I made this method and other attempts. With the table filled, okay, but with the table without data, it is giving error:
public int GeraIdBalanca()
{
int chave = 0;
var obj = contexto.Balancas.Max().IdBalanca;
if (obj == 0)
chave = 1;
else
chave = obj + 1;
return chave;
}
I tried the table with information, I can bring the ID, but with the table zeroed, newly created gives me error.
The whole code can be written like this
public int GeraIdBalanca() => contexto.Balancas.Max()?.IdBalanca + 1 ?? 1;
Your problem is because you need to check if the return of Max is not null before you try to access the IdBalanca property.
var obj = contexto.Balancas.Max()?.IdBalanca ?? 1;
If you are using the Entity Framework, I already stress that your approach does not work and does not even make sense.
In EF, the method would need to be
public int GeraIdBalanca() => contexto.Balancas.Any() ? contexto.Balancas.Max(b => b.id) + 1 : 1;
Or, in a normal method
public int GeraIdBalanca()
{
return contexto.Balancas.Any() ? contexto.Balancas.Max(b => b.id) + 1 : 1;
}
I believe it can be done like this:
var obj = contexto.Balancas.Max(b => b.IdBalanca);
int chave = (obj == null ? 1 : obj + 1);
return chave;
You can use a Default solution for when your table did not have data.
public int GeraIdBalanca()
{
return contexto.Balancas.Select(m => m.IdBalanca).DefaultIfEmpty(0).Max() + 1;
}