Expression> and Sql IN

Question

I want to use expression trees to make filters with entity framework.

So this is my types

public class Type1
{
    public string Name { get; set; }
}

public class Type2
{
    public IEnumerable<string> Names { get; set; }
}

and this is my specification

public Expression<Func<Entities.Type1, bool>> MyExpression(Type2 filter)
{
    //something like where name in (name[0], name[1], ... name[n])
}

I need transform this in something like Sql where in.

How can I do it, and what's the best form?

How can I make Entity Framework understand my arbitrary expression in the way I want?

And the question is? Is it "How do I make Entity Framework interpret my arbitrary expression in the way I want?"? — Jodrell, Feb 05 '16 at 16:02
What's wrong with `type1s.Where(t1 => filter.Names.Contains(t1.Name))`? — Rhumborl, Feb 05 '16 at 16:10

score 3 · Accepted Answer · answered Feb 05 '16 at 16:09

3

You can do it simply like this:

public Expression<Func<Type1, bool>> MyExpression(Type2 filter)
{
    return x => filter.Names.Contains(x.Name);
}

answered Feb 05 '16 at 16:09

Yacoub Massad

27,509
2
36
62

score 1 · Answer 2 · edited May 23 '17 at 12:24

1

You can try this:

public Expression<Func<Type1, bool>> MyExpression(Type2 filter)
{
    Expression<Func<Type1, bool>> expression =  t1 => filter.Names.Contains(t1.Name);
    return expression;
}

In this post you can find good explanation why you can convert a lambda expression to an expression tree.

edited May 23 '17 at 12:24

Community

1
1

answered Feb 05 '16 at 16:09

ocuenca

38,548
11
89
102

Expression> and Sql IN

2 Answers2