Question

Let’s say we have a code list of all the countries including their country codes. The country code is primary key of the Countries table and it is used as a foreign key in many places in the database. In my application the countries are usually displayed as dropdowns on multiple forms.

Some of the countries, that used to exists in the past, don’t exist any more, for example Serbia and Montenegro, which had the country code of SCG.

I have two objectives:

• don’t allow the user to use these old values (so these values should not be visible in dropdowns when inserting data)
• the user should still be able to (readonly) open old stuff and in this case the deprecated values should be visible in dropdowns.

I see two options:

• Rename deprecated values, for instance from ‘CountryName’ to ‘!!!!!CountryName’. This approach is the easiest to implement, but with obvious drawbacks.
• Add IsActive column to Countries table and set it to false for all deprecated values and true for all other. On all the forms where the user can insert data, display only values which are active. On the readonly forms we can display all values (including deprecated ones) so the user will be able to display old data. But on some of my forms the user should be able to also edit data, which means that the deprecated values should be hidden from him. That means, that each dropbox should have some initialization logic like this: if the data displayed is readonly, then include deprecated values in dropbox and if the data is for edit also, then exclude them. But this is a lot of work and error prone too.

And other ideas?

Answer 1

I deal with this scenario a lot, and use the ‘Active’ flag to solve the problem, much as you described. When I populate a drop-down list with values, I only load ‘active’ data and include upto 1 deprecated value, but only if it is being used. (i.e. if I am looking at a person record, and that person has a deprecated country, then that country would be included in the Drop-downlist along with the active countries. I do this in read-only AND in edit modes, because in my cases, if a person record (for example) has a deprecated country listed, they can continue to use it, but once they change it to a non-deprecated country, and then save it, they can never switch back (your use case may vary).

So the key differences is, even in read-only mode I don’t add all the deprecated countries to the DDL, just the deprecated country that applies to the record I am looking at, and even then, it is only if that record was already in use.

Here is an example of the logic I use when loading the drop down list:

    protected void LoadSourceDropdownList(bool AddingNewRecord, int ExistingCode)
    {
        using (Entities db = new Entities())
        {
            if (AddingNewRecord) // when we are adding a new record, only show 'active' items in the drop-downlist.
                ddlSource.DataSource = (from q in db.zLeadSources where (q.Active == true) select q);

            else // for existing records, show all active items AND the current value.
                ddlSource.DataSource = (from q in db.zLeadSources where ((q.Active == true) || (q.Code == ExistingCode)) select q);

            ddlSource.DataValueField = "Code";
            ddlSource.DataTextField = "Description";
            ddlSource.DataBind();

            ddlSource.Items.Insert(0, "--Select--");
            ddlSource.Items[0].Value = "0";
        }
    }