public UpdateRegionPage(Reggion region)
{
InitializeComponent();
var viewModel = new UpdateRegionViewModel();
viewModel.Region = region;
BindingContext = viewModel;
}
public async Task <UpdateRegionViewModel> Update(Region region)
{
var updateViewModel = new UpdateRegionViewModel();
var regionUpdate = await GetDbSet <Region>().FirstOrDefaultAsync(x => x.RegionId == region.RegionId);
try
{
if (regionUpdate != null)
{
// Update the RowVersion to the value when this entity was
// fetched. If the entity has been updated after it was
// fetched, RowVersion won't match the DB RowVersion and
// a DbUpdateConcurrencyException is thrown.
// A second postback will make them match, unless a new
// concurrency issue happens.
Context.Entry(regionUpdate).Property(Constants.Region.RowVersion).OriginalValue = region.RowVersion;
regionUpdate.RegionName = region.RegionName;
regionUpdate.RegionCode = region.RegionCode;
regionUpdate.RegionKey = region.RegionKey;
regionUpdate.Description = region.Description;
}
await UnitOfWork.SaveChangesAsync();
}
catch (DbUpdateConcurrencyException ex)
{
var exceptionEntry = ex.Entries.Single();
var clientValues = (Region)exceptionEntry.Entity;
var databaseEntry = exceptionEntry.GetDatabaseValues();
if (databaseEntry == null)
{
updateViewModel.ValidationResults.Add(new ValidationResult("Unable to save changes. The region was deleted by another user."));
}
else
{
var databaseValues = (Region)databaseEntry.ToObject();
//get all properties of the class(Region)
var properties = databaseValues.GetType().GetProperties();
//iterate class properties and add to validation result list
updateViewModel.ValidationResults.AddRange(from prop in properties
where prop.Name != Constants.Region.RegionId && prop.Name != Constants.Region.RowVersion //exclude Id and RowVersion from the iteration
let dbValue = prop.GetValue(databaseValues) //get database value
let currentValue = prop.GetValue(clientValues) //get current value
where !dbValue.Equals(currentValue) //check if db and current value is not equal
let displayName = prop.GetCustomAttributes(typeof(DisplayAttribute), false) //get display name of property
.Cast <DisplayAttribute>()
.Single()
.Name
select new ValidationResult($"{displayName} current value: {prop.GetValue(databaseValues)}")); //add error to validation result
updateViewModel.ValidationResults.Add(new ValidationResult(@"The record you attempted to edit was modified by another user after you got the original value.
The edit operation was canceled and the current values in the database have been displayed. If you still want to edit this record,
click the Save button again."));
// Save the current RowVersion so next postback
// matches unless a new concurrency issue happens.
if (regionUpdate != null)
{
regionUpdate.RowVersion = updateViewModel.RowVersion = databaseValues.RowVersion;
}
}
}
return(updateViewModel);
}
