Question

我的问题很难解决。我需要你的帮助这个问题。在codefirst中有很多关系。但我无法解决这个问题。我想使用Predicate func。但我无法解决它？如何使用“Method（Predicate func）”

     public int Method<T>(Predicate<T> func)
    {


        var s1 = this.Uow.X.GetAll().Where(func)
                       .SelectMany(a => a.OrganizationalUnits.Where(q => Identity.Y.Contains(q.Z)))
                      .GroupBy(t => t, (k, g) => new
                      {
                          Tag = k,
                          Count = g.Count()
                      })
                      .OrderByDescending(g => g.Count);


        var s2 = this.Uow.X.GetAll().Where(func)
                        .SelectMany(a => a.Classes.Where(q => Identity.Y.Contains(q.K)))
                        .GroupBy(t => t, (k, g) => new
                        {
                            Tag = k,
                            Count = g.Count()
                        })
                        .OrderByDescending(g => g.Count);


        var s3 = this.Uow.X.GetAll().Where(func)
                        .SelectMany(a => a.Courses.Where(q => Identity.Y.Contains(q.L)))
                        .GroupBy(t => t, (k, g) => new
                        {
                            Tag = k,
                            Count = g.Count()
                        })
                        .OrderByDescending(g => g.Count);



        return s1.ToString().Count() + s2.ToString().Count() + s3.ToString().Count();
    }

Answer 1

这是做到这一点的方法。我还删除了最后一行的ToString()，因为您不需要将对象作为字符串来计算它。

这样打电话：int result = Method<TypeGoesHere>(p => p == aValue);

 public int Method<T>(Expression<Func<T, Boolean>> Predicate)
{


    var s1 = this.Uow.X.GetAll().Where(Predicate)
                   .SelectMany(a => a.OrganizationalUnits.Where(q => Identity.Y.Contains(q.Z)))
                  .GroupBy(t => t, (k, g) => new
                  {
                      Tag = k,
                      Count = g.Count()
                  })
                  .OrderByDescending(g => g.Count);


    var s2 = this.Uow.X.GetAll().Where(Predicate)
                    .SelectMany(a => a.Classes.Where(q => Identity.Y.Contains(q.K)))
                    .GroupBy(t => t, (k, g) => new
                    {
                        Tag = k,
                        Count = g.Count()
                    })
                    .OrderByDescending(g => g.Count);


    var s3 = this.Uow.X.GetAll().Where(Predicate)
                    .SelectMany(a => a.Courses.Where(q => Identity.Y.Contains(q.L)))
                    .GroupBy(t => t, (k, g) => new
                    {
                        Tag = k,
                        Count = g.Count()
                    })
                    .OrderByDescending(g => g.Count);

    return s1.Count() + s2.Count() + s3.Count();
}

我认为你可能想要一个this类型的扩展方法。它看起来像这样（如果thisType是this的类型）。这不需要是模板，因为您（但不是我）知道X.GetAll()的类型。我猜测列表<int>会产生T int。我还将代码更改为更简洁，但具有相同的功能。（这可能是你原来的代码做错了，但这也是做同样的事情。）

这样打电话：

thisType something = new something();
someType aValue = X; // don't know the type here.

// do stuff with something

int result = something.Method(p => p == aValue);

代码：

public static int Method(this thisType me, Expression<Func<someType, Boolean>> Predicate)
{
    var allOfEm = me.Uow.X.GetAll().Where(Predicate);

    var s1 = allOfEm
              .SelectMany(a => a.OrganizationalUnits.Where(q => Identity.Y.Contains(q.Z)))
              .Distinct();

    var s2 = allOfEm
              .SelectMany(a => a.Classes.Where(q => Identity.Y.Contains(q.K)))
              .Distinct();

    var s3 = allOfEm
              .SelectMany(a => a.Courses.Where(q => Identity.Y.Contains(q.L)))
              .Distinct();

    return s1.Count() + s2.Count() + s3.Count();
}

如何在多对多关系实体框架中使用谓词方法linq lambda表达式？

1 个答案: