无法投类型A至类型B. LINQ到实体仅支持铸造EDM原始或枚举类型

Question

我在我的项目首先使用EF代码，我有以下实体：

public class WorkcenterCapacity : ITimePeriodEntity 
{ 
    public int Id { get; set; } 
    public decimal AvailableCapacity { get; set; } 
    public DateTime FromTime { get; set; } 
    public DateTime ToTime { get; set; } 
} 
public interface ITimePeriodEntity 
{ 
    DateTime FromTime { get; set; } 
    DateTime ToTime { get; set; } 
} 

我用PredicateBuilder做一个动态的谓词。我定义以下通用类可用性目的：

public static class CropPredicateBuilder<T> where T : ITimePeriodEntity 
{ 
    public static Expression<Func<T, bool>> Creat(DateTime windowStart, 
                DateTime windowFinish) 
    { 
     var result = PredicateBuilder.False<T>(); 
     Expression<Func<T, bool>> completelyInWindowRanges = 
      x => x.FromTime >= windowStart && x.ToTime <= windowFinish; 
     Expression<Func<T, bool>> startIsInWindowRanges = 
      x => x.FromTime >= windowStart && x.FromTime <= windowFinish; 
     Expression<Func<T, bool>> finishIsInWindowRanges = 
      x => x.ToTime >= windowStart && x.ToTime <= windowFinish; 
     Expression<Func<T, bool>> overlapDateRangeWindow = 
      x => x.FromTime <= windowStart && x.ToTime >= windowFinish; 

     return result.Or(completelyInWindowRanges) 
      .Or(startIsInWindowRanges) 
      .Or(finishIsInWindowRanges) 
      .Or(overlapDateRangeWindow); 
    } 
} 

，并用它如下：

var predicate = CropPredicateBuilder<WorkcenterCapacity> 
       .Creat(DateTime.Now,DateTime.Now.AddDays(10)); 

var workcenterCapacities = dbContext.WorkcenterCapacities 
      .AsNoTracking() 
      .Where(predicate) 
      .AsExpandable() 
      .ToList(); 

但是当我运行它，我得到以下错误：

Unable to cast the type 'WorkcenterCapacity' to type 'ITimePeriodEntity'. LINQ to Entities only supports casting EDM primitive or enumeration types.

哪有我解决这个问题？

Answer 1

尝试这样

where T : class, ITimePeriodEntity 

它想第一个约束是一流的。我认为这是肯定的。