Helpers for easily mapping objects to rows of an excel document in c# using EPPlus library

ExcelWritingHelpers.cs

private static ExcelRangeBase GetColumnByName(ExcelWorksheet sheet, string columnName)
{
    return sheet.Cells["1:1"].FirstOrDefault(x => x.Value.ToString() == columnName);
}

private static void MapColumns<TExportObject>(int row, ExcelWorksheet sheet, List<string> columnNames, List<Expression<Func<TExportObject, object>>> maps, TExportObject source)
{
    for (var i = 0; i < columnNames.Count; i++)
    {
        var columnName = columnNames[i];
        var column = GetColumnByName(sheet, columnName);
        if (column == null)
        {
            _log.Log("Missing column " + columnName);
        }

        var propertyBody = maps[i].Body;
        if (propertyBody is UnaryExpression && propertyBody.NodeType == ExpressionType.Convert)
        {
            propertyBody = ((UnaryExpression)propertyBody).Operand;
        }

        var propertyInfo = propertyBody as MemberExpression;
        if (propertyInfo != null)
        {
            var property = propertyInfo.Member as PropertyInfo;
            var val = property.GetValue(source);
            if (val != null)
            {
                sheet.Cells[row, column.Start.Column].Value = val;
            }
        }
        else if (typeof(TExportObject) == typeof(string))
        {
            sheet.Cells[row, column.Start.Column].Value = source;
        }
    }
}