Linq select objects in Database exists Dictionary Keys

I want to query data from database by multiple primary keys at once by using Linq. However, I store my primary keys in Dictionary<int, string>

My dictionary

private Dictionary<int,string> dict = new Dictionary<int, string>
{
    {1, "Value 1"},
    {2, "Value 2"},
    {3, "Value 3"},
    {4, "Value 4"},
    {5, "Value 5"},
    {6, "Value 6"}

 };

In Raw SQL

SELECT * FROM Article WHERE ArticleId IN (1,2,3,4,5,6);

I have tried in Linq

var article = new NewsEntities().Articles;
var mainArticles = article.Where(a => dict.ContainsKey(a.ArticleId));

foreach (var mainArticle in mainArticles)
{
    Console.WriteLine(mainArticle.ArticleId);
}

The error I have got

System.NotSupportedException: 'LINQ to Entities does not recognize the method 'Boolean ContainsKey(Int32)' method, and this method cannot be translated into a store expression.'