I think I've found a way to fix it:
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FTPControlSocket.cs, line 239:
writer = new StreamWriter(stream);
changed to
writer = new StreamWriter(stream,System.Text.Encoding.Default);
Purpose: enabling transfer of files with filenames containing Danish characters
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FTPClient.cs:
Line 48: added
using System.Text;
Line 106: added
private static Encoding encoding = Encoding.Default;
line 1206:
StreamReader reader = new StreamReader(GetDataStream());
...changed to:
StreamReader reader = new StreamReader(GetDataStream(),encoding,true);
Purpose: Enabling proper transfer of filenames with Danish characters using "NLST" (Name List).
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At least it seems to work for me in my scenario...