如何在C#中使用Linq来做到这一点？

Question

I have this Object:

class Car 
{
    public int Id { get; set; }
    public string Name { get; set; }
    public Color Color { get; set; }
}

public enum Color
{
    Red = 1,
    Blue = 2,
    Pink = 3,
    Orange = 4,
}
    

How to create a linq query if I want take objects which have Red and Blue values:

query = query.Where(at => at.Color == Color.Red + Color.Blue);

Answer 1

If I take you at face value, and you want cars to be able to have more than one colour then you need to change your enum to use the Flags attribute.

Like this:

[Flags]
public enum Color
{
    Red = 1,
    Blue = 2,
    Pink = 4,
    Orange = 8,
}

Now I can write this code:

var cars = new []
{
    new Car() { Name = "Red & Orange", Color = Color.Red | Color.Orange },
    new Car() { Name = "Red & Blue", Color = Color.Red | Color.Blue },
};

var query = cars.Where(at => at.Color == (Color.Red | Color.Blue));

That, indeed, returns just the "Red & Blue" car.

However, if you meant or rather than and then you don't need to change your enum and the following is what you need:

query = query.Where(at => at.Color == Color.Red || at.Color == Color.Blue);

Answer 2

Either you can make the query with ||or operator

query = query.Where(at => at.Color == Color.Red 
    || at.Color == Color.Blue);

Or create an Color array to check whether the value is within the array.

query = query.Where(at => (new Color[] { Color.Red, Color.Blue }).Contains(at.Color));