C# - 比较列表<t>到动态列表

Question

I have a dynamic list

            var myNames = new List<dynamic>();

Based on some conditions while iterating through my collection, I am adding 2 columns Name and Address to the dynamic list along with some data

            myNames.Add(new
                    {
                        Name = MyCollection[i].<someName>,
                        Address = MyCollection[i].<someAddress>
                    });

Now I have a generic list called dbNames which contains a list of Names retrieved from database. My requirement is to iterate through dbNames for 5 times. Get the first (occurrence of a) name that exist in dbNames but not in myNames and add it to myNames.

Actually I am not able to figure out how to query the collection fetch the list of Names that exist in dbNames but not in myNames. I tried below

someName = dbNames.Where(d => !((IEnumerable<dynamic>)myNames.Contains(b=> d== (string)b.Name)).FirstOrDefault();

I am getting an error: 'Cannot convert lamda expression to type dynamic and not able to overcome it despite trying in other ways.

Answer 1

try something like,

var x=dbNames.Where(p=>!myNames.Select(q=>q.Name).Contains(p)).ToList().Distinct().Take(5);

Add these names to dynamic list myNames the way you want.

Full Code:

public static void Main()
    {
        List<string> names=new List<string>{"A","xxx","B","C","D","yyy","E","F"};
        List<dynamic> dyn=new List<dynamic>();
        dynamic person = new ExpandoObject();
        person.Name="xxx";
        person.Address="ADD";
        dynamic person1 = new ExpandoObject();
        person1.Name="yyy";
        person1.Address="ADD";
        dyn.Add(person);
        dyn.Add(person1);

        var x=names.Where(p=>!dyn.Select(q=>q.Name).Contains(p)).ToList().Distinct().Take(5);
        foreach(var n in x)
        {
            Console.WriteLine(n);
        }
    }

Answer 2

The Contains() method just does not accept a lambda expression, that's what the error says.

You can use Any() instead, and you can omit the Where() expression:

someName = dbNames.FirstOrDefault(dbName => !(myNames.Any(b => dbName == b.Name));