无法将类型list<schoolfee.feecollection>隐式转换为list<student.feecollection>错误

BO.SchoolFee.FeeCollection BO.Student.FeeCollection

FeeCollections

class FeeCollection : IEnumerable<Fee> {...}

IEnumerable<Fee> ICollection<Fee>

IEnumerable<fee>

FeeCollection(IEnumerable<Fee> fees)
{
    foreach (Fee fee in fees)
       this.Add(fee);
}

extension method demystified

static Student.FeeCollection ToStudentFeeCollection(this IEnumerable<Fee> fees)
{
      Student.FeeCollection feeCollection = new Student.FeeCollection();
      foreach (Fee fee in fees)
      {
          feeCollection.Add(fee);
      }
      return feeCollection;
}

static Student.FeeCollection ToStudentFeeCollection(this SchoolFee.Collection schoolFeeCollection)
{
     IEnumerable<Fee> schoolFees = schoolFeeCollection;
     return schoolFees.ToStudentFees();

     // or if you don't want to implement IEnumerable<Fee>:
     var studentFeeCollection = new Student.FeeCollection();
     foreach (var schoolFee in schoolFeeCollection.GetFees())
     {
          studentFeeCollection.Add(schoolFee);
     }
}

List<School.FeeCollection> schoolFeeCollections = ...
// convert every schoolFeeCollection to a StudentFeeCollection:
List<Student.FeeCollection> studentFeeCollections = schoolFeeCollections
    .Select(schoolFeeCollection => schoolFeeCollection.ToStudentFeeCollection())
    .ToList();

Student.Fee ToStudentFee(this School.Fee schoolFee)
{
    return new Student.Fee()
    {
        Description = schoolFee.Description,
        Amount = schoolFee.Amount,
        DueDate = schoolFee.DueDate,
    };
}

SISBOLibrary.BO.SchoolFee.FeesCollection SISBOLibrary.BO.Student.FeesCollection paymentlist

studentObj.FeesCollectionPending = paymentlist
    .Select(p => new SISBOLibrary.BO.Student.FeesCollection { 
        field1 = p.field1,
        field2 = p.field2,
        //and so on
    })
    .ToList(); 

Automapper