/// <summary>
/// Updates the one singer by identifier.
/// </summary>
/// <returns>Return the error code</returns>
/// <param name="id">Identifier.</param>
/// <param name="singer">Singer.</param>
public async Task <int> UpdateOneSingerById(int id, Singer singer)
{
int result = ErrorCodeModel.ErrorBecauseBugs;
if (id == 0)
{
// its a bug, id of singer cannot be 0
result = ErrorCodeModel.ErrorBecauseBugs;
return(result);
}
if (singer == null)
{
// the data for updating is empty
result = ErrorCodeModel.SingerIsNull;
return(result);
}
if (string.IsNullOrEmpty(singer.SingNo))
{
// the singer no that input by user is empty
result = ErrorCodeModel.SingerNoIsEmpty;
return(result);
}
Singer newSinger = await FindOneSingerBySingNo(singer.SingNo);
if (newSinger != null)
{
if (newSinger.Id != id)
{
// singer no is duplicate
result = ErrorCodeModel.SingerNoDuplicate;
return(result);
}
}
Singer orgSinger = await FindOneSingerById(id);
if (orgSinger == null)
{
// the original singer does not exist any more
result = ErrorCodeModel.OriginalSingerNotExist;
return(result);
}
else
{
orgSinger.CopyColumnsFrom(singer);
// verifying the validation for Singer data
int validCode = await VerifySinger(orgSinger);
if (validCode != ErrorCodeModel.Succeeded)
{
// data is invalid
result = validCode;
return(result);
}
// check if entry state changed
if ((_context.Entry(orgSinger).State) == EntityState.Modified)
{
using (var dbTransaction = _context.Database.BeginTransaction())
{
try
{
await _context.SaveChangesAsync();
dbTransaction.Commit();
result = ErrorCodeModel.Succeeded; // succeeded to update
}
catch (DbUpdateException ex)
{
string msg = ex.ToString();
Console.WriteLine("Failed to update singer table: \n" + msg);
dbTransaction.Rollback();
result = ErrorCodeModel.DatabaseError;
}
}
}
else
{
result = ErrorCodeModel.SingerNotChanged; // no changed
}
}
return(result);
}
