Using LINQ to get a list of items where the item contains a part of an item from another list

Question

Having a list of models:

List<string> models = new List<string>
{
    "abcd1234",
    "xycd9999",
    "zzz999z",
    "ros7777"
};

Having a filterer list:

List<string> filterer = new List<string>
    {
        "cd",
        "9999"
    };

I am trying using LINQ to get all the models that contains as part of their name the filterer items.

For this example:

1. "abcd1234" and "xycd9999" contains "cd"
2. "xycd9999" contains "9999"

therefore the LINQ operation will return a list of the two items: "abcd1234" and "xycd9999".

var filteredList = models
                   .Where(m => m.Contains("/*HERE WILL BE THE FILTERER ITEMS*/"))
                   .Distinct()
                   .ToList(); 

What is the correct syntax?

Answer 1

var filteredList = models
    .Where(x => filterer.Any(y => x.Contains(y))
    .ToList();

Distinct serves no purpose here, as the Where call doesn't introduce duplicates (unless of course models has duplicate values, and you want to remove those duplicates).

Answer 2

"Or" equivalent in Linq Where() lambda expression

Try to use PredicateBuilder as the link goes:

public static class PredicateBuilder
{
    public static Expression<Func<T, bool>> True<T> ()  { return f => true;  }
    public static Expression<Func<T, bool>> False<T> () { return f => false; }

    public static Expression<Func<T, bool>> Or<T> (this Expression<Func<T, bool>> expr1,
                                                      Expression<Func<T, bool>> expr2)
    {
        var invokedExpr = Expression.Invoke (expr2, expr1.Parameters.Cast<Expression> ());
        return Expression.Lambda<Func<T, bool>>
           (Expression.OrElse (expr1.Body, invokedExpr), expr1.Parameters);
    }

    public static Expression<Func<T, bool>> And<T> (this Expression<Func<T, bool>> expr1,
                                                  Expression<Func<T, bool>> expr2)
    {
        var invokedExpr = Expression.Invoke (expr2, expr1.Parameters.Cast<Expression> ());
        return Expression.Lambda<Func<T, bool>>
           (Expression.AndAlso (expr1.Body, invokedExpr), expr1.Parameters);
    }
}

In your case:

List<string> models = new List<string>
{
    "abcd1234",
    "xycd9999",
    "zzz999z",
    "ros7777"
};
List<string> filterer = new List<string>
{
    "cd",
    "9999"
};
var predicate = PredicateBuilder.False<string>();

foreach (string filter in filterer)
{
    predicate = predicate.Or(f => f.Contains(filter));
}

var filteredList = models.AsQueryable().Where(predicate).ToList();