C# Lambda WhereIf 或语句

Question

我有许多未知的搜索参数需要评估。我最多只有 5 个搜索级别，目前只显示 3 个级别。我一直在尝试使用 WhereIf 扩展，但也许那不是最好的方法。我更喜欢 lambda 或 linq 语句中的解决方案。这是一个模型:

考虑:

Animal_ID    Breed     Color    Age   Weight
1            Poodle    White      3     10
2            Shepard   Brown      4     15
3            Afghan    Brown      9     40
4            Terrier   White      7     25
5            Maltese   White      12    14

请原谅，我知道这还不完整。我开始这样做，但后来意识到这会变得复杂。

List<Animal> animals = db.Animals
  //I know I can do this.   
  //.WhereIf(!String.IsNullOrEmpty("Search"), x => (x.Color == "white") || (x.Breed == "terrier"))             
  //I want "OR" here
  .WhereIf(!String.IsNullOrEmpty("Search_1_IsSomething"), x => (x.Color == "white")) // OR
  .WhereIf(!String.IsNullOrEmpty("Search_2_OR_IsSomething"), x => (x.Breed == "terrier"))
  .ToList();

提前致谢。

Answer 1

您完全可以在没有 WhereIf 的情况下完成同样的事情。

var result = !String.IsNullOrEmpty(searchVar) ? 
    animals.Where(x => x.Color == "white" || 
    x.Breed == "terrier") : new List<Animal>();

不过，您可能只希望它搜索传入的搜索词。

var result = !String.IsNullOrEmpty(searchVar) ? 
        animals.Where(x => x.Color == searchVar || 
        x.Breed == searchVar) : new List<Animal>(); //or return full list (animals) if search term is null 

编辑:在 linqpad 中进行测试，似乎运行良好。

void Main()
{
    SearchAnimals("white").Dump();
}

public List<Animal> SearchAnimals(string searchVar)
{
    var animals = new List<Animal>()
    {
        new Animal { Animal_ID = 1, Color = "black", Breed = "other" },
        new Animal { Animal_ID = 2, Color = "white", Breed = "other" },
        new Animal { Animal_ID = 3, Color = "blue", Breed = "terrier" },
        new Animal { Animal_ID = 4, Color = "green", Breed = "other" }
    };

    var result = !String.IsNullOrEmpty(searchVar) ? 
        animals.Where(x => x.Color == "white" || 
        x.Breed == "terrier") : new List<Animal>();

    return result.ToList();
}

public class Animal
{
    public int Animal_ID { get; set; }
    public string Color { get; set; }
    public string Breed { get; set; }
}

返回:

List<Animal> (2 items)

Animal_ID   Color    Breed
2           white    other 
3           blue     terrier