Updating one column when a row has changes, DMS 1.2.0

[NancyFolsom]

When a row on the client has changed, I have a LastUpdated timestamp that I need to update on the server. I'm close, but it's failing for some reason. In this case I have one row on the client with one change.

The RemoteOrchestrator.OnTableChangesApplying executes twice, which I don't understand. It's the second time that throws an exception.

Here's my code:

CancellationToken cancellationToken = new CancellationToken();

 var syncSetup = new SyncSetup(Tables);

 var remoteProvider = new SqlSyncChangeTrackingProvider(ServerConnectionString);
 var clientProvider = new SqlSyncChangeTrackingProvider(ClientConnectionString);

 var agent = new SyncAgent(clientProvider, remoteProvider);

 agent.RemoteOrchestrator.OnTableChangesApplying(args =>
 {
     if (args.BatchPartInfos != null) // Called twice
     {
         if (args.SchemaTable.TableName != "Inspection")
             return;
         var syncTable = agent.RemoteOrchestrator.LoadTableFromBatchInfo(
                                   args.BatchInfo, args.SchemaTable.TableName, args.SchemaTable.SchemaName, args.State);

         if (syncTable.HasRows) // HasRows is false the second time it's called
         {
             foreach (var row in syncTable.Rows)
             {
                 if (row.RowState != SyncRowState.Modified)
                     continue;
                 row["LastUpdated"] = DateTime.UtcNow;
             }
         }
     }
 });

 var si = await agent.SynchronizeAsync(SyncOptions.DefaultScopeName, syncSetup, syncType, null, progress,
     cancellationToken).ConfigureAwait(false);

The exception on the second loop call is

Index was outside the bounds of the array.  Exception Attributes:
    Message: Index was outside the bounds of the array.
    Exception type: System.IndexOutOfRangeException
    Source: Dotmim.Sync.Core
    Thrown by code in method: CreateSyncRowFromReader
    Thrown by code in class: BaseOrchestrator

I'm suspecting maybe that the problem that it's changed mid transaction or that I'm changing it on the server, but not on the client? But I'm not sure how to do this.

Any suggestions would be very welcome. TIA.

[Mimetis]

Are you able to provide a small repro sample, that I can use to reproduce the error ?

By the way, OnTableChangesApplying is called twice because of the row state:

• 1st call for all rows that are in state Modified (added or updated rows)
• 2nd call for all rows that are in state Deleted

So, the two call are normals.

The difference is that the second call contains only rows with only the primary key.
If you have some deleted rows, the row["LastUpdated"] is not existing.

Anyway, even if it's working, your scenario will not eventually.
In your case, you are loading all the rows from the batch, but once you're done with the modification, it's not saved anywhere.

If you really want to add this LastUpdated value, your best chance is to use the OnRowsChangesApplying interceptor.

the OnRowsChangesApplying is the only one that is raised when rows are in memory, ready to be applied.

Here a small piece of code I used to test with AdventureWorks:

agent.RemoteOrchestrator.OnRowsChangesApplying(args =>
{
    if (args.SchemaTable.TableName != "ProductCategory")
        return;

    if (args.SyncRows.Count > 0)
    {
        foreach (var row in args.SyncRows)
        {
            if (row.RowState != SyncRowState.Modified)
                continue;

            row["ModifiedDate"] = DateTime.UtcNow;
        }
    }
});

[NancyFolsom]

Thank you for the quick reply and suggestion. Creating an example that has the same problem is probably not practical. If it's working for you with AdventureWorks, I definitely think the problem is in my code or database setup.

Yes, I am sure I want to do this. I need to do this, in fact. I have two goals right now: 1. update DMS (I was on 0.8); and 2. specifically update DMS so I can change the value of a column during sync for rows that have changes in the local db.

I tried OnRowsChangesApplying using your example, but I have the same problem (using my architecture and database).

Same exception: "Index was outside the bounds of the array."

Is it a problem that I'm changing the row on the RemoteOrchestrator but not doing something with the LocalOrchestrator? The detail of the call stack references the LocalOrchestrator. In other words, has the local db been updated from the server, but now I'm updating server data that is not local?

In case I didn't say and it matters: this is a .Net Standard WPF app.

[Mimetis]

No idea, honestly.
Need a sample repro to help you figure it out

[NancyFolsom]

Okay. I'll try to build a sample that duplicates the problem, which is an entirely reasonable request. :-) Thanks for your time.

[NancyFolsom]

I got it working! The problem was, I think, that I was changing the backend from SSMS in order to test my changes, and it seemed to confuse the change tracking. Which seems obvious in hindsight. Thanks for taking a look. I appreciate DMS so much. It's a wonderful tool.