Try this! 😁

[UIHint(UIHint.MediaFile)]
public virtual ContentReference CsvFile { get; set; }

public string GetCsvFileContent()
{
    if (!ContentReference.IsNullOrEmpty(CsvFile))
    {
        var contentLoader = ServiceLocator.Current.GetInstance<IContentLoader>();
        var contentFile = contentLoader.Get<MediaData>(CsvFile);
        using (var sr = new StreamReader(contentFile.BinaryData.OpenRead()))
        {
            return sr.ReadToEnd();
        }
    }
    return null;
}