score:1

list<string> result = dtfilter.asenumerable()
                              .select(r => r.field<string>(0))
                              .select(s => s.replace("0", " "))
                              .tolist();

score:1

var result = dtfilter
                .asenumerable()
                .select(r => r.field<string>(0))
                .select(s => string.join("", 
                                     s.select((x, i) => x == '1' 
                                                        ? (i+1).tostring()
                                                        : " "))
                 );

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