ADO.NET更新不起作用

Question

Could one of you lovely people shed some light as to why this code doesn't work or a better/correct way of performing it...

CandidDomainService db = new CandidDomainService();

GlobalValuesTable newInstanceId =
    db.GetGlobalValuesTables().Single<GlobalValuesTable>(gId => gId.RowId == 1);

newInstanceId.CurrentTestInstance++;
db.UpdateGlobalValuesTable(newInstanceId);

It's throwing a null exception at db.Update . I'm using the generated add, update, remove and get. The exception is described as being thrown when no changes have been made to the entity model.

Thanks!

EDIT:

This is the update code generated...

    public void UpdateGlobalValuesTable(GlobalValuesTable currentGlobalValuesTable)
    {
        this.ObjectContext.GlobalValuesTables.AttachAsModified(currentGlobalValuesTable, 
            this.ChangeSet.GetOriginal(currentGlobalValuesTable));
    }

And it is THIS that is throwing the error, what's more it does not actually update. I also tried this code in place of it...

    public void UpdateGlobalValuesTable(GlobalValuesTable d)
    {
        var newInstanceId =
            this.ObjectContext.GlobalValuesTables.Single<GlobalValuesTable>
                (gId => gId.RowId == 1);

        // Update the current instance ID
        newInstanceId.CurrentTestInstance++;

        this.ObjectContext.AcceptAllChanges();

      //this.ObjectContext.GlobalValuesTables.Context.AcceptAllChanges();
      //this.ObjectContext.GlobalValuesTables.Context.AttachAsModified(newInstanceId);
    }

Answer 1

As with most things, I would check that it exists before calling it.

if (newInstanceId)
{
newInstanceId.CurrentTest Instance++;
db.UpdateGlobalValuesTable(newInstanceId);
}
else 
{
//Do something here to notify you.
}

That should at least get you into some better debugging.