StreamWriter Problem with encoding UTF-7

I have a text file in UTF-开发者_开发技巧7, I would like to create another file with same data like this :

    using (var sw = new StreamWriter(@"D:\toto.csv.copy", false, Encoding.UTF7))
    {
        using (var sr = new StreamReader(@"D:\toto.csv", Encoding.UTF7))
        {
            string line;
            while (null != (line = sr.ReadLine()))
            {
                sw.WriteLine(line);
            }
        }
    }

In the original file the first line is : ¤TEST¤ In the copy file, the first line is : +AKQ-TEST+AKQ-

the original file is in UTF-7, when I watch the line variable in debug mode, I can see "¤TEST¤" in line variable.

Can you help me please ?

Many thanks

Try using a custom encoding on the writer to allow use of optional characters in the output.

UTF7Encoding allowOptionals = new UTF7Encoding(true);

using (var sw = new StreamWriter(@"D:\toto.csv.copy", false, allowOptionals))
{
    using (var sr = new StreamReader(@"D:\toto.csv", Encoding.UTF7))
    {
        string line;
        while (null != (line = sr.ReadLine()))
        {
            sw.WriteLine(line);
        }
    }
}