Yes, you can just declare it in class level and use it wherever you want.
public class MyClass
{
dbEntities ctx = new dbEntities()
private void MyFunction()
{
}
}
If you do like this, then the object will not get disposed until Garbage Collector comes and disposes it.
But if you use
using Statement[
^], then just after the using statement the object will get disposed, which will be a performance advantage for your application.