Bulk excel import

[Mike6x]

Please demo Bulk excel import function whith gerenic method . I try as following but processsing is slow:

public class ExcelReader : IExcelReader
{
public async Task<IList> ImportAsync(FileUploadRequest request, FileType supportedFileType, string sheetName = "Sheet1")
{

    string base64Data = Regex.Match(request.Data, string.Format("data:{0}/(?<type>.+?),(?<data>.+)", supportedFileType.ToString().ToLower())).Groups["data"].Value;
    var streamData = new MemoryStream(Convert.FromBase64String(base64Data));

    List<T> list = new List<T>();
    Type typeOfObject = typeof(T);
    using (IXLWorkbook workbook = new XLWorkbook(streamData))
    {
        // Read the first Sheet from Excel file.
        var worksheet = workbook.Worksheets.FirstOrDefault(w => w.Name == sheetName);
        if (worksheet != null)
        {
            var properties = typeOfObject.GetProperties();

            // header column texts
            var columns = worksheet.FirstRow().Cells().Select((v, i) => new { v.Value, Index = i + 1 });

            // indexing in closedxml starts with 1 not from 0
            // Skip first row which is used for column header texts
            foreach (IXLRow row in worksheet.RowsUsed().Skip(1))
            {
                T item = (T)Activator.CreateInstance(typeOfObject);
                foreach (var prop in properties)
                {
                    try
                    {
                        var type = prop.PropertyType;
                        int colIndex = columns.Single(c => c.Value.ToString() == prop.Name).Index;

                        object? obj = GetObjectByDataType(type, row.Cell(colIndex).Value);
                        prop.SetValue(item, obj);
                    }
                    catch
                    {
                    }
                }
                if (item != null) list.Add(item);
            }
        }
    }

    return await Task.FromResult(list);
}

private static object? GetObjectByDataType(Type propertyType, XLCellValue cellValue)
{
    if (cellValue.ToString() == "null" )
    {
        return null;
    }

    object? val;

    if (propertyType.IsEnum)
    {
        val = Convert.ToInt32(cellValue.GetNumber());
        return Enum.ToObject(propertyType, val);
    }
    else if (propertyType == typeof(Guid) || propertyType == typeof(Guid?))
    {
        val = Guid.Parse(cellValue.ToString());
    }
    else if (propertyType == typeof(int) || propertyType == typeof(int?))
    {
        val = Convert.ToInt32(cellValue.GetNumber());
    }
    else if (propertyType == typeof(decimal))
    {
        val = Convert.ToDecimal(cellValue.GetNumber());
    }
    else if (propertyType == typeof(long))
    {
        val = Convert.ToInt64(cellValue.GetNumber());
    }
    else if (propertyType == typeof(bool) || propertyType == typeof(bool?))
    {
        val = Convert.ToBoolean(cellValue.GetBoolean());
    }
    else if (propertyType == typeof(DateTime) || propertyType == typeof(DateTime?))
    {
        val = Convert.ToDateTime(cellValue.GetDateTime());
    }
    else
    {
        val = cellValue.ToString();
    }
    return Convert.ChangeType(val, Nullable.GetUnderlyingType(propertyType) ?? propertyType);
}

}