1

我有一个用于//主题信息的 Web UI，add并且edit这些delete数据保存在名为Subject. 在该表中，有诸如Id(PK)、SubjectCode、SubjectName等列Tutor...

Idfield 是主键，总是唯一的。

SubjectCode是一个varchar应该是唯一的字段（值CS1001等）

插入和更新数据时，我已经使用LINQ(C#) 验证了唯一性，如下所示。

bool isCodeExist = DbContext.Subject.Any(record => record.SubjectCode == subject.SubjectCode);

if (true == isCodeExist )
{
    // SubjectCode is already exist. Do not proceed.
    return -1;
}
else
{
    // Proceed...
}

这仅适用于插入。

有时更新时会出现错误，例如仅更新主题的导师姓名（或其他列）。感谢您对此的帮助。

UPDATE：更新操作的完整代码部分。

    public int EditSubject(Subject subject)
    {
        using (SMSEntities DbContext= new SMSEntities())
        {
            try
            {                    
                bool isCodeExist = DbContext.Subject.Any(record => record.SubjectCode == subject.SubjectCode);


                if (true == isCodeExist )
                {
                     // SubjectCode is already exist. Do not proceed.
                     return -1;
                }
                else
                {
                    // Create table object 
                    Subject theSubject = new Subject();

                    // Assign values from the domain entity obj from param
                    theSubject.SubjectCode = subject.SubjectCode;
                    theSubject.Tutor = subject.Tutor;       
                    theSubject.LastUpdatedDate = DateTime.Now;
                    // other value assignment also same....

                    // Save subject
                    DbContext.Subjects.Attach(theSubject);
                    DbContext.ObjectStateManager.ChangeObjectState(theSubject, EntityState.Modified);
                    DbContext.SaveChanges();

                    return 0;
                }
            }                
            catch (Exception)
            {
                // Log exception
                throw;
            }
        }
    }
4

1 回答 1

3

如果仅用于更新，则在您的谓词中您也应该检查 Id，如下所示：

bool isCodeExist = DbContext.Subject.Any(record => 
                                         record.SubjectCode == subject.SubjectCode &&
                                         record.Id != subject.Id);

更新：

但如果它是一个 UpdateOrInsert ：

public int EditSubject(Subject subject)
{
    using (SMSEntities DbContext= new SMSEntities())
    {
        try
           {                    
            var theSubject = DbContext.Subject.SingelOrDefault(record => record.SubjectCode == subject.SubjectCode);

            if (theSubject != null)
            {
                 // A subject with the same SubjectCode exists.
                 if(existingSubject.Id != Subject.Id)
                 {
                     //It's another subject.
                     return -1;
                 }// else it's the same Subject so we may want to update it.
            }
            else //Subject does not exist.
            {
                // Create table object 
                theSubject = new Subject();
            }
            // Assign values from the domain entity obj from param
            theSubject.SubjectCode = subject.SubjectCode;
            theSubject.Tutor = subject.Tutor;       
            theSubject.LastUpdatedDate = DateTime.Now;
            // other value assignment also same....

            // Save subject
            DbContext.Subjects.Attach(theSubject);
            DbContext.ObjectStateManager.ChangeObjectState(theSubject, EntityState.Modified);
            DbContext.SaveChanges();

            return 0;
        }                
        catch (Exception)
        {
            // Log exception
            throw;
        }
    }
}

让我知道它是否有帮助。

于 2013-01-20T12:26:24.833 回答