如何使用FastReport Core以PDF格式下載報表

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本文將展示如何創(chuàng)建一個按鈕，實現一鍵將報表從瀏覽器下載到本地。我們將在最終文件的功能中使用導出為PDF（當然你可以使用任何其他格式）。

首先，創(chuàng)建一個ASP.NET Core Web Application項目并添加下列庫：FastReport Core、Microsoft.EntitiyFrameworkCore.Sqlite以及Microsoft.EntitiyFrameworkCore.Sqlite.Design。這樣，你就有了已安裝好的以下軟件包：

讓我們預先處理數據。我們需要SQLite數據庫 - fastreport.db。可以從示范項目“C:\ Program Files (x86)\FastReports\FastReport.Net\Demos\Core\FastReportCore.MVC” 中獲取。將數據庫直接添加到項目的根目錄。另外，我們從項目文件夾“C:\Program Files (x86)\FastReports\FastReport.Net\Demos\Reports”中添加報告模板“Simple List.frx”。

現在，在Models文件夾中，添加一個新的類。我們稱之為ApplicationDbContext.cs。從名字你大概就能看出來了 - 這是數據的上下文。這是它的內容：

using Microsoft.EntityFrameworkCore;
using System;
using System.Data;
using System.Reflection;
 
namespace FRCore
{
 public class ApplicationDbContext : DbContext
 {
 public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
 : base(options)
 { }
 
 public ApplicationDbContext()
 {
 
 }
 
 public DbSet<Employees> Employees { get; set; }
 
 // Get the data set
 public DataSet GetDataSet(string name)
 {
 DataSet set = new DataSet(name);
 set.Tables.Add(GetTable(Employees, "Employees"));
 return set;
 }
 
 // Set the primary key
 protected override void OnModelCreating(ModelBuilder modelBuilder)
 {
 modelBuilder.Entity<Employees>(entity =>
 {
 entity.HasKey(e => e.EmployeeId)
 .HasName("sqlite_autoindex_employees_1");
 });
 }
 
 // Set the data source
 protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
 {
#warning To protect potentially sensitive information in your connection string, you should move it out of source code. See //go.microsoft.com/fwlink/?LinkId=723263 for guidance on storing connection strings.
 optionsBuilder.UseSqlite(@"data source= fastreport.db");
 }
 
 // Get the table you need to create a report. In fact, the method of converting IQuerable into a DataTable
 static DataTable GetTable<TEntity>(DbSet<TEntity> table, string name) where TEntity : class
 {
 DataTable result = new DataTable(name);
 PropertyInfo[] infos = typeof(TEntity).GetProperties();
 foreach (PropertyInfo info in infos)
 {
 if (info.PropertyType.IsGenericType
 && info.PropertyType.GetGenericTypeDefinition() == typeof(Nullable<>))
 result.Columns.Add(new DataColumn(info.Name, Nullable.GetUnderlyingType(info.PropertyType)));
 else
 result.Columns.Add(new DataColumn(info.Name, info.PropertyType));
 }
 foreach (var el in table)
 {
 DataRow row = result.NewRow();
 foreach (PropertyInfo info in infos)
 if (info.PropertyType.IsGenericType
 && info.PropertyType.GetGenericTypeDefinition() == typeof(Nullable<>))
 {
 object t = info.GetValue(el);
 if (t == null)
 t = Activator.CreateInstance(Nullable.GetUnderlyingType(info.PropertyType));
 row[info.Name] = t;
 }
 else
 row[info.Name] = info.GetValue(el);
 result.Rows.Add(row);
 }
 return result;
 }
 }
 
 // The Employees table model
 public class Employees
 {
 public int EmployeeID { get; set; }
 public int EmployeeId { get; set; }
 public string LastName { get; set; }
 public string FirstName { get; set; }
 public string Title { get; set; }
 public string TitleOfCourtesy { get; set; }
 public System.DateTime? BirthDate { get; set; }
 public System.DateTime? HireDate { get; set; }
 public string Address { get; set; }
 public string City { get; set; }
 public string Region { get; set; }
 public string PostalCode { get; set; }
 public string Country { get; set; }
 public string HomePhone { get; set; }
 public string Extension { get; set; }
 public byte[] Photo { get; set; }
 public string Notes { get; set; }
 public int? ReportsTo { get; set; }
 }
}

在這個類中（在連接到數據庫后）我們得到一組數據并將其轉換為一個DataTable，這是FastReport生成報表所需的。將在報表中使用的Employees表的模型由一個單獨的類表示。

現在我們開始編輯HomeController.cs。 

using System.Diagnostics;
using Microsoft.AspNetCore.Mvc;
using FRCore.Models;
using FastReport;
using FastReport.Export.Html;
using System.IO;
using System.Text;
using FastReport.Export.Pdf;
using System.Data;
 
namespace FRCore.Controllers
{
 public class HomeController : Controller
 {
 public Report report = new Report();
 
 private ApplicationDbContext _context = new ApplicationDbContext();
 
 public ApplicationDbContext GetContext()
 {
 return _context;
 }
 
 public IActionResult Index()
 {
 DataSet dataSet = new DataSet();
 dataSet = GetContext().GetDataSet("NorthWind");
 report.Report.RegisterData(dataSet, "NorthWind");
 report.Report.Load("Simple List.frx");
 report.Prepare();
 
 HTMLExport export = new HTMLExport();
 export.Layers = true;
 using (MemoryStream ms = new MemoryStream())
 {
 export.EmbedPictures = true;
 export.Export(report, ms);
 ms.Flush();
 ViewData["Report"] = Encoding.UTF8.GetString(ms.ToArray());
 ViewData["ReportName"] = "Simple List.frx";
 }
 return View();
 }
 
 public IActionResult Pdf()
 {
 System.Data.DataSet dataSet = new System.Data.DataSet();
 dataSet = GetContext().GetDataSet("NorthWind");
 report.Report.RegisterData(dataSet, "NorthWind");
 report.Report.Load("Simple List.frx");
 report.Prepare();
 
 PDFExport export = new PDFExport();
 using (MemoryStream ms = new MemoryStream())
 {
 export.Export(report, ms);
 ms.Flush();
 return File(ms.ToArray(), "application/pdf", Path.GetFileNameWithoutExtension("Simple List") + ".pdf");
 }
 }
 }
}

Index方法只是以html格式顯示報表，而PDF方法則生成一個用于下載的PDF文件。這兩種方法都使用報表的數據上下文。

現在改變Index.cshtml的顯示形式：

@{
 ViewData["Title"] = "Home Page";
}
@if (ViewData.ContainsKey("ReportName"))
{
 <a class="btn btn-danger" asp-controller="Home" asp-action="Pdf" asp-route-report="@ViewData["ReportName"]">Download PDF</a>
}
@if (ViewData.ContainsKey("Report"))
{
 @Html.Raw(ViewData["Report"])
}

我們首先添加了一個PDF下載按鈕，然后顯示報表。

運行應用程序：

我們按下“下載PDF”按鈕，并以PDF格式下載報表文件。總而言之，實現起來相當簡單。

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