c# - 如何导出到 Excel？

Question

我关注了this guide这是在另一篇关于此的帖子中推荐的，但我不能完全让它工作。尝试重定向到/LogModelsController/ExportData 时出现 404 错误，据我所知，这是我应该做的。

_LogPartialLayout.cshtml

@using (Html.BeginForm("ExportData", "LogModelsController", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
    <table class="table">
        <tr>
            <th>
                @Html.ActionLink("message", "Index", new { sortOrder = ViewBag.NameSortParm, currentFilter = ViewBag.CurrentFilter })

            </th>
            <th>
                @Html.ActionLink("timestamp", "Index", new { sortOrder = ViewBag.NameSortParm, currentFilter = ViewBag.CurrentFilter })
            </th>
            <th>
                @Html.ActionLink("level", "Index", new { sortOrder = ViewBag.NameSortParm, currentFilter = ViewBag.CurrentFilter })
            </th>

        </tr>

        @foreach (var item in Model)
        {
            <tr>
                <td>
                    @Html.DisplayFor(modelItem => item.message)
                </td>
                <td>
                    @Html.DisplayFor(modelItem => item.timeStamp)
                </td>
                <td>
                    @Html.DisplayFor(modelItem => item.level)
                </td>
            </tr>
        }
    </table>
    <input type="submit" name="Export" id="Export" value="Export" />
}

LogModelsController.cs

public ActionResult ExportData()
        {
            GridView gv = new GridView();
            gv.DataSource = db.Log.ToList();
            gv.DataBind();
            Response.ClearContent();
            Response.Buffer = true;
            Response.AddHeader("content-disposition", "attachment; filename=Loglist.xls");
            Response.ContentType = "application/ms-excel";
            Response.Charset = "";
            StringWriter sw = new StringWriter();
            HtmlTextWriter htw = new HtmlTextWriter(sw);
            gv.RenderControl(htw);
            Response.Output.Write(sw.ToString());
            Response.Flush();
            Response.End();

            return RedirectToAction("~/LogModels/Index");
        }

LogModel.cs

namespace ASDMVC.Models
{
    [Table("Log")]
    public class LogModel
    {
        [Key]
        public long id { get; set; }
        public string message { get; set; }
        public DateTime timeStamp { get; set; }
        public string level { get; set; }
        public int customerId { get; set; }
    }

    public class LogDBContext:DbContext
    {
        public LogDBContext() : base("MySqlConnection")
        {

        }

        public DbSet <LogModel> Log { get; set; }

    }
}

TD;DR:如何将此表正确导出到 Excel？

奖励:它也适用于 PagedList 吗？

---

编辑 3 - 已解决

Index.cshtml:

@using (Html.BeginForm("ExportData", "LogModels"))
{
    <input type="submit" name="Export" id="Export" value="Export" />
}

LogModelsController.cs

public ActionResult ExportData()
{
    DataTable dataTable = GetData();

    using (ExcelPackage package = new ExcelPackage())
    {
        var ws = package.Workbook.Worksheets.Add("My Sheet");
        //true generates headers
        ws.Cells["A1"].LoadFromDataTable(dataTable, true);

        var stream = new MemoryStream();
        package.SaveAs(stream);

        string fileName = "myfilename.xlsx";
        string contentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";

        stream.Position = 0;
        return File(stream, contentType, fileName);
    }
}

public DataTable GetData()
{
    DataTable dt = new DataTable();
    if (ModelState.IsValid)
    {
        using (SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["MySqlConnection"].ConnectionString))
        {
            using (SqlCommand comm = conn.CreateCommand())
            {
                comm.Parameters.AddWithValue("@val1", Session["myID"]);
                comm.CommandText = "SELECT * FROM dbo.Log WHERE CustomerId = @val1";
                try
                {
                    conn.Open();
                    dt.Load(comm.ExecuteReader());
                }
                catch (SqlException e)
                {
                    throw new Exception(e.ToString());
                }
            }
        }
    }
    return dt;
}

我在 CommandText 中犯了一个错误，用“Id”代替了“CustomerId”——它现在返回 Excel 文件中的整个表格。

Answer 1

该指南没有展示如何创建 Excel 文件，它展示了创建带有表格的 HTML 文件的技巧。 Excel 将尝试使用默认设置导入带有表格的 csv 或 HTML 文件，这通常会失败。

使用 EPPlus 这样的库创建正确 Excel 文件要容易得多.我确定之前已经回答过这个问题，但我找不到同时显示如何 create an Excel file from data 的答案。并设置 proper content type对于 xlsx 文件。

EPPlus 提供 LoadFromDataTable 和 LoadFromCollection 方法，用从 DataTable 或通用集合中提取的数据填充 Excel 范围。列名或属性名分别用作标题。

public ActionResult ExportData()
{

    //Somehow, load data to a DataTable

    using (ExcelPackage package = new ExcelPackage())
    {
        var ws = package.Workbook.Worksheets.Add("My Sheet");
        //true generates headers
        ws.Cells["A1"].LoadFromDataTable(dataTable, true);

        var stream = new MemoryStream();
        package.SaveAs(stream);

        string fileName = "myfilename.xlsx";
        string contentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";

        stream.Position = 0;
        return File(stream, contentType, fileName);
    }
}

LoadFromDataTable 或 LoadFromCollection 返回可用于格式化表格的 Excel 单元格范围:

var range=ws.Cells["A1"].LoadFromDataTable(table);
range.Style.Numberformat.Format = "#,##0.00";
range.Style.HorizontalAlignment = ExcelHorizontalAlignment.Right;

您还可以将表格样式应用于范围，或将所需样式传递给 LoadFromDataTable 或 LoadFromCollection，例如:

ws.Cells[1,1].LoadFromDataTable(table, true, TableStyles.Light1);

图书馆的Githup wiki显示如何 format the result 、生成公式、数据透视表、处理表格等。

如果您想创建一个相对较大的工作表，保存到 MemoryStream 可能是个问题。将相同的数据写入两次，一次写入 MemoryStream，然后将其复制到输出，这会浪费周期。但是，直接从 MVC 操作写入输出流是一种不好的做法。诀窍是创建一个自定义 FileResult 来处理 EPPlus 包并返回它而不是 File 返回的 FileResult，例如:

public class EpplusResult:FileResult
{
    public EpplusResult(ExcelPackage package)
        : base("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
    {
        if (package == null)
        {
            throw new ArgumentNullException("package");
        }

        Package = package;
    }

    public ExcelPackage Package { get; private set; }

    protected override void WriteFile(HttpResponseBase response)
    {
        // grab chunks of data and write to the output stream
        Stream outputStream = response.OutputStream;
        using (Package)
        {
            Package.SaveAs(outputStream);
        }
    }
}

它允许您编写以下操作:

public FileResult ExportData()
{

    ExcelPackage package = new ExcelPackage();
    var ws = package.Workbook.Worksheets.Add("My Sheet");       
    ...
    ws.Cells[1,1].LoadFromDataTable(table, true, TableStyles.Light1);

    return new EpplusResult(package){FileDownloadName = "SomeFile.xlsx"};
}