StreamReader C# does not read å, ä, ö

I have a StreamReader reading a file like below for reading a .csv file:

using (StreamReader sr = new StreamReader(filePath, System.Text.Encoding.GetEncoding("iso-8859-1")))
{
    string line = string.Empty;
    line = sr.ReadLine()
}

The first line of the file is: å ä ö Ü (for testing purposes). However, when I try to read the file C# does not read the characters as it should:

Any idea why that is?

Remove encoding or select the right one. I am using this syntax without any problem

    string str = string.Empty;
    using (StreamReader r = new StreamReader(@"C:\..."))
        str = r.ReadToEnd();

ouput

å ä ö Ü