how to hide a row in excel using open xml?

If you don't mind using other solutions, you can check the following example using Free Spire.XLS (https://www.e-iceblue.com/Download/download-excel-for-net-free.html)

using Spire.Xls;

namespace HideExcelRows
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a Workbook instance
            Workbook workbook = new Workbook();
            //Load an Excel file
            workbook.LoadFromFile("Input.xlsx");

            //Get the first worksheet
            Worksheet sheet = workbook.Worksheets[0];

            //Hide the 3rd row
            sheet.HideRow(3);

            //Save the result file
            workbook.SaveToFile("HideRows.xlsx", ExcelVersion.Version2013);
        }
    }
}

Hi,

First open the file for updating by passing true as the second parameter of SpreadsheetDocument.Open method. Second, after changing the Hidden property on row, save the workSheet.

	const string fileName = @"C:\Users\ljoseph\Documents\Book1.xlsx";


	using (SpreadsheetDocument document = SpreadsheetDocument.Open(fileName, true))
	{
		WorkbookPart wbPart = document.WorkbookPart;
		var sheets = wbPart.Workbook.Descendants();
		var sheet = sheets.First();


		var workSheet = ((WorksheetPart)wbPart.GetPartById(sheet.Id)).Worksheet;
		var sheetData = workSheet.Elements().First();
		var row = sheetData.Elements().Where(r => r.RowIndex.Value == 2).First();
		row.Hidden = true;
		workSheet.Save();
	}