在大型数据集上拆分PDF文件-为每一定数量的行/页创建多个PDF文件C＃

Question

I have a large dataset of 89k rows that I need to export to a PDF file. With my current code I can export 30k rows perfectly fine, but when I increase the .Take to be more than 30k I get "Document has no pages" error. Now what I am trying to achieve is to create a PDF document for every 30k rows in the dataset such that

from this 89k rows..
file a -> 30k rows
file b -> 30k rows
file c -> 29k rows

ie as long as theres rows/records split the file creation to every 30k rows you get. This is my current code

var list = conStrings.GetReport().Take(30000); //get rows from DB/table

WebGrid grid = new WebGrid(source: list, canPage: false, canSort: false);            
        string gridHtml = grid.GetHtml(
                                        tableStyle: "webgrid-table",
                                        headerStyle: "webgrid-header",                                            
            columns: grid.Columns(
                    grid.Column("q_barcode", "Barcode"),
                    grid.Column("q_description", "Description"),
                    grid.Column("q_sellprice","Price", format: (item) => new HtmlString("€" + Convert.ToString(item.q_sellprice))),
                    grid.Column("unitCost","Unit Cost", format: (item) => new HtmlString("€" + Convert.ToString(item.unitCost))),
                    grid.Column("VatRate","Vat Rate %", format: (item) => new HtmlString(Convert.ToString(item.VatRate + "%"))),
                    grid.Column("grossProfit","GP %", format: (item) => new HtmlString(Convert.ToString(item.grossProfit + "%")))
                )
            ).ToString();


using (var ms = new MemoryStream())
{
//iTextSharp Document which is an abstraction of a PDF but **NOT * *a PDF
using (var doc = new Document())
{
    //writer that's bound to our PDF abstraction and our stream  
    using (var writer = PdfWriter.GetInstance(doc, ms))
    {
        // open the document for writing
        doc.Open();

        // read html data to StringReader 
        //using (var srHtml = new StringReader(gridHtml))
        using (var msCss = new MemoryStream(Encoding.UTF8.GetBytes(webgridstyle)))
        {
            using (var srHtml = new MemoryStream(Encoding.UTF8.GetBytes(gridHtml)))
            {
                iTextSharp.tool.xml.XMLWorkerHelper.GetInstance()
                    .ParseXHtml(writer, doc, srHtml, msCss);
            }
        }

        doc.Close();
    }
}

  myBytes = ms.ToArray();
}

var testFile = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "PDF_Report_"+timestamp+".pdf");

System.IO.File.WriteAllBytes(testFile, myBytes);

So from this code I would like to be able to just say

var list = conStrings.GetReport(); //get data from DB regardless of size

and create a document every 30k rows/or 500 pages (eg). Whats the best way to achieve this?

Answer 1

You can run the ParseXhtml method multiple times on the same iText document with different HTML snippets.

I'm not familiar with WebGrid, but I assume you should be able to call Take() multiple times and store the results in a List. Then later you can loop over this list of HTML snippets and then call ParseXhtml() per HTML snippet.

This will lead to tables not filling the pages when they hit the end of the paginated result. You can also merge the HTML snippets using XML parsing.

Answer 2

try it like this:

var batchedList = conStrings.GetReport()
.Select((data,index) => new {data, index})
.GroupBy(item => item.index / 30000)
.Select(grp => grp.Select(x => x.data));

foreach(var list in batchedList)
{
    {{INSERT RESET OF YOUR METHOD HERE}}
}

This should batch the results of "conStrings.GetReport()" into groups of 30k and then foreach over the results

Obviously this line:

var list = conStrings.GetReport().Take(30000); //get rows from DB/table

wont be needed inside the foreach loop.