savechanges inserts only one record in table code example
Example: insert multiple records on the Database in Entity Framework Core
var dept1 = new Department() { Name = "Development" };
var dept2 = new Department() { Name = "HR" };
var dept3 = new Department() { Name = "Marketing" };
using (var context = new CompanyContext())
{
context.Department.AddRange(dept1, dept2, dept3);
context.SaveChanges();
}