/*
* the DbContext is not aware of disconnected entities
* because entities were added or modified out of the scope of the current DbContext instance.
* So, you need to attach the disconnected entities to a context with appropriate EntityState
* in order to perform CUD (Create, Update, Delete) operations to the database.
*/
public static void AddUpdateEntityInDisconnectedScenario()
{
Console.WriteLine("*** AddUpdateEntityInDisconnectedScenario Starts ***");
// disconnected entities
var newStudent = new Student()
{
StudentName = "Bill"
};
var existingStudent = new Student()
{
StudentID = 10, StudentName = "Chris"
};
using (var context = new SchoolDBEntities())
{
//Log DB commands to console
context.Database.Log = Console.WriteLine;
context.Entry(newStudent).State = newStudent.StudentID == 0 ? EntityState.Added : EntityState.Modified;
context.Entry(existingStudent).State = existingStudent.StudentID == 0 ? EntityState.Added : EntityState.Modified;
context.SaveChanges(); // Executes Delete command
}
Console.WriteLine("*** AddUpdateEntityInDisconnectedScenario Ends ***");
}
/*
* FYI,
*
* ref: https://blogs.msdn.microsoft.com/marcelolr/2010/07/16/optimistic-and-pessimistic-concurrency-a-simple-explanation/
*/
public static void OptimisticConcurrency()
{
Console.WriteLine("*** OptimisticConcurrency Starts ***");
Student student = null;
using (var context = new SchoolDBEntities())
{
student = context.Students.First();
}
//Edit student name
student.StudentName = "Robin";
using (var context = new SchoolDBEntities())
{
context.Database.Log = Console.Write;
try
{
context.Entry(student).State = EntityState.Modified;
context.SaveChanges();
Console.WriteLine("Student saved successfully.");
}
catch (DbUpdateConcurrencyException ex)
{
Console.WriteLine("Concurrency Exception Occurred.");
}
}
Console.WriteLine("*** OptimisticConcurrency Ends ***");
}
private static void AddStudents(string[] studentNames)
{
using (var context = new SchoolDBEntities())
{
foreach (var member in studentNames)
{
var newStudent = context.Students.Add(
new Student()
{
StudentName = member
}
);
context.SaveChanges(); // Executes Insert command
}
}
}
public static void SpatialDataType()
{
Console.WriteLine("*** SpatialDataType Starts ***");
using (var context = new SchoolDBEntities())
{
context.Database.Log = Console.Write;
//Add Location using System.Data.Entity.Spatial.DbGeography
context.Courses.Add(new Course()
{
CourseName = "New Course from SpatialDataTypeDemo", Location = DbGeography.FromText("POINT(-122.360 47.656)")
});
context.SaveChanges();
}
Console.WriteLine("*** SpatialDataTypeDemo Ends ***");
}
static void Main(string[] args)
{
using (var context = new SchoolDBEntities())
{
var studentList = context.Students.ToList <Student>();
//Perform create operation
//context.Students.Add(new Student() { StudentName = "New Student" });
//Perform Update operation
//Student studentToUpdate = studentList.Where(s => s.StudentName == "New Student").FirstOrDefault<Student>();
//studentToUpdate.StudentName = "Edited student1";
////Perform delete operation
context.Students.Remove(studentList.ElementAt <Student>(0));
//Execute Inser, Update & Delete queries in the database
context.SaveChanges();
}
}
static void Main(string[] args)
{
using (var context = new SchoolDBEntities())
{
// Insert
//var std = new Student()
//{
// StudentName = "Jagadish"
//};
// Update
//var std = context.Students.Where(x => x.StudentID.Equals(14)).FirstOrDefault();
//std.StudentName = "Vijay";
// Delete
//var std = context.Students.Where(x => x.StudentID.Equals(15)).FirstOrDefault();
//context.Students.Remove(std);
int statuscount = context.SaveChanges();
if (statuscount > 0)
{
Console.WriteLine("Record Updated Successfully");
}
else
{
Console.WriteLine("Insert Record Failed");
}
// Fetch data from the database
//Querying with LINQ to Entities
//var query = context.Students
// .Where(s => s.StudentName == "Bill")
// .FirstOrDefault<Student>();
//Console.WriteLine(query.StudentID + query.StudentName );
////Querying with Object Services and Entity SQL
//string sqlString = "SELECT VALUE st FROM SchoolDBEntities.Students " +
// "AS st WHERE st.StudentName == 'Bill'";
//var objctx = (context as IObjectContextAdapter).ObjectContext;
//ObjectQuery<Student> student = objctx.CreateQuery<Student>(sqlString);
//Student newStudent = student.First<Student>();
//var anonymousResult = from s in context.Students
// where s.StandardId == 1
// select new
// {
// ID = s.StandardId,
// Name = s.StudentName
// };
//foreach(var obj in anonymousResult)
//{
// Console.WriteLine("ID: " + obj.ID + " Name: " + obj.Name);
//}
//var MethodSyntax = context.Students
// .Where(x => x.StandardId == 1)
// .Select(x =>
// new
// {
// StudentID = x.StudentID,
// StudentName = x.StudentName
// });
//foreach (var obj in MethodSyntax)
//{
// Console.WriteLine("StudentID: " + obj.StudentID + " StudentName: " + obj.StudentName);
//}
//var stud1 = (from s in context.Students.Include("Standard")
// where s.StudentName == "Bill"
// select s).FirstOrDefault<Student>();
//Console.WriteLine("ID: " + stud1.StudentID + " Name: " + stud1.StudentName + " "+ stud1.Standard.Description);
//// disconnected new entity
//var studentNew = new Student() { StudentName = "Bill", StandardId =2 };
//context.Entry(studentNew).State = studentNew.StudentID == 0 ? EntityState.Added : EntityState.Modified;
//context.SaveChanges();
//foreach (var entity in context.ChangeTracker.Entries())
//{
// Console.WriteLine("{0}: {1}", entity.Entity.GetType().Name, entity.State);
//}
Console.ReadLine();
}
Console.WriteLine("Hello");
}
