 0)
                                {
                                    errStr = "第" + i + "行数据转换异常：";
                                }
                                errStr += cellHeard[keys[j]] + "列；";
                            }
                        }
                    }
                }
                // 若有错误信息，就添加到错误信息里
                if (errStr.Length > 0)
                {
                    errorMsg.AppendLine(errStr);
                }
                enlist.Add(en);
            }
        }
        return enlist;
    }
    catch (Exception ex)
    {
        throw ex;
    }
}

2.3 C# logical operation code

Description: Perform subsequent operations on the Excel-converted List; such as: detect validity, persistent storage Wait

Steps:

①Call the 2.2 code to convert the Excel file to List.

② Check the validity of List: whether the required items are empty, whether there are duplicate records, etc.

③Perform persistent storage operation on List. Such as: stored in the database.

④返回操作结果。

代码：

public void ImportExcel(HttpContext context)
{
    StringBuilder errorMsg = new StringBuilder(); // 错误信息
    try
    {
        #region 1.获取Excel文件并转换为一个List集合
        // 1.1存放Excel文件到本地服务器
        HttpPostedFile filePost = context.Request.Files["filed"]; // 获取上传的文件
        string filePath = ExcelHelper.SaveExcelFile(filePost); // 保存文件并获取文件路径
 
        // 单元格抬头
        // key：实体对象属性名称，可通过反射获取值
        // value：属性对应的中文注解
        Dictionary<string, string> cellheader = new Dictionary<string, string> {
            { "Name", "姓名" },
            { "Age", "年龄" },
            { "GenderName", "性别" },
            { "TranscriptsEn.ChineseScores", "语文成绩" },
            { "TranscriptsEn.MathScores", "数学成绩" },
        };
 
        // 1.2解析文件，存放到一个List集合里
        List<UserEntity> enlist = ExcelHelper.ExcelToEntityList<UserEntity>(cellheader, filePath, out errorMsg);
 
        #endregion
 
        #region 2.对List集合进行有效性校验
 
        #region 2.1检测必填项是否必填
 
        for (int i = 0; i < enlist.Count; i++)
        {
            UserEntity en = enlist[i];
            string errorMsgStr = "第" + (i + 1) + "行数据检测异常：";
            bool isHaveNoInputValue = false; // 是否含有未输入项
            if (string.IsNullOrEmpty(en.Name))
            {
                errorMsgStr += "姓名列不能为空；";
                isHaveNoInputValue = true;
            }
            if (isHaveNoInputValue) // 若必填项有值未填
            {
                en.IsExcelVaildateOK = false;
                errorMsg.AppendLine(errorMsgStr);
            }
        }
 
        #endregion
 
        #region 2.2检测Excel中是否有重复对象
 
        for (int i = 0; i < enlist.Count; i++)
        {
            UserEntity enA = enlist[i];
            if (enA.IsExcelVaildateOK == false) // 上面验证不通过，不进行此步验证
            {
                continue;
            }
 
            for (int j = i + 1; j < enlist.Count; j++)
            {
                UserEntity enB = enlist[j];
                // 判断必填列是否全部重复
                if (enA.Name == enB.Name)
                {
                    enA.IsExcelVaildateOK = false;
                    enB.IsExcelVaildateOK = false;
                    errorMsg.AppendLine("第" + (i + 1) + "行与第" + (j + 1) + "行的必填列重复了");
                }
            }
        }
 
        #endregion
 
        // TODO：其他检测
 
        #endregion
 
        // 3.TODO：对List集合持久化存储操作。如：存储到数据库
         
        // 4.返回操作结果
        bool isSuccess = false;
        if (errorMsg.Length == 0)
        {
            isSuccess = true; // 若错误信息成都为空，表示无错误信息
        }
        var rs = new { success = isSuccess,  msg = errorMsg.ToString(), data = enlist };
        System.Web.Script.Serialization.JavaScriptSerializer js = new System.Web.Script.Serialization.JavaScriptSerializer();
        context.Response.ContentType = "text/plain";
        context.Response.Write(js.Serialize(rs)); // 返回Json格式的内容
    }
    catch (Exception ex)
    {
　　 　　throw ex;
    }
}

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