Convert HTML ↔ XLSX | MHTML ↔ Spreadsheet in .NET – Supercharge Your Data‑Flow with Sheet & Size

using Sheetize;

// 1️⃣ Register your license
Sheetize.License license = new Sheetize.License();
license.SetLicense(@"C:\Licenses\Sheetize.HtmlConverter_for_.NET.lic");

// 2️⃣ Load the source HTML (or MHTML) file
var loadOptions = new LoadOptions
{
InputFile = @"C:\Docs\SalesReport.html"
};

// 3️⃣ Choose the target spreadsheet format
var saveOptions = new HtmlSaveOptions
{
OutputFile = @"C:\Exports\SalesReport.xlsx",
SaveFormat = FileFormatType.Xlsx // pick Xlsb, Csv, Xml, Tsv, etc.
};

// 4️⃣ Run the conversion
HtmlConverter.Process(loadOptions, saveOptions);

using Sheetize;

// Register the license
Sheetize.License license = new Sheetize.License();
license.SetLicense(@"C:\Licenses\Sheetize.HtmlConverter_for_.NET.lic");

// Load the spreadsheet file
var loadOptions = new LoadOptions
{
InputFile = @"C:\Docs\ProjectBudget.xlsx"
};

// Export to HTML (or MHTML)
var saveOptions = new HtmlSaveOptions
{
OutputFile = @"C:\Exports\ProjectBudget.html",
SaveFormat = FileFormatType.Html // or FileFormatType.MHtml
};

HtmlConverter.Process(loadOptions, saveOptions);

using Sheetize; // same namespace for HTML‑Spreadsheet converter
using System.IO;

try
{
// 1️⃣ License validation
var license = new Sheetize.License();
license.SetLicense(@"C:\Licenses\Sheetize.HtmlConverter_for_.NET.lic");

// 2️⃣ Input verification – must be .html or .mhtml, or any spreadsheet type
string inputPath = @"C:\Docs\Report.mhtml";
if (!File.Exists(inputPath))
throw new FileNotFoundException($"Input file not found: {inputPath}");

var htmlExts = new[] { ".html", ".htm", ".mhtml", ".mht" };
var spreadsheetExts = new[]
{
".xlsx", ".xlsb", ".xlsm", ".xltm", ".xlam",
".xls", ".xlw", ".xlt", ".csv", ".tsv",
".sqlscript", ".dif", ".xml"
};
string inputExt = Path.GetExtension(inputPath).ToLower();
if (!htmlExts.Contains(inputExt) && !spreadsheetExts.Contains(inputExt))
throw new NotSupportedException("Unsupported input file type.");

// 3️⃣ Output verification – must contain the opposite family
string outputPath = @"C:\Exports\Report.xlsx";
string outputExt = Path.GetExtension(outputPath).ToLower();
if (!htmlExts.Contains(outputExt) && !spreadsheetExts.Contains(outputExt))
throw new NotSupportedException("Unsupported output file type.");

// Ensure we have at least one HTML/MHTML side
if (!htmlExts.Contains(inputExt) && !htmlExts.Contains(outputExt))
throw new InvalidOperationException("At least one side of the conversion must be HTML or MHTML.");

// 4️⃣ Build conversion options
var loadOptions = new LoadOptions { InputFile = inputPath };
var saveOptions = new HtmlSaveOptions
{
OutputFile = outputPath,
SaveFormat = outputExt switch
{
".html" => FileFormatType.Html,
".mhtml" => FileFormatType.MHtml,
".xlsx" => FileFormatType.Xlsx,
".xlsb" => FileFormatType.Xlsb,
".xlsm" => FileFormatType.Xlsm,
".csv" => FileFormatType.Csv,
".tsv" => FileFormatType.Tsv,
".xml" => FileFormatType.Xml,
".sqlscript" => FileFormatType.SqlScript,
".dif" => FileFormatType.Dif,
_ => throw new NotSupportedException("Unknown output format.")
}
};

// 5️⃣ Execute conversion
HtmlConverter.Process(loadOptions, saveOptions);
Console.WriteLine($"✅ Conversion succeeded: {outputPath}");
}
catch (Exception ex)
{
// Centralised logging – replace with Serilog, NLog, etc. as needed
Console.Error.WriteLine($"❌ Conversion failed: {ex.GetType().Name} – {ex.Message}");
// Optionally re‑throw for upstream handling
// throw;
}

# 1️⃣ Add the NuGet package
dotnet add package Sheetize

# 2️⃣ Grab a free trial license (no credit‑card required)
# https://purchase.sheetize.com/temp-license/113911

# 3️⃣ Drop the *.lic file into your project folder and reference it as shown above.

# 4️⃣ Run one of the code snippets – compile and watch the conversion happen!