Remove items from an Object [] that are contained in a custom class array

I have an array of custom items and then I have an array of objects object[], returned by a function. This object array is indeed of the same Clients type but it is returned as array of object type (I cannot edit this aspect).

I tried with an explicit cast, but I get an exception at runtime saying: cannot convert object[] to clients[].

My goal, once I have both arrays, would be to remove from one list the items that are present in the other list too and make an union, in order to have a unique list.

var client = getClients().ToArray();           //Is an array of Clients[]
var normalSearch = getDuplicates().ToArray();  //Is an array of objec开发者_JAVA技巧t[]


//This what I try to achieve,but being object, I cannot invoke "c.ContactId" (Line 4)
var uni = (from c in normalSearch
           where !(from d in dupes
                   select d.ContactId)
                   .Contains(c.ContactId)
           select c).ToArray();

I know that in Linq Union() could exclude automatically duplicate if a primitive type is used, otherwise an extension has to be developed with custom types. But I have not access to the rest of the code, therefore no possibility to change the logic elsewhere.

getDuplicates().Cast<Client>();

var uni = client.Union(normalSearch.Cast<Client>())
    .DistinctBy(c => c.ContractId);

The DistinctBy is in MoreLinq.

If you can't use MoreLinq, you can simply do

var uni = client.Union(normalSearch.Cast<Client>())
    .GroupBy(c => c.ContractId)
    .Select(g => g.First());

Which is basically their implementation of it.

You can cast the duplicates to clients using linq, and then create a comparer class. I copy and pasted this from the msdn documentation, it may need to be tweaked

var normalSearch = getDuplicates().ToArray().Cast<Clients>();
var client = getClients().ToArray();

var unique = client.Union(normalSearch, new ClientsComparer());

public class ClientsComparer : IEqualityComparer<Clients>
{
    public bool Equals(Clients x, Clients y)
    {

        //Check whether the compared objects reference the same data.
        if (Object.ReferenceEquals(x, y)) return true;

        //Check whether any of the compared objects is null.
        if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null))
            return false;

        //Check whether the products' properties are equal.
        return x.ContactId == y.ContactId;
    }

    // If Equals() returns true for a pair of objects 
    // then GetHashCode() must return the same value for these objects.

    public int GetHashCode(Client client)
    {
        //Check whether the object is null
        if (Object.ReferenceEquals(product, null)) return 0;

        //Calculate the hash code for the product.
        return client.ContactId.GetHashCode();
    }

}