Question

I’m newbie to Visual Studio 2010 .NET 4.0 Dynamic Data. Now I’m trying to do a simple dropdown list for my Web site (written in C#).

I’ve got a field called protocol (as in TCP-protocol). I want the user to be able to choose one of static values.
In olden days with classic ASP and HTML I would have used something like this:

<form name=form1 method="POST" action="./insert.asp">
...
     <select name="PROTOCOL" size="1">
        <option value="https" selected>https
        <option value="sftp">sftp
        <option value="ftps">ftps
     </SELECT>
...
</form>

… and then handled the database in the ./insert.asp.

So far I’ve found instruction on how to do this in Visual Studio 2008 (.NET 3.5), but this doesn’t work in WS2010 and .NET 4.0:
http://csharpbits.notaclue.net/2008/07/dynamic-data-and-field-templates-your.html

Following the instructions in http://www.asp.net/web-forms/videos/aspnet-dynamic-data I’ve figured that in order to customize my fields I need to

• Create file for my custom code in the App_Code folder (MyService.cs).
• Create a ‘public partial class’ for my MS-SQL -table (service).

Here’s my (¿pathetic?) effort (App_Code/MyService.cs):

// MyService.cs
using System;
using System.ComponentModel.DataAnnotations;
using System.Web;
using System.ComponentModel;

   [MetadataType(typeof(serviceMetadata))]
    public partial class service
    {

    }

    public class serviceMetadata
    {
        [EnumDataType(typeof(ProtocolType))]
        public object protocol { get; set; }

    }

   public enum ProtocolType
    {
        https,
        sftp,
        ftps
    }

This builds ok, but running it ends with “ArgumentException was unhandled by user code / The value passed in must be an enum base or an underlying type for an enum, such as an Int32.” message in \DynamicData\FieldTemplates\Enumeration.ascx.cs -file.

Help appreciated.

Answer 1

OK, since nobody has tried to answer this, I’ll try to answer my own question.

Seems to me that there is not out-of-the-box method for this problem. However, in my mind (please do correct me if I’m wrong) there are three possible solutions for this problem:

1. Change the database structure
   • Add new table, which contains the protocols and link it to service table:
     • Add a protocols -table containing these fields.
       • protocols.id (int, Primary Key)
       • protocols.protocol (char(10))
   • Delete (drop) the service.protocol -field
   • Add a service.protocols_id -field.
   • Make relation: FK:service.protocols_id –references–>> PK:protocols.id

2. Change the service.protocol -field to numeric (int)

   • Replace the protocol names with numeric values (1, 2, 3)

   • Change the enum -code:

     public enum ProtocolType 
     {
         https = 1,
         sftp = 2,
         ftps = 3
     }
     

   • More on the subject: http://msdn.microsoft.com/en-us/library/system.componentmodel.dataannotations.enumdatatypeattribute.aspx

3. Create your own FieldTemplate

   • Requires in-depth knowledge on .NET 4.0, DynamicData, C# (or whatever your programming language is), data context (=classes to represent database entities)
   • You can get started by right-clicking the …\DynamicData\FieldTemplates\ -folder, choose DynamicDataField, rename as MyDropDownList, click Add.
   • More on the subject: http://msdn.microsoft.com/en-us/library/cc488522.aspx

Comments are welcome.