1) Extract method:  

    private static string GetExportFilePath(string csvFilePath, DateTime date, string fileSuffix)
    {
        return string.Format("{0}{1:yyyy-MM-dd}-{2}.csv", csvFilePath, date, fileSuffix);
    }

2) Also I would add those `selectedExportPath` and `csvFilePath` as parameters to `Export` method. I hope they are not used anywhere. It is usually pretty subjective whether to add something as method parameters or leave it as class member, but here I would definitely add them as parameters because I also tend to move such methods out from the views and I assume this class is `View` since you have button click event handlers.