How to access next and previous record with C# using Entity Framework

Question

I am developing a Windows Form application, with Entity Framework 6 + Mysql.

As is common in systems, I have in each form navigation buttons (First Record, Previous Record, Next Record, Last Record)

The doubt: there is some defined syntax (LINQ or Lambda), which takes me directly to the previous or next EXISTING record?

Example: I have the form displaying the record ID = 6. If I click the previous button, I should display the record 5. Likewise, the next one is record 7. However, if record 7 does not exist, record 8 should be displayed.

I can easily solve with programming logic, but I would like to know if there is a native language way to solve this type of operation.

Thank you.

Answer 1

You can use the following:

For item before ID 6:

Context.NomeEntidades.where(c=>c.ID<6).OrderByDescending(c=>c.ID).firstOrDefault();

And to the next:

Context.NomeEntidades.where(c=>c.ID>6).OrderBy(c=>c.ID).firstOrDefault();

Answer 2

The most elegant way I know is used to create pagination in ASP.NET MVC applications, using Skip() and Take():

var registroAtual = 6;
var registroAnterior = contexto.Entidade.Skip(registroAtual - 2).Take(1).FirstOrDefault();
var proximoRegistro = contexto.Entidade.Skip(registroAtual).Take(1).FirstOrDefault();

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EDIT

Suppose I want to specifically find the records before and next to Id 6:

var registroAnterior = contexto.Entidade.Where(e => e.Id <= 6).OrderByDescending(e => e.Id).Skip(1).Take(1).FirstOrDefault();
var proximoRegistro = contexto.Entidade.Where(e => e.Id >= 6).OrderBy(e => e.Id).Skip(1).Take(1).FirstOrDefault();