在Linq中通過查詢創建動態組

Question

我有一個帶有4復選框的表格用於分組，當我想在where子句中創建LINQ動態查詢時，使用這樣的東西非常容易：

  query = query.where(x=>x.blah == blahblah).asQueryable();

但是我無法為Group by子句模擬這種類型的編碼。 我需要這樣的東西：

if(blah1==true)
    query = query.GroupBy(x=>x.Blah1).select(smthing);
if(blah2==true)
    query = query.GroupBy(x=>x.Blah2).select(smthing);
if(blah3==true)
    query = query.GroupBy(x=>x.Blah3).select(smthing);
 ....

我該如何查詢？ stackoverflow中的某些帖子顯示了誤解代碼，例如Expression>。 請給我展示一種簡單且適用的方法。

Answer 1

可能這不是正確的做事方式，但是使用反射可以做事。 因此，您所需GroupBy就是確定屬性名稱並將其傳遞給GroupBy 。

class Person
{
    public string Name { get; set; }
    public int Wage { get; set; }
    public int Age { get; set; }
    public override string ToString() =>
        $"Name: {Name}, Wage: {Wage}, Age: {Age}";
}

var list = new List<Person>
{
    new Person { Name = "Name1", Wage = 1, Age = 1},
    new Person { Name = "Name1", Wage = 2, Age = 2},
    new Person { Name = "Name2", Wage = 2, Age = 2},
    new Person { Name = "Name3", Wage = 2, Age = 2},
    new Person { Name = "Name3", Wage = 2, Age = 2},
    new Person { Name = "Name4", Wage = 2, Age = 2},
    new Person { Name = "Name4", Wage = 2, Age = 2}
};

var x = list.GroupBy(p => p.GetType().GetProperty("Name").GetValue(p));

foreach(var z in x)
{
    WriteLine(z.Key);
    foreach(var p in z)
    {
        WriteLine("\t" + p);
    }
}

/*
    Output:

Name1
      Name: Name1, Wage: 1, Age: 1
      Name: Name1, Wage: 2, Age: 2
Name2
      Name: Name2, Wage: 2, Age: 2
Name3
      Name: Name3, Wage: 2, Age: 2
      Name: Name3, Wage: 2, Age: 2
Name4
      Name: Name4, Wage: 2, Age: 2
      Name: Name4, Wage: 2, Age: 2
*/