Question

I’ve got a number of classes which have a relationship to other classes for properties like Location, Currency etc. Take the following example:

Public Class Transaction
     Public Property ID As Integer
     Public Property Description As String
     Public Property Quantity As Integer
     Public Property SaleAmount As Double
     Public Overridable Property Currency As Currency
 End Class

 Public Class Currency
     Public Property ID As String
     Public Property Description As String
     Public Property Symbol As String
     Public Property SymbolImage As String
 End Class

I add my currencies when I initialise the application for first use. When adding a transaction, I have a drop down box to select the currency.
I have no issues saving the Transaction to the db and the currency ID is saved also.

When I edit the transaction and try to change the currency, I can’t get it to save back to the db.

 <HttpPost()>
    Function Edit(transaction As Transaction) As ActionResult
        transaction.Currency = db.Currencies.Find(transaction.Currency.ID)
        Debug.Print("Currency: " & transaction.Currency.ID)
        If ModelState.IsValid Then
            db.Entry(transaction).State = EntityState.Modified
            db.SaveChanges()
            Return RedirectToAction("Index")
        End If

        Return View(transaction)
    End Function

When I do the debug.print in the post method above, the currency is correctly being reported as the changed currency but the Currency ID on the Transaction record in the DB isn’t updated.

I’ve done some searching and reading and haven’t found much/anything.
I did try adding this line to the post method but it still didn’t save the changes:

db.Entry(transaction.Currency).State = EntityState.Modified

I’m stumped and would appreciate any help!

Answer 1

So here’s the best solution I could find. I’d be interested to hear other ways to achieve the same result. The other methods I’ve found are much more complicated than this.

Public Class Transaction
    Public Property ID As Integer
    Public Property Description As String
    Public Property Quantity As Integer
    Public Property SaleAmount As Double
    Public Property Name As String

    Public Property CurrencyID() As String
    <ForeignKey("CurrencyID")>
    Public Overridable Property Currency() As Currency
End Class

I’ve setup the Edit view with a drop down list containing a list of the currencies and a hidden field to store the CurrencyID. The edit post looks like this:

<HttpPost()>
Function Edit(transaction As Transaction) As ActionResult
    If ModelState.IsValid Then
        db.Entry(transaction).State = EntityState.Modified
        db.SaveChanges()
        Return RedirectToAction("Index")
    End If

    Return View(transaction)
End Function