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Auto increment column for specific Id in some table related to anther table C# mvc

I have a table named Payment which has a column named IndexOrder and all I need when I add a new payment, the AddEdit function will check first if there is any value in IndexOrder Column for this specific Id then increment Indexorder with 1 and so on for every new PaymentId. my AddEdit function code is like:
[HttpPost]
public ActionResult AddEdit(PaymentModel model )
{
if (ModelState.IsValid)
{
var userId = User.Identity.GetUserId();
Payment obj = context.Payment
.Where(p => p.Id == model.Id).FirstOrDefault();
if (obj == null)
{
obj = new Payment();
if (model.File != null)
{
Guid nme = Guid.NewGuid();
string filename = nme + Path.GetExtension(model.File.FileName);
string filepath = Path.Combine(Server.MapPath("/FilesUpload/") + filename);
model.File.SaveAs(filepath);
obj.Path = filename;
}
Mapper.FillObjectFromModel(obj, model);
obj.CreatedBy = userId;
obj.ModifiedBy = userId;
obj.CreatedAt = DateTime.Now;
obj.ModifiedAt = DateTime.Now;
context.Payment.Add(obj);
context.SaveChanges();

So did i get that right? For every new payment that relates to a specific id (assuming a product or something) you want aincremented IndexOrder?
I would not use an IndexOrder column for that but instead just order by timestamp. Assuming you need that for kind of transactionhistory just read them payments like
context.Payments.Where(x => x.ProductId == myProductId).OrderBy(x => x.timestamp);
But to answer your question this should be quite simple, e.g:
var nextIndex = context.Payments.Where(x => x.ProductId == myProductId).Count +1;

Null on updated fields

I am trying to update one single field in a table but it's giving me an error saying that the other content is null. I'm trying to update one single field from a table and leave the other fields as they were.
Code so far:
var user = new User() { CardNumber = cardNumber };
using (var db = new Entities())
{
db.Users.Attach(user);
db.Entry(user).Property(x => x.CardNumber).IsModified = true;
db.Configuration.ValidateOnSaveEnabled = false;
db.SaveChanges();
}

Here is a code example to update the card number and save it.
using (var db = new Entities())
{
User user = db.Users.Where(u => u.Id == userIdToBeUpdated).FirstOrDefault();
user.CardNumber = cardNumber;
db.SaveChanges();
}

Enter new data in db (EF)

I have method in controller
It receive data from post request and write to table
Here is code
[ResponseType(typeof(TimeTable))]
public IHttpActionResult PostTimeTable(TimeTable timeTable)
{
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
if (ModelState.IsValid)
{
DateTime dt = DateTime.Today;
TimeTable c = (from x in db.TimeTables
where x.Company == timeTable.Company && x.INN == timeTable.INN
select x).First();
c.StartPause = timeTable.StartPause;
c.StartDay = timeTable.StartDay;
c.EndPause = timeTable.EndPause;
c.EndDay = timeTable.EndDay;
db.SaveChanges();
}
db.TimeTables.Add(timeTable);
db.SaveChanges();
return CreatedAtRoute("DefaultApi", new { id = timeTable.Id }, timeTable);
}
But it works well when record with INN and Company already in db.
But if it not in database I need to create new entry.
How I need to modify this method?

You can use a flag (exisingCompanyFlag) for edit mode or add new mode like this
bool existingCompanyFlag = true;
TimeTable c = (from x in db.TimeTables
where x.Company == timeTable.Company && x.INN == timeTable.INN
select x).FirstOrDefult();
if (c == null)
{
existingCompanyFlag = false;
c = new TimeTable();
}
c.StartPause = timeTable.StartPause;
c.StartDay = timeTable.StartDay;
c.EndPause = timeTable.EndPause;
c.EndDay = timeTable.EndDay;
if (!existingCompanyFlag)
db.TimeTables.Add(c);

You need a separate branch in your code for the insert case.
if (ModelState.IsValid) {
if (addingNewRow) {
TimeTable tt = new TimeTable {
// Populate properties (except identity columns)
};
db.TimeTables.Add(tt);
} else {
// update
}
db.SaveChanges();
}
To link to other entities use one of:
Assign instances:
x.Company = theCompany;
or, assign the instance id
x.CompanyId = companyId;
(#1 is easier if you already have the other entity loaded or are creating it – EF will sort out the ids – while #2 saves loading the whole other entity.)

