指定的强制转换在将int强制转换为字节时无效

如何解决指定的强制转换在将int强制转换为字节时无效

| 我有一个名为：AttachmentType的实体，该实体具有字节的ShowDuringRegistration属性 执行此行时，我总是会看到此错误：无论我发送一个字节作为参数，指定的转换都是无效的

Repository<AttachmentType>.FindBySpecification(new AttachmentSearchSpecification()
    .WithTraceCodeOrNationalNumber(traceCodeString)
    .WithAttachmentTypeShowDuringRegistration(false))
    .Select(p=>new attachmentTypeModel()
     {
       Id=p.Id,Title=p.Title
     })
    .ToList();

 public AttachmentSearchSpecification WithAttachmentTypeShowDuringRegistration(bool showDuringRegistration=false)
 {          
      AddExpression(p => p.AttachmentType.ShowDuringRegistration == (showDuringRegistration ? 1 : 0));
      return this;
 }

即使我向WithAttachmentTypeShowDuringRegistration方法发送了一个字节并将ShowDuringRegistration与该属性进行比较也无法正常工作

byte b=0;
Repository<AttachmentType>.FindBySpecification(new AttachmentSearchSpecification()
    .WithTraceCodeOrNationalNumber(traceCodeString)
    .WithAttachmentTypeShowDuringRegistration(b))
    .Select(p=> new attachmentTypeModel()
     {
       Id=p.Id,Title=p.Title
     })
    .ToList();

public AttachmentSearchSpecification WithAttachmentTypeShowDuringRegistration(byte showDuringRegistration)
{
    AddExpression(p => p.AttachmentType.ShowDuringRegistration == showDuringRegistration)
    return this;
}

这是错误引发的时间：

select cast(count(*) as INT) 
as col_0_0_ from EmploymentRegistration.[Attachment]
attachment0_,EmploymentRegistration.[Demand] demand1_,EmploymentRegistration.[AttachmentType] attachment5_ where ttachment0_.DemandId=demand1_.DemandId 
 and demand1_.PersonId=person3_.PartyId and person3_.PartyId=birthcerti4_.PersonId and
 attachment0_.AttachmentTypeId=attachment5_.AttachmentTypeId 
 and (demand1_.TraceCode like (\'%\'+?+\'%\') or birthcerti4_.NationalNumber like (\'%\'+?+\'%\'))
 and   attachment5_.ShowDuringRegistration=?

内部异常：

{\"Specified cast is not valid.\"}

protected void AddExpression(Expression<Func<T,bool>> expression);  this method get an expeRSSion and append that expression to the linq query 



 public class AttachmentTypeMap : ClassMap<AttachmentType>
{
    public AttachmentTypeMap()
    {
        Schema(\"EmploymentRegistration\");

        Id(p => p.Id);//int identity

        Map(p => p.Title);//string

        Map(p => p.ShowDuringRegistration);//byte

        Map(p => p.ScriptName)
            .Length(100);

        References(p => p.EmploymentLicense);
    }
}`

通过执行这样的简单查询：

 Repository<AttachmentType>.FindAll().Where(p=>p.ShowDuringRegistration==(byte)1).Tolist();

这样会产生     从中选择cast（count（*）作为INT）作为col_0_0_     EmploymentRegistration。[AttachmentType]附件0_左外部联接     就业登记。 [EmploymentLicense]就业1_      在附件0_.EmploymentLicenseId = employment1_.EmploymentLicenseId上，      attachment0_.ShowDuringRegistration =？ 当我想知道返回值的数量时

int _totalItems = Query.Count();  //Query is IQueryable<T>

我会再次看到错误 即使只是执行此查询，错误也会像以前一样引发：

//ShowDuringRegistration  is byte?
var data= Repository<AttachmentType>.Find(p => p.ShowDuringRegistration == 0)
                                    .ToList();
public interface IRepository<T> where T : class
{

   IQueryable<T> Find();

    IQueryable<T> Find(object id);

    IQueryable<T> FindBySpecification(ISpecification<T> specification);

    IQueryable<T> Find(Expression<Func<T,bool>> expression);

}


 public static class Repository<T> where T : class
{

private static IRepository<T> Current
    {
        get { return UnitOfWork.GetRepository<T>(); }
    }

 public static IQueryable<T> Find(Expression<Func<T,bool>> expression)
    {
        return Current.Find(expression);
    }

 public static IList<T> FindAll(Expression<Func<T,bool>> expression)
    {
        return Current.FindAll(expression);
    }

}

    

解决方法

您实际上并没有使用字节-您正在使用

int

。它通常在C＃中工作，因为将ѭ9提升为

int

，然后进行比较。尝试以下方法：

public AttachmentSearchSpecification WithAttachmentTypeShowDuringRegistration
    (bool showDuringRegistration=false)
{
    byte value = showDuringRegistration ? (byte) 1 : (byte) 0;

    AddExpression(p => p.AttachmentType.ShowDuringRegistration == value);
    return this;
}