在C#中，可以使用OpenXml库来比较和编辑Excel行。下面是一个使用OpenXml库的代码示例：

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

public class ExcelEditor
{
    public void CompareAndEditExcelRow(string filePath, int rowNumber, string newValue)
    {
        using (SpreadsheetDocument document = SpreadsheetDocument.Open(filePath, true))
        {
            WorkbookPart workbookPart = document.WorkbookPart;
            WorksheetPart worksheetPart = workbookPart.WorksheetParts.First();
            SheetData sheetData = worksheetPart.Worksheet.Elements().First();
            Row row = sheetData.Elements().FirstOrDefault(r => r.RowIndex == rowNumber);
            
            if (row != null)
            {
                foreach (Cell cell in row.Elements())
                {
                    string cellValue = GetCellValue(cell, workbookPart);
                    if (cellValue == newValue)
                    {
                        // Do something if the cell value matches the new value
                    }
                    else
                    {
                        // Update the cell value to the new value
                        UpdateCellValue(cell, workbookPart, newValue);
                    }
                }
            }
        }
    }

    private string GetCellValue(Cell cell, WorkbookPart workbookPart)
    {
        string cellValue = string.Empty;
        if (cell.DataType != null && cell.DataType.Value == CellValues.SharedString)
        {
            SharedStringTablePart sharedStringPart = workbookPart.GetPartsOfType().FirstOrDefault();
            if (sharedStringPart != null)
            {
                cellValue = sharedStringPart.SharedStringTable.ElementAt(int.Parse(cell.CellValue.Text)).InnerText;
            }
        }
        else
        {
            cellValue = cell.CellValue.Text;
        }
        return cellValue;
    }

    private void UpdateCellValue(Cell cell, WorkbookPart workbookPart, string newValue)
    {
        cell.DataType = new EnumValue(CellValues.SharedString);
        SharedStringTablePart sharedStringPart = workbookPart.GetPartsOfType().FirstOrDefault();
        if (sharedStringPart == null)
        {
            sharedStringPart = workbookPart.AddNewPart();
        }
        int index = InsertSharedStringItem(newValue, sharedStringPart);
        cell.CellValue = new CellValue(index.ToString());
        workbookPart.Workbook.Save();
    }

    private int InsertSharedStringItem(string text, SharedStringTablePart sharedStringPart)
    {
        if (sharedStringPart.SharedStringTable == null)
        {
            sharedStringPart.SharedStringTable = new SharedStringTable();
        }
        int index = 0;
        foreach (SharedStringItem item in sharedStringPart.SharedStringTable.Elements())
        {
            if (item.InnerText == text)
            {
                return index;
            }
            index++;
        }
        sharedStringPart.SharedStringTable.AppendChild(new SharedStringItem(new Text(text)));
        sharedStringPart.SharedStringTable.Save();
        return index;
    }
}

使用上述代码可以打开一个Excel文件，找到指定行号的行，并比较每个单元格的值。如果单元格的值与新值相同，则可以执行某些操作。否则，将单元格的值更新为新值。请注意，上述代码假定Excel文件中的单元格值是字符串类型。如果单元格包含其他类型的值，请根据需要进行调整。

为了使用上述代码，你需要在项目中安装OpenXml库。可以通过NuGet包管理器来安装OpenXml库。