ASP.NET Core MVC导出PDF报错：无法加载PDF文档求解决方案

编写了将数据库表数据导出为PDF的C#代码，代码可正常执行，但下载生成的PDF文件时出现报错：
Error - failed to load PDF document

相关代码 #

私有方法getexportdata #

private void getexportdata()
{
            try
            {
                string sql = null;

                if (role == "BLC")
                {
                    sql = "select SurveyInformationId,AreaName,userinfo.EmployeeName,BranchName,SurveyDate,ManagerApprove,u.EmployeeName as manager from SurveyInformation inner join Branch on Branch.BranchId = SurveyInformation.BranchId inner join UserInfo on UserInfo.UserId = SurveyInformation.CreatedBy inner join UserInfo u on u.UserId = SurveyInformation.ManagerApproveid where ManagerApprove = 'Approve' or CSRApprove = 'Pending'";
                }

                if (role == "Admin")
                {
                    sql = "select SurveyInformationId,AreaName,userinfo.EmployeeName,BranchName,SurveyDate,ManagerApprove,u.EmployeeName as manager from SurveyInformation inner join Branch on Branch.BranchId = SurveyInformation.BranchId inner join UserInfo on UserInfo.UserId = SurveyInformation.CreatedBy inner join UserInfo u on u.UserId = SurveyInformation.ManagerApproveid where ManagerApprove = 'Approve' or CSRApprove = 'Pending'";
                }

                database db = new database(); db.openconnection();
                SqlCommand cmd = new SqlCommand(sql, db.cn);
                cmd.CommandType = CommandType.Text;
                cmd.Parameters.AddWithValue("@BranchId", Session["BranchId"].ToString());
                //cmd.Parameters.AddWithValue("@UserId", Session["UserId"].ToString());

                SqlDataAdapter da = new SqlDataAdapter(cmd);

                DataTable dt = new DataTable();
                da.Fill(dt);

                db.closeconnection();

                ExportToPDF(dt, "SurveyInformation Report");
            }
            catch
            {
            }
}

私有方法ExportToPDF #

private void ExportToPDF(DataTable dt, string s)
{
            try
            {
                if (dt.Rows.Count > 0)
                {
                    string filename = s + DateTime.Now.ToString(" dd-MM-yyyy hh:mm:ss") + ".pdf";
                    System.IO.StringWriter tw = new System.IO.StringWriter();
                    System.Web.UI.HtmlTextWriter hw = new System.Web.UI.HtmlTextWriter(tw);

                    DataGrid dgGrid = new DataGrid();
                    dgGrid.DataSource = dt;
                    dgGrid.DataBind();

                    //Get the HTML for the control.
                    dgGrid.RenderControl(hw);
                    //Write the HTML back to the browser.
                    Response.ContentType = "application/pdf";
                    Response.AppendHeader("Content-Disposition", "attachment; filename=" + filename + "");
                    //Response.AppendHeader("Content-Disposition", "inline; filename=" + filename + ".pdf");
                    this.EnableViewState = false;
                    Response.Write(tw.ToString());
                    Response.End();
                    Response.Close();
                    Response.Flush();

                    this.Page.ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('Report Export Succesfully')", true);
                }
                else
                {
                    this.Page.ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('No Data to Export')", true);
                }
            }
            catch { }
}

受保护方法btexportblc_Click #

protected void btexportblc_Click(object sender, EventArgs e)
{
    getexportdata();
}

问题根源与修复方案 #

核心问题 #

你当前的代码根本没有生成真正的PDF文件——只是把DataGrid渲染出的HTML文本，强行设置了application/pdf的Content-Type响应头。浏览器收到的是HTML内容，却被标记为PDF格式，自然无法解析加载。

修复步骤 #

1. 替换HTML输出为真实PDF生成逻辑

需要使用专门的PDF生成库（比如iTextSharp、IronPDF）来将数据转换为标准PDF格式。以下是基于iTextSharp（适用于.NET Framework）的修改示例：

首先安装iTextSharp NuGet包，然后改写ExportToPDF方法：

private void ExportToPDF(DataTable dt, string reportTitle)
{
    try
    {
        if (dt.Rows.Count == 0)
        {
            Page.ClientScript.RegisterStartupScript(GetType(), "alert", "alert('No Data to Export')", true);
            return;
        }

        string filename = $"{reportTitle} {DateTime.Now.ToString("dd-MM-yyyy hh:mm:ss")}.pdf";
        using (MemoryStream ms = new MemoryStream())
        {
            // 创建PDF文档实例
            Document document = new Document(PageSize.A4, 25, 25, 30, 30);
            PdfWriter writer = PdfWriter.GetInstance(document, ms);
            document.Open();

            // 添加报表标题
            Paragraph title = new Paragraph(reportTitle, new Font(Font.FontFamily.TIMES_ROMAN, 16, Font.BOLD));
            title.Alignment = Element.ALIGN_CENTER;
            document.Add(title);
            document.Add(new Paragraph("\n"));

            // 创建PDF表格，列数与DataTable一致
            PdfPTable table = new PdfPTable(dt.Columns.Count);
            table.WidthPercentage = 100;

            // 添加表头
            foreach (DataColumn col in dt.Columns)
            {
                PdfPCell cell = new PdfPCell(new Phrase(col.ColumnName, new Font(Font.FontFamily.TIMES_ROMAN, 12, Font.BOLD)));
                cell.BackgroundColor = new BaseColor(240, 240, 240);
                table.AddCell(cell);
            }

            // 添加表格数据行
            foreach (DataRow row in dt.Rows)
            {
                foreach (var item in row.ItemArray)
                {
                    table.AddCell(new Phrase(item.ToString(), new Font(Font.FontFamily.TIMES_ROMAN, 12)));
                }
            }

            document.Add(table);
            document.Close();

            // 将生成的PDF输出到响应流
            Response.Clear();
            Response.ContentType = "application/pdf";
            Response.AppendHeader("Content-Disposition", $"attachment; filename={filename}");
            Response.BinaryWrite(ms.ToArray());
            Response.End();
        }
    }
    catch (Exception ex)
    {
        // 添加异常提示，方便排查问题
        Page.ClientScript.RegisterStartupScript(GetType(), "alert", $"alert('Export failed: {ex.Message}')", true);
    }
}

2. 修复其他潜在问题

• SQL冗余优化：role == "BLC"和role == "Admin"的SQL语句完全一致，可以合并为一个判断，减少冗余代码。
• 异常处理补全：原代码的catch块为空，建议添加日志记录或错误提示，避免问题无法追踪。
• 参数化查询修正：原SQL语句中未使用@BranchId参数，却添加了该参数，会导致SQL执行报错，需在WHERE子句中补充AND Branch.BranchId = @BranchId。
• 响应逻辑修正：原代码中Response.End()之后的Response.Close()、Response.Flush()和脚本注册代码都不会执行，因为Response.End()会直接终止响应流程。

内容的提问来源于stack exchange，提问作者Adnan Attar