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// try converting your list to a set and then back to a list.
// -- a set can not contain duplicates, so, dart removes it for us (^_^)
List duplicates = [ "foo", "foo", "bar", "bar", "baz", "baz"];
List noDuplicates = duplicates.toSet().toList();
print(noDuplicates); // [foo, bar, baz]
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List<int> duplicates = [1, 1, 2, 4, 2, 6, 8, 4, 5];
List<int> withoutDuplicates = duplicates.toSet().toList();
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List<String> countries = [
"Nepal",
"Nepal",
"USA",
"Canada",
"Canada",
"China",
"Russia",
];
var seen = Set<String>();
List<String> uniquelist = countries.where((country) => seen.add(country)).toList();
print(uniquelist);
//output: [Nepal, USA, Canada, China, Russia]