.net core使用Html模板转PDF文件并下载的业务类封装

　　前言：我这里文件下载的模板选型优先考虑html模板，上手容易，前后端通用，有了模板后就需要有转换了，html转PDF采用第三方包：SelectPdf，下面是代码核心类：

　　1-PDFService:

using Microsoft.AspNetCore.Hosting;
using SelectPdf;

namespace MeShop.Domain.PDF
{
    /// <summary>
    /// PDF业务类
    /// </summary>
    public class PDFService
    {
        private readonly IHostingEnvironment hostingEnvironment;

        public PDFService(IHostingEnvironment hostingEnvironment)
        {
            this.hostingEnvironment = hostingEnvironment;
        }


        /// <summary>
        /// 将Html替换参数后转成PDF字节流
        /// </summary>
        /// <param name="htmlFilePath">html模板文件路径</param>
        /// <param name="saveFileName">PDF文件名</param>
        /// <param name="replaceParamDic">变量替换字典</param>
        /// <returns></returns>
        public async Task<string> HtmlToPDFFile(string htmlFilePath, string saveFileName, Dictionary<string, string> replaceParamDic)
        {
            HtmlToPdf Renderer = new HtmlToPdf();
            //设置Pdf参数
            //设置页面方式-横向  PdfPageOrientation.Portrait  竖向
            Renderer.Options.PdfPageOrientation = PdfPageOrientation.Landscape;
            //设置页面大小，30种页面大小可以选择
            Renderer.Options.PdfPageSize = PdfPageSize.A4;
            //上下左右边距设置  
            Renderer.Options.MarginTop = 10;
            Renderer.Options.MarginBottom = 10;
            Renderer.Options.MarginLeft = 10;
            Renderer.Options.MarginRight = 10;

            //设置更多额参数可以去HtmlToPdfOptions里面选择设置
            //根据html内容导出PDF
            string docHtml = await File.ReadAllTextAsync(htmlFilePath, Encoding.UTF8);
            foreach (var item in replaceParamDic)
            {
                docHtml = docHtml.Replace(item.Key, item.Value);
            }

            PdfDocument pdfDocument = Renderer.ConvertHtmlString(docHtml);
            string saveFilePath = @$"{this.hostingEnvironment.ContentRootPath}\staticfiles\Download\{saveFileName}";
            if (File.Exists(saveFilePath))
            {
                File.Delete(saveFilePath);
            }
            pdfDocument.Save(saveFilePath);

            return saveFilePath;
        }

        /// <summary>
        /// 读取文件字节流
        /// </summary>
        /// <param name="filePath">资源文件（包含路径）</param>
        /// <param name="isDeleteSourceFile">是否删除资源文件</param>
        /// <returns></returns>
        public async Task<byte[]> GetByteByFile(string? filePath, bool isDeleteSourceFile = false)
        {
            byte[]? myByteArray = null;
            if (filePath != null && File.Exists(filePath))
            {
                using (FileStream fileStream = new FileStream(filePath, FileMode.Open))
                {
                    fileStream.Seek(0, SeekOrigin.Begin);
                    myByteArray = new byte[fileStream.Length];
                    await fileStream.ReadAsync(myByteArray, 0, (int)fileStream.Length);
                }
                if (isDeleteSourceFile)
                {
                    File.Delete(filePath);
                }
            }

            return myByteArray ?? new byte[0];
        }


        /// <summary>
        /// 压缩多个文件为zip文件
        /// </summary>
        /// <param name="zipFileName">zip压缩文件名</param>
        /// <param name="filePaths">资源文件列表（包含路径）</param>
        /// <param name="isDeleteSourceFile">是否删除资源文件</param>
        /// <returns></returns>
        public string CompressFileToZip(string zipFileName, string[] filePaths, bool isDeleteSourceFile = false)
        {
            string? zipFilePath = null;
            if (!string.IsNullOrWhiteSpace(zipFileName) && filePaths.Length > 0)
            {
                string zipDirectoryPath = @$"{this.hostingEnvironment.ContentRootPath}\staticfiles\Download\{DateTime.Now.ToString("yyyyMMddHHmmssfff")}";
                if (!Directory.Exists(zipDirectoryPath))
                {
                    Directory.CreateDirectory(zipDirectoryPath);
                }

                zipFilePath = @$"{this.hostingEnvironment.ContentRootPath}\staticfiles\Download\{zipFileName}";
                if (File.Exists(zipFilePath))
                {
                    File.Delete(zipFilePath);
                }

                foreach (var filePath in filePaths)
                {
                    string? fileName = filePath.Split('\\').LastOrDefault();
                    string copyFilePath = @$"{zipDirectoryPath}\{fileName}";
                    if (isDeleteSourceFile)
                    {
                        File.Move(filePath, copyFilePath);
                    }
                    else
                    {
                        File.Copy(filePath, copyFilePath);
                    }
                }
                CompressionHelper.Compression(zipDirectoryPath, zipFilePath);

