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POBuilding generic method for List<Enum>
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copied!<p>In my application, I have something like:</p> <pre><code>public enum Locations { LocationA, LocationB, LocationC } private List<Locations> _myLocations; public Int64 PackedLocations { get { return PackEnumList(this._myLocations); } } </code></pre> <p>So: an enum (backed by int), a List of those enum values, and a read-only property which returns the result of a method I've left out so far.</p> <p>That method, PackEnumList, is meant to give me a 64-bit integer where each BIT denotes whether the corresponding enum value was selected or not in a list of unique enum values. So in my example above, if _myLocations has only one item: {Locations.LocationA}, the result would be 1 (binary: ...00001), if we then add Locations.LocationC to that list, the result would be 5 (binary: ...000101). The implementation isn't important right now (but I'll include it below for completion/interest/feedback), but the signature of that method is:</p> <pre><code>public Int64 PackEnumList(List<Enum> listOfEnumValues) { ... } </code></pre> <p><strong>When I compile, I get an error that "the best overloaded method ... has some invalid arguments".</strong> </p> <p>I'm guessing this is because _myLocations is being seen as a List of int values, but I'd like PackEnumList() to work even if the enumeration being used were backed by something else, if possible.</p> <p>Is there a more appropriate way to make a method which will accept a List/Collection of any enumeration?</p> <p>For completeness, here's the rest of what I'm trying to do (these are static because they're in a shared utility class). These are completely untested yet (since I can't get past the compile error when calling the pack method), so take them with a grain of salt. And there might be a better way to do this, I'm doing this half to solve an interesting problem, and half because I think it is an interesting problem.</p> <pre><code> public static Int64 PackEnumList(List<Enum> listOfEnumValues) { BitArray bits = new BitArray(64, defaultValue: false); foreach (var value in listOfEnumValues) { // get integer value of each Enum in the List: int val = Convert.ToInt32(value); if (val >= 64) { // this enum has more options than we have bits, so cannot pack throw new Exception("Enum value out of range for packing: " + val.ToString()); } bits[val] = true; } var res = new Int64[1]; bits.CopyTo(res, 0); return res[0]; } // (this method is a little farther from the ideal: the resulting list will need // to be matched by the caller to the appropriate List of Enums by casting // each Int32 value to the Enum object in the list) public static List<Int32> UnpackEnumList(Int64 packedValue) { string binaryString = Convert.ToString(packedValue, 2); List<Int32> res = new List<Int32>(); for (int pos = 0; pos < binaryString.Length; pos++) { if (binaryString[binaryString.Length - pos - 1] == '1') { // bit is on res.Add(pos); } } return res; } </code></pre>

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