如何在Foreach循环中更新IList中的记录？

Question

My controller is passing through a list which I then need to loop through and update every record in the list in my database. I'm using ASP.NET MVC with a repository pattern using Linq to Sql. The code below is my save method which needs to add a record to an invoice table and then update the applicable jobs in the job table from the db.

public void SaveInvoice(Invoice invoice,  IList<InvoiceJob> invoiceJobs)
{
    invoiceTable.InsertOnSubmit(invoice);
    invoiceTable.Context.SubmitChanges();

    foreach (InvoiceJob j in invoiceJobs)
    {
        var jobUpdate = invoiceJobTable.Where(x => x.JobID == j.JobID).Single();
        jobUpdate.InvoiceRef = invoice.InvoiceID.ToString();
        invoiceJobTable.GetOriginalEntityState(jobUpdate);
        invoiceJobTable.Context.Refresh(RefreshMode.KeepCurrentValues, jobUpdate);
        invoiceJobTable.Context.SubmitChanges();
    }
}

**I've stripped the code down to just the problem area.

This code doesn't work and no job records are updated, but the invoice table is updated fine. No errors are thrown and the invoiceJobs IList is definitely not null. If I change the code by removing the foreach loop and manually specifying which JobId to update, it works fine. The below works:

public void SaveInvoice(Invoice invoice,  IList<InvoiceJob> invoiceJobs)
{
    invoiceTable.InsertOnSubmit(invoice);
    invoiceTable.Context.SubmitChanges();

    var jobUpdate = invoiceJobTable.Where(x => x.JobID == 10000).Single();
    jobUpdate.InvoiceRef = invoice.InvoiceID.ToString();
    invoiceJobTable.GetOriginalEntityState(jobUpdate);
    invoiceJobTable.Context.Refresh(RefreshMode.KeepCurrentValues, jobUpdate);
    invoiceJobTable.Context.SubmitChanges();
}

I just can't get the foreach loop to work at all. Does anyone have any idea what I'm doing wrong here?

Answer 1

It seems like the mostly likely cause of this problem is that the invokeJobs collection is an empty collection. That is it has no elements hence the foreach loop effectively does nothing.

You can verify this by adding the following to the top of the method (just for debugging purposes)

if (invoiceJobs.Count == 0) {
  throw new ArgumentException("It's an empty list");
}

Answer 2

Change this

        var jobUpdate = invoiceJobTable.Where(x => x.JobID == 10000).Single();
        jobUpdate.InvoiceRef = invoice.InvoiceID.ToString();
        invoiceJobTable.GetOriginalEntityState(jobUpdate);
        invoiceJobTable.Context.Refresh(RefreshMode.KeepCurrentValues, jobUpdate);
        invoiceJobTable.Context.SubmitChanges();

to

        var jobUpdate = invoiceJobTable.Where(x => x.JobID == 10000).Single();
        jobUpdate.InvoiceRef = invoice.InvoiceID.ToString();
        invoiceJobTable.SubmitChanges();

It looks like your GetOriginalEntityState doesn't actually do anything, because you don't use the returned value. I can't see any reason why you are making the DataContext.Refresh() call. All it does is erase the changes you made, thus making your "foreach loop not work"