Question

In my asp.net application I have two pages like new students and edit students. On the new student page I am passing general details like first name, last name, mobile number, email and register number.

Here RegNo should be unique. I am using Entity Framework for database connection. I’m checking with the condition to avoid the same RegNo being entered, like:

DataObject.Entities dataEntities = new DataObject.Entities();

if (!dataEntities.Students.Any(s => s.RegNo == RegNo))
{
    // my code here.
}

The same way for edit option, when try to change the RegNo. If it is allotted to some other student, it should not go into the update code.

I know if I use the same condition here, it will fail, because the RegNo is there in the database for this student (the one am trying to update), so if the RegNo is allotted for this particular student and not for other students it should be accepted, otherwise should go to else part.

I don’t know how to check this using Entity Framework. Can anyone help me,please?

I’ve a column StudentId, it’s an autoincrement column

I tried like

if (!dataEntities.Students.Any(s => s.RegNo == RegNo && s.StudentId != StudentId))
{
}

still it’s not working…..

Answer 1

I just declared an object for the student table and tried like,

DataObject.Student student = dataEntities.Students.First(s => s.StudentId == 
                                                                     StudentId);

 if (!dataEntities.Students.Any(s => s.RegNo == RegNo &&
                                             s.StudentId != student.StudentId))
 {

 }
 else
 {
    throw new exception("RegNo already exists!");
 }

and its working for me