Missing data annotation for ForeignKey

Question

User539648229 posted

Hi

I'm trying to use a foreign key with an EntityTemplate. In the none EntityTemplate version that is generated with Webforms Scaffolding tool, a foreign key is used with a DynamicControl with DataTypeName, DataValueField, DataTextField and UIHint attributes and it works fine. It seems that I must provide these data(with some annotation) in my model(code first) to be used with EntityTemplate. Now without providing these data there is the exception "'CalendarId' is not a foreign key column and cannot be used here." in ForeignKey_Edit.ascx. What annotation should I use?

Thanks

Answer 1

User-330204900 posted

Hi IranianCurio, you don't need any more that the field name if you are uysing the Entity framework then you can easily see the foreign key field in the navigation properties of the entity you use that name in the  DataField property and then set the mode using the mode property like below

<asp:DynamicControl ID="DynamicControl1" runat="server" DataField="Type" Mode="Edit" />

the Fk Fiuedl would notmaly be called TypeId in my naming convention but the ForeignKey field would be named after the FK table in this case Type.

Hope that helps.

Answer 2

User539648229 posted

Hi

I guess you mean that I use navigation property(Calendar) instead of FK(CalendarId). At first I used "Calendar" but it didn't work and no control was appeared for Calendar and a Textbox appeared for CalendarId. The reason was that Table.GetScaffoldColumns() in the Entity template file does not return navigation properties. I compared this behavior with the behavior in the Dynamic Data template and the difference was in FormView1.SetMetaTable() in the Init of the page. I added it and now a DropDownList appears for Calendar and but still a Textbox for CalendarId. Even when I Used [Display(AutoGenerateField = false)] for CalendarId there is no Textbox but the a validation message appears "CalendarId is required". Complex situation! Help please.

Thanks

Answer 3

User1686483761 posted

Hi IranianCurious,

I guess you mean that I use navigation property(Calendar) instead of FK(CalendarId). At first I used "Calendar" but it didn't work and no control was appeared for Calendar and a Textbox appeared for CalendarId. The reason was that Table.GetScaffoldColumns() in the Entity template file does not return navigation properties

In my experience, Templates doesn't use data annotations because classes generated from templates don't need them. EF also don't need them because mapping is defined in XML files not in code. If you need data annotations you must either:

• Modify template to use them (this requires understanding of EF metadata model)
• Don't use templates and use code first instead

Besides, you could refer to the following link to display a navigation property.

http://forums.asp.net/t/1730820.aspx?How+can+i+display+a+navigation+property+in+a+grid+view+control+

Best Regards,

sudo

Answer 4

User539648229 posted

Hi

I think there is a misunderstanding. I don't know what do you mean with templates but I mean Entity Templates. In these templates a Dynamic Control is added for each field and this control renders the appropriate control based on data type of the field and metadata provided for it. Also I use Code First.

Answer 5

User-330204900 posted

Yes that is correct :D you use the navigation property

Answer 6

User-330204900 posted

Hi Sudo10, this is Dynamic Data and it does use Page Field and Entity Templates :)

Answer 7

User539648229 posted

Hi sjnaughton

I didn't exactly get what you mean.

Also:

Happy New Year! I wish you an excellent year for you and your family in 2016.

Answer 8

User-330204900 posted

Hi Ali, what I mean is when you are creating a EntityTemplate it is for a specific entity i.e. the Person entity and if the person entity has a FK relationship with say the Title table using the FK column TitleId to Title.Id you don't specify the FK Column but the Navigation Property

<asp:DynamicControl ID="DynamicControl1" runat="server" DataField="Title" Mode="Edit" />

In my example you specify the Title "Navigation Property" to get the correct field template to display in the EntityTemplate.

Hope this helps, maybe i have not understood what you want to achieve :_

Answer 9

User539648229 posted

Hi

As I said Table.GetScaffoldColumns() in the Entity template file does not return navigation properties. I used FK field plus the following in ForeignKey_Edit for overcome the  error('CalendarId' is not a foreign key column and cannot be used here.):

        protected override void ExtractForeignKey(IDictionary dictionary, string selectedValue)
        {
            if (Column is MetaForeignKeyColumn)
                base.ExtractForeignKey(dictionary, selectedValue);
            else if (Column is MetaColumn && Column.HasAttribute<ForeignKeyAttribute>())
                dictionary.Add(Column.Name, selectedValue);
            else
                throw new NotSupportedException("The column must be 'MetaForeignKeyColumn' or 'MetaColumn' with ForeignKey Attribute.");
        }

It works now. Thanks anyway.

Answer 10

User-330204900 posted

hi Ali, glad you are working but still not sure what you are trying to achieve. If the FK Navigation Property is there in the model and it has not been set to be hidden is some way then

Table.GetScaffoldColumns()

will return it, there must be some other issue.

Answer 11

User539648229 posted

Hi

If you use Web Form Scaffolding tool it uses FK instead of Navigation. I think under the situation I described Table.GetScaffoldColumns() returns FK and not Navigation.

Answer 12

User-330204900 posted

OK so you are using Scaffolding not Dynamic Data then? Ah!