FileEncoding.cs

/// From https://www.codeproject.com/Tips/1231324/How-to-Get-a-Files-Encoding-with-Csharp

/// <summary
/// Get File's Encoding
/// </summary>
/// <param name="filename">The path to the file
private static Encoding GetEncoding(string filename)
{
    // This is a direct quote from MSDN:  
    // The CurrentEncoding value can be different after the first
    // call to any Read method of StreamReader, since encoding
    // autodetection is not done until the first call to a Read method.

    using (var reader = new StreamReader(filename, Encoding.Default, true))
    {
        if (reader.Peek() >= 0) // you need this!
            reader.Read();

        return reader.CurrentEncoding;
    }
}