'Union two list by property

I would like to merge two list without duplicates. It should distinct only by one property.

I have a class:

public class Test
{
    public int Id { get; set; }
    public string Prop { get; set; }
    public string Type { get; set; }
}

I have two lists which I would like to merge without duplicates by Type. So, firstly I want to take everything from list 1 and then from list 2 when Type doesn't exist in list 1.

I've tried union.

c++sharp.netlinqlistienumerable


Solution 1:[1]

You've to use IEqualityComparer. See at : https://msdn.microsoft.com/en-us/library/ms132151%28v=vs.110%29.aspx?f=255&MSPPError=-2147217396

class Compare : IEqualityComparer<Test>
{
    public bool Equals(Test x, Test y)
    {
        return x.Id == y.Id;
    }
    public int GetHashCode(Test codeh)
    {
        return codeh.Id.GetHashCode();
    }
}

Then use

var union = list1.Union(list2).Distinct(new Compare()).ToList();

Solution 2:[2]

Using .NET 6 or higher, you can use the UnionBy() method which will merge 2 lists excluding duplicates by a property :

var mergedLists = firstList.UnionBy(secondList, u => u.property).ToList();

For more informations : Microsoft doc

Sources

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Source: Stack Overflow

Solution Source
Solution 1 M.S.
Solution 2 twllm_dvlp

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