                //压缩完成后，删除压缩使用文件夹及其子项
                Directory.Delete(zipDirectoryPath, true);
            }
            return zipFilePath ?? "";
        }
    }
}

　　　2-控制器方法示例：

[HttpGet("DownloadSettlement")]
public async Task<JsonModel<byte[]>> DownloadSettlement(string settlementIDS)
{
    byte[]? byteArray = null;
    string[] settlementIDArray = settlementIDS.Split(',');

    string templateHtmlPath = @$"{this.hostingEnvironment.ContentRootPath}\staticfiles\agentusersettlement.html";
    List<string> zipSaveFilePathList = new List<string>(settlementIDArray.Length);

    Base_shop baseShop = await this.shopService.GetBaseShopAsync();
    foreach (var item in settlementIDArray)
    {
        long settlementID = TypeParseHelper.StrToInt64(item);
        ResponseAgentUserSettlementDetail? detail = await this.agentUserSettlementService.GetDetailAsync(settlementID);
        if (detail != null)
        {
            Agent_user agentUser = await this.agentUserService.GetAsync(detail.AgentUserID) ?? new Agent_user();

            Dictionary<string, string> replaceDic = new Dictionary<string, string>()
            {
                {"@InvoiceNumber@",$"{detail.UpdateTime.ToString("yyyyMMdd")}{detail.ID}" },
                {"@UpdateTime@",$"{detail.UpdateTime.ToString("yyyyMMdd")}" },
                {"@AgentUserCompanyName@",$"{agentUser.CompanyName}" },
                {"@AgentUserCompanyAddress@",$"{agentUser.CompanyAddress}" },
                {"@BeginDate@",$"{detail.BeginDate.ToString("yyyy/MM/dd")}" },
                {"@EndDate@",$"{detail.EndDate.ToString("yyyy/MM/dd")}" },
                {"@TotalPoint@",$"{detail.TotalPoint.ToString("F3")}" },
                {"@AccountCompanyName@",$"{baseShop.CompanyName}" },
                {"@AccountCompanyAddress@",$"{baseShop.CompanyAddress}" },
                {"@AccountEmail@",$"{baseShop.ServiceEmail}" }
            };

            zipSaveFilePathList.Add(await this.pdfService.HtmlToPDFFile(templateHtmlPath, $"{settlementID}.pdf", replaceDic));

            //设置导出状态
            await this.agentUserSettlementService.SetExportStateAsync(settlementID, (int)EState.启用);
        }
    }

    if (zipSaveFilePathList.Count == 1)
    {
        byteArray = await this.pdfService.GetByteByFile(zipSaveFilePathList.FirstOrDefault());
    }
    else
    {
        string zipFilePath = this.pdfService.CompressFileToZip($"{settlementIDS.Replace(',', '_')}.zip", zipSaveFilePathList.ToArray(), true);
        byteArray = await this.pdfService.GetByteByFile(zipFilePath);
    }

    return base.SuccessResult(byteArray ?? new byte[0]);
}

　　3-前台JS下载文件字节流示例：

<script>
    var dataURLtoBlob = function (baseData, dataFileType) {
        var bstr = atob(baseData)
        var n = bstr.length;
        var u8arr = new Uint8Array(n);
        while (n--) {
            u8arr[n] = bstr.charCodeAt(n);
        }
        return new Blob([u8arr], { type: dataFileType });
    };

    var dataByteArray = "后台方法返回的文件字节流数据"
    var dataIsZip = true;
    var dataIsPDF = false

    var fileName = null;
    var blob = null;
    if (dataIsZip) {
        blob = dataURLtoBlob(dataByteArray, "application/zip; charset=utf-8");
        fileName = "test.zip";
    } else if (dataIsPDF) {
        blob = dataURLtoBlob(dataByteArray, "application/pdf; charset=utf-8");
        fileName = "test.pdf";
    }
    var url = window.URL.createObjectURL(blob);
    var a = document.createElement('a');
    a.href = url;
    a.download = fileName;
    a.click();
    window.URL.revokeObjectURL(url);
</script>