Dynamic Data and Enum-bound fields RSS

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  stevekain

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  20 Points

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  Dynamic Data and Enum-bound fields

  Jan 28, 2008 04:48 PM|LINK

  I've got a table where one of the columns is an integer.  In my Linq To Sql mapping I map this column to a field whose type is an Enum.  When I pull up this table in Dynamic Data the column in question is not displayed at all.  What's up with this?  Is there any way to use an Enum-bound field with Dynamic Data? 

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  stevekain

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  16 Posts

  Re: Dynamic Data and Enum-bound fields

  Jan 28, 2008 07:15 PM|LINK

   

   Well, I couldn't wait so I came up with a solution myself.  Now what I'd like to know is if there is a better way to accomplish this.  To do it my way I did the following:

   

  
  1. Open your .dbml file and click on the integer field that should be represented in .NET by an enum type.  (If this enum isn't yet defined define it now.)

  2.  With the field in question selected, in the property pane change the Type property to the name of your enum (just type it in, it won't appear in the dropdown list.)  That's all you need to do to get LINQ to map an integer in the db to a .NET enum.  BUT, that's not enough for the Dynamