How to update existing rows using Entity Framework? - asp.net-mvc

Question

I have the following one to many table as below. I am experiencing issue when it comes to editing the existing rows with the following code. Please understand that I am pretty new to the ET relationship, so any detailed explanation would be greatly appreciated. Why it is returning null values?
public void UpdateReportGroup(TReportHeaderModel model)
{
if (model.THeaderTitle == null)
{
throw new Exception("Report Group Title must be filled in");
}
if (model.THeaderTitle.Length <= 0)
{
throw new Exception("A Report Group Title must be filled in.");
}
using (var connection = new TReportEntitiesConnection())
{
var header = connection.THeaders.SingleOrDefault(f => f.ID == model.ID);
var reports = connection.TReport.Where(f => f.THeaderID == model.ID);
connection.TReport.RemoveRange(reports);
foreach (var urls in model.TReports)
{
connection.TReport.Add(new TReport()
{
TReportName = urls.name,
URL = urls.url,
});
}
connection.THeaders.Add(header);
connection.SaveChanges()
}
}
Everytime, I debug it,it is giving null values for the 'TReport' table.
My create new rows works perfectly with the following code. Meaning, I am returning the correct form with correct field names.
public void CreateReport(TReportHeaderModel model)
{
if (model.THeaderTitle == null)
{
throw new Exception("Report Group Title must be filled in");
}
if (model.THeaderTitle.Length <= 0)
{
throw new Exception("A Report Group Title must be filled in.");
}
using (var connection = new TReportEntitiesConnection())
{
var header = new THeader()
{
ClientID = model.ClientID,
THeaderTitle = model.THeaderTitle,
RowNumber = model.RowNumber
};
foreach (var urls in model.TReports)
{
header.TReports.Add(new TReport()
{
TReportName = urls.name,
URL = urls.url
});
}
connection.THeaders.Add(header);
connection.SaveChanges();
}
}
As you can see, I am following DI pattern, and therefore I am calling these two methods in my controller as below:
[HttpPost]
public ActionResultModel CreateReportAPI([FromBody] TReportHeaderModel model) //attempt 3
{
try {
if (ModelState.IsValid)
{
var isValid = _tReportingService.HeadernameExists(model.THeaderTitle);
if (!isValid)
{
Console.WriteLine("it does not exist");
var user = this.GetCurrentUserAccount();
model.ClientID = user.SelectedClient.ID;
_tReportingService.CreateReport(model);
}
else //Update method comes till here and it goes //straight to the error
{
Console.WriteLine("it exists");
var user = this.GetCurrentUserAccount();
model.ClientID = user.SelectedClient.ID;
_tReportingService.UpdateReportGroup(model);
}
}
return new ActionResultModel()
{
Success=true,
Message="Report Group Successfully Saved."
};
}

Answer 1

I guess it would be the last time I'd posting questions here as I understood that it takes you nowhere if you just ask so I'd rather research more and keep trying it until I got it so here I am answering my own question as I'd solved it.
As the model gets generated from WebApi which is completely detached from ET, I am loading the database first and compare which children have been added, deleted & updated. Here is an example of perfect one to many relationship's update/delete.
using (var connection = new TReportEntitiesConnection())
{
var header = connection.THeaders.Include("TReports").SingleOrDefault(f => f.ID == model.ID);
if (header != null)
{
header.THeaderTitle = model.THeaderTitle; //update parent
}
foreach (var existingChild in header.TReports.ToList())
{
if (!model.TReports.Any(c => c.ID == existingChild.ID))
connection.TReport.Remove(existingChild);
}
foreach (var url in model.TReports)
{
var existingChild = header.TReports
.Where(c => c.ID == url.ID)
.SingleOrDefault();
if (existingChild != null)
{ //update child
connection.Entry(existingChild).CurrentValues.SetValues(url);
}
else
{
var newChild = new TReport
{
TReportName = url.name,
URL = url.url,
};
header.TReports.Add(newChild);
}
}
connection.SaveChanges();
}