<p><strong>Méthode recommandée (EPPlus) :</strong></p>
<pre data-code-wrap="csharp"><code class="lang-csharp">using OfficeOpenXml;
using (var package = new ExcelPackage(new FileInfo("fichier.xlsx")))
{
var ws = package.Workbook.Worksheets[0];
string val = ws.Cells[1, 1].Value?.ToString();
}
</code></pre>
<p><strong>Avec Interop (nécessite Excel installé) :</strong></p>
<pre data-code-wrap="csharp"><code class="lang-csharp">var excelApp = new Microsoft.Office.Interop.Excel.Application();
var workbook = excelApp.Workbooks.Open(@"C:\fichier.xlsx");
</code></pre>