OpenXML - How can I insert a value into a specific worksheet?

Question

I'm fairly new to creating Excel spreadsheets in C# and I'm looking for advice. I've spent 2 or 3 days now looking through documentation and blogs etc but I cannot seem to find an answer to a common task.

I need to insert a text value into a specific worksheet. I cant easily post my code at the moment but it appears to be an issue with every example I've seen of the definition of a sheet, it always gets the first child.

I need to iterate through all sheets and dependant on the sheet name then go and insert a value.

I.e. If the sheet name = "testA" then write TestA, if the sheet name = "testB" then write "TestB".

Currently I can insert a value for the workbook but it inserts the same value for every sheet.

Sheets sheets = workbookPart.Workbook.GetFirstChild<Sheets>();

[Microsoft documentation] (https://learn.microsoft.com/en-us/office/open-xml/how-to-insert-text-into-a-cell-in-a-spreadsheet)

Please note I'm not just giving up on this I've just reached a bit of a wall with it and need some pointers.

Many Thanks, J

Namespaces I'm using:

using DocumentFormat.OpenXml;
using DocumentFormat.OpenXml.Packaging;
using DocumentFormat.OpenXml.Spreadsheet;


private void btnExport_Click(object sender, EventArgs e)
    {

        //Using Microsofts Interop class to create Excel files gives mixed resuts and requires excel to be installed.
        // This uses OpenXML library to achieve this and doesnt require excel to be installed: https://medium.com/swlh/openxml-sdk-brief-guide-c-7099e2391059


        string filepath = "Test.xlsx";
        // Create a spreadsheet document by supplying the filepath.
        // By default, AutoSave = true, Editable = true, and Type = xlsx.
        SpreadsheetDocument spreadsheetDocument = SpreadsheetDocument.
            Create(filepath, SpreadsheetDocumentType.Workbook);

        // Add a WorkbookPart to the document.
        WorkbookPart workbookpart = spreadsheetDocument.AddWorkbookPart();
        workbookpart.Workbook = new Workbook();

        // Add a WorksheetPart to the WorkbookPart.
        WorksheetPart worksheetPart = workbookpart.AddNewPart<WorksheetPart>();
        worksheetPart.Worksheet = new Worksheet(new SheetData());

        // Add Sheets to the Workbook.
        Sheets sheets = spreadsheetDocument.WorkbookPart.Workbook.
            AppendChild<Sheets>(new Sheets());

        // Append a new worksheet and associate it with the workbook.
        Sheet sheetOne = new Sheet()
        {
            Id = spreadsheetDocument.WorkbookPart.
            GetIdOfPart(worksheetPart),
            SheetId = 1,
            Name = "Sheet1"
        };

        Sheet sheetTwo= new Sheet()
        {
            Id = spreadsheetDocument.WorkbookPart.
            GetIdOfPart(worksheetPart),
            SheetId = 2,
            Name = "Sheet2"
        };

        Sheet sheetParameters = new Sheet()
        {
            Id = spreadsheetDocument.WorkbookPart.
            GetIdOfPart(worksheetPart),
            SheetId = 3,
            Name = "Parameters"
        };

        Sheet sheetFour= new Sheet()
        {
            Id = spreadsheetDocument.WorkbookPart.
            GetIdOfPart(worksheetPart),
            SheetId = 4,
            Name = "Sheet4"
        };

        Sheet sheetFive= new Sheet()
        {
            Id = spreadsheetDocument.WorkbookPart.
            GetIdOfPart(worksheetPart),
            SheetId = 5,
            Name = "Sheet5"
        };

        

        sheets.Append(sheetOne);
        sheets.Append(sheetTwo);
        sheets.Append(sheetParameters);
        sheets.Append(sheetFour);
        sheets.Append(sheetFive);

        
        
        workbookpart.Workbook.Save();
        // Close the document.

        
        spreadsheetDocument.Close();

        //InsertTextExistingExcel(filepath, "test1", "A", 1, "Parameters");
        InsertInSheet(filepath, "test1", "A", 1, "Parameters");
        //Any of these lists empty?

       


    }

    public static void InsertInSheet(string filePath, string value, string columnName, uint rowIndex, string sheetName)
    {
        using (SpreadsheetDocument spreadSheet = SpreadsheetDocument.Open(filePath, true))
        {
            getSheetDetails(spreadSheet);
        }
    }



  

    //work here
    public static void getSheetDetails(SpreadsheetDocument doc)
    {
        WorksheetPart worksheetPart;
        //iterate through sheets
        foreach (Sheet sheetDetail in doc.WorkbookPart.Workbook.Sheets)
        {
            if (sheetDetail.Name == "Parameters")
            {
                //each sheet has a worksheetPart
                worksheetPart = (WorksheetPart)doc.WorkbookPart.GetPartById(sheetDetail.Id);
                Cell cell = InsertCellInWorksheet("A", 1, worksheetPart);

                
                cell.CellValue = new CellValue("test");
                cell.DataType = new EnumValue<CellValues>(CellValues.String);

                worksheetPart.Worksheet.Save();


            }
            

        }
    }






    private static Cell InsertCellInWorksheet(string columnName, uint rowIndex, WorksheetPart worksheetPart)
    {
        //fix earlier worksheetPart only has a count of 1
        Worksheet worksheet = worksheetPart.Worksheet;
        //fix this to point to sheet
        //SheetData sheetData = worksheet.Descendants<SheetData>();
        SheetData sheetData = worksheet.GetFirstChild<SheetData>();

        MessageBox.Show(sheetData.InnerXml.ToString());




        string cellReference = columnName + rowIndex;

        Row row;
        if (sheetData.Elements<Row>().Where(r => r.RowIndex == rowIndex).Count() != 0)
        {
            row = sheetData.Elements<Row>().Where(r => r.RowIndex == rowIndex).First();
        }
        else
        {
            row = new Row() { RowIndex = rowIndex };
            sheetData.Append(row);
        }

        Cell refCell = row.Descendants<Cell>().LastOrDefault();

        Cell newCell = new Cell() { CellReference = cellReference };
        row.InsertAfter(newCell, refCell);

        worksheet.Save();
        return newCell;

    }