C# Create employee. Save to SQL Database using EF

I'm saving an employee to a SQL database. I'm saving Firstname, Lastname, Username and Password. How should I do this to prevent saving more than one identical username?
I've tried this:
private void CreateEmployee()
{
using (var db = new TidrapportDBEntities())
{
var user = (from p
in db.Login
where p.username != null
select p).ToList();
foreach (var vUser in user)
{
if (vUser.username == textBoxUsername.Text)
{
labelSuccessFail.Visible = true;
labelSuccessFail.Text = "Accountname already exist.";
break;
}
else
{
var userInfo = new Login();
var persInfo = new PersonalInformation();
persInfo.firstname = textBoxFirstname.Text;
persInfo.lastname = textBoxLastname.Text;
userInfo.username = textBoxUsername.Text;
userInfo.password = textBoxPassword.Text;
userInfo.employeeId = persInfo.employeeId;
db.Login.Add(userInfo);
db.PersonalInformation.Add(persInfo);
db.SaveChanges();
textBoxFirstname.Text = string.Empty;
textBoxLastname.Text = string.Empty;
textBoxUsername.Text = string.Empty;
textBoxPassword.Text = string.Empty;
labelSuccessFail.Visible = true;
labelSuccessFail.Text = "Successfully created account.";
}
}
}
}
Any tips what I can try?
Kind regards,
Kristian

You should have a unique constraint on the username field. Not sure if you're doing code first, model first or DB first in your EF, but you should be able to google how to get it set on your database using the right method. That will throw an exception if you try to save one, so that makes sure you can't have more than one.
You could also use LINQ statement to restrict the list of users to the user name you wish to create and then you're just down to checking a bool to see if a row is returned or not. That way you're not having to read the entire database table (which your "toList" is doing).
In your code example, you're getting all the users where they have a user name, you're then looping round them, but your conditional code only really works if the first one matches the user name you're trying to save, otherwise you are going to try and recreate a duplicate the second time around. So just to get your code working you could try:
private void CreateEmployee()
{
using (var db = new TidrapportDBEntities())
{
var user = (from p
in db.Login
where p.username != null
select p).ToList();
bool found = false;
foreach (var vUser in user)
{
if (vUser.username == textBoxUsername.Text)
{
found = true;
labelSuccessFail.Visible = true;
labelSuccessFail.Text = "Accountname already exist.";
break;
}
}
if(!found)
{
var userInfo = new Login();
var persInfo = new PersonalInformation();
persInfo.firstname = textBoxFirstname.Text;
persInfo.lastname = textBoxLastname.Text;
userInfo.username = textBoxUsername.Text;
userInfo.password = textBoxPassword.Text;
userInfo.employeeId = persInfo.employeeId;
db.Login.Add(userInfo);
db.PersonalInformation.Add(persInfo);
db.SaveChanges();

Insert data using Entity Framework model

I'm trying to insert some data in my database using Entity Framework model, but for some unknown reasons to me, it does nothing.
Am I missing something here?
using (var context = new DatabaseEntities())
{
var t = new test
{
ID = Guid.NewGuid(),
name = "blah",
};
context.AddTotest(t);
context.SaveChanges();
}

It should be:
context.TableName.Add(TableEntityInstance);
For versions of entity framework before 6, it was:
context.TableName.AddObject(TableEntityInstance);
Where:
TableName: the name of the table in the database.
TableEntityInstance: an instance of the table entity class.
If your table is Orders, then:
Order order = new Order();
context.Orders.Add(order);
For example:
var id = Guid.NewGuid();
// insert
using (var db = new EfContext("name=EfSample"))
{
var customers = db.Set<Customer>();
customers.Add( new Customer { CustomerId = id, Name = "John Doe" } );
db.SaveChanges();
}
Here is an example:
public void UpdatePlayerScreen(byte[] imageBytes, string installationKey)
{
var player = (from p in this.ObjectContext.Players where p.InstallationKey == installationKey select p).FirstOrDefault();
var current = (from d in this.ObjectContext.Screenshots where d.PlayerID == player.ID select d).FirstOrDefault();
if (current != null)
{
current.Screen = imageBytes;
current.Refreshed = DateTime.Now;
this.ObjectContext.SaveChanges();
}
else
{
Screenshot screenshot = new Screenshot();
screenshot.ID = Guid.NewGuid();
screenshot.Interval = 1000;
screenshot.IsTurnedOn = true;
screenshot.PlayerID = player.ID;
screenshot.Refreshed = DateTime.Now;
screenshot.Screen = imageBytes;
this.ObjectContext.Screenshots.Add(screenshot);
this.ObjectContext.SaveChanges();
}
}

var context = new DatabaseEntities();
var t = new test //Make sure you have a table called test in DB
{
ID = Guid.NewGuid(),
name = "blah",
};
context.test.Add(t);
context.SaveChanges();
Should do it

[HttpPost] // it use when you write logic on button click event
public ActionResult DemoInsert(EmployeeModel emp)
{
Employee emptbl = new Employee(); // make object of table
emptbl.EmpName = emp.EmpName;
emptbl.EmpAddress = emp.EmpAddress; // add if any field you want insert
dbc.Employees.Add(emptbl); // pass the table object
dbc.SaveChanges();
return View();
}