public static bool IsItNew(BloggingContext context, Blog blog) => context.Blogs.Find(blog.BlogId) == null;
private static void IsItNew()
{
Console.WriteLine();
Console.WriteLine("Show entity-specific check for key set:");
using (var context = new BloggingContext())
{
var blog = new Blog {
Url = "http://sample.com"
};
// Key is not set for a new entity
Console.WriteLine($" Blog entity is {(IsItNew(blog) ? "new" : "existing")}.");
context.Add(blog);
context.SaveChanges();
// Key is now set
Console.WriteLine($" Blog entity is {(IsItNew(blog) ? "new" : "existing")}.");
}
Console.WriteLine();
Console.WriteLine("Show general IsKeySet:");
using (var context = new BloggingContext())
{
var blog = new Blog {
Url = "http://sample.com"
};
// Key is not set for a new entity
Console.WriteLine($" Blog entity is {(IsItNew(context, (object)blog) ? "new" : "existing")}.");
context.Add(blog);
context.SaveChanges();
// Key is now set
Console.WriteLine($" Blog entity is {(IsItNew(context, (object)blog) ? "new" : "existing")}.");
}
Console.WriteLine();
Console.WriteLine("Show key set on Add:");
using (var context = new BloggingContext())
{
var blog = new Blog {
Url = "http://sample.com"
};
// Key is not set for a new entity
Console.WriteLine($" Blog entity is {(IsItNew(context, (object)blog) ? "new" : "existing")}.");
context.Add(blog);
// Key is set as soon as Add assigns a key, even if it is temporary
Console.WriteLine($" Blog entity is {(IsItNew(context, (object)blog) ? "new" : "existing")}.");
}
Console.WriteLine();
Console.WriteLine("Show using query to check for new entity:");
using (var context = new BloggingContext())
{
var blog = new Blog {
Url = "http://sample.com"
};
Console.WriteLine($" Blog entity is {(IsItNew(context, blog) ? "new" : "existing")}.");
context.Add(blog);
context.SaveChanges();
Console.WriteLine($" Blog entity is {(IsItNew(context, blog) ? "new" : "existing")}.");
}
}