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Editorial Team
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Asked: 2026-05-11T19:41:52+00:00

I’m adding a function to my own personal toolkit lib to do simple CSV

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I’m adding a function to my own personal toolkit lib to do simple CSV to HTML table conversion.

I would like the smallest possible piece of code to do this in C#, and it needs to be able to handle CSV files in excess of ~500mb.

So far my two contenders are

  • splitting csv into arrays by
    delimiters and building HTML output

  • search-replace delimiters with table
    th tr td tags

Assume that the file/read/disk operations are already handled… i.e., i’m passing a string containing the contents of said CSV into this function. The output will consist of straight up simple HTML style-free markup, and yes the data may have stray commas and breaks therein.

update: some folks asked. 100% of the CSV i deal with comes straight out of excel if that helps.

Example string:

a1,b1,c1\r\n
a2,b2,c2\r\n
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1 Answer

  1. Editorial Team

    Read All Lines into Memory

        var lines =File.ReadAllLines(args[0]);
    using (var outfs = File.AppendText(args[1]))
    {
        outfs.Write("<html><body><table>");
        foreach (var line in lines)
            outfs.Write("<tr><td>" + string.Join("</td><td>", line.Split(',')) + "</td></tr>");
        outfs.Write("</table></body></html>");
    }

    or Read one line at a time

        using (var inFs = File.OpenText(args[0]))
    using (var outfs = File.AppendText(args[1]))
    {
        outfs.Write("<html><body><table>");
        while (!inFs.EndOfStream )
            outfs.Write("<tr><td>" + string.Join("</td><td>", inFs.ReadLine().Split(',')) + "</td></tr>");
        outfs.Write("</table></body></html>");
    }

    … @Jimmy … I created an extended version using LINQ. Here is the highlight … (lazy eval for line reading)

        using (var lp = args[0].Load())
        lp.Select(l => "<tr><td>" + string.Join("</td><td>", l.Split(',')) + "</td></tr>")
        .Write("<html><body><table>", "</table></body></html>", args[1]);
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