Linq – combine items of two lists

linq

I want to combine items of two string list but do not want repeated items

List<string> l1 = new List<string>() { "A", "B", "C", "D"};
List<string> l2 = new List<string>() { "B", "E", "G", "D"};

Result: A, B, C, D, E, G

How can i achieve this?

Best Solution

Use the Union and Distinct operators:

var newList = l1.Union(l2).Distinct().ToList();

Related Solutions

C# – How would you do a “not in” query with LINQ

You want the Except operator.

var answer = list1.Except(list2);

Better explanation here: https://docs.microsoft.com/archive/blogs/charlie/linq-farm-more-on-set-operators

NOTE: This technique works best for primitive types only, since you have to implement an IEqualityComparer to use the Except method with complex types.

.net – Which method performs better: .Any() vs .Count() > 0

If you are starting with something that has a .Length or .Count (such as ICollection<T>, IList<T>, List<T>, etc) - then this will be the fastest option, since it doesn't need to go through the GetEnumerator()/MoveNext()/Dispose() sequence required by Any() to check for a non-empty IEnumerable<T> sequence.

For just IEnumerable<T>, then Any() will generally be quicker, as it only has to look at one iteration. However, note that the LINQ-to-Objects implementation of Count() does check for ICollection<T> (using .Count as an optimisation) - so if your underlying data-source is directly a list/collection, there won't be a huge difference. Don't ask me why it doesn't use the non-generic ICollection...

Of course, if you have used LINQ to filter it etc (Where etc), you will have an iterator-block based sequence, and so this ICollection<T> optimisation is useless.

In general with IEnumerable<T> : stick with Any() ;-p

Best Solution

Related Solutions

C# – How would you do a “not in” query with LINQ

.net – Which method performs better: .Any() vs .Count() > 0

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