Dfyjkt

I need to load records from an existing database into a new database using a LINQ query using LINQPad. If the record exists in the database, then update the name. Otherwise, insert the record. Currently, the new DB is empty. This script will run periodically, so I have to check for updates. I have code that loads the existing and new records into two List for comparison. I loop through the list:

foreach (Coaster oldCoaster in listOfOldCoasters) 
 var coaster = listOfNewCoasters.Where(c => c.coasterId == oldCoaster.coasterId).FirstOrDefault();

 if (coaster != null) 
 coaster.Name = oldCoaster.Name;
 else 
 coaster = new Models.Coaster();
 coaster.CoasterId = oldCoaster.coasterId;
 coaster.Name = oldCoaster.Name;
 //newCoasterDbContext.Coasters.Attach(coaster);
 newCoasterDbContext.Coasters.Add(coaster);
 


newCoasterDbContext.SaveChanges();

When I run the code using the "Add" method, I receive the exception "OriginalValues cannot be used for entities in the Added state." Digging deeper, I see this message:

Cannot insert the value NULL into column 'CoasterId', table 'Coaster'; column does not allow nulls. 

I am setting the primary key in question, so I must be missing something about EF as to why this fails. If I uncomment the "Attach" statement and try that instead of "Add", then the script runs, but nothing gets inserted into the database.

My Coaster class:

public class Coaster

 public System.Guid CoasterId get; set; 
 public string Name get; set; 

 public Coaster()
 
 CoasterId = System.Guid.NewGuid();
 

Based on other posts, I have tried adding attributes to the PK:

 [Key]
 [DatabaseGenerated(DatabaseGeneratedOption.None)]

And I have tried modifying the OnModelCreating method:

HasKey(x => x.CoasterId).Property(x => x.CoasterId).HasDatabaseGeneratedOption(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.None);

These haven't worked for me. What have I missed that is causing Entity Framework to ignore the GUID that I have attached to the primary key field?

You can't fix stupid, but you can fix stupid mistakes. So as I mentioned, in the OnModelCreating method, I had this line:

HasKey(x => x.CoasterId).Property(x => x.CoasterId).HasDatabaseGeneratedOption(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.None);

I thought it didn't work, but that was only because a bit later in the method, there was a line that overwrote change:

Property(x => x.FpoDistrictId).HasColumnName(@"FPODistrictId").HasColumnType("uniqueidentifier").IsRequired().HasDatabaseGeneratedOption(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity);

At least I figured it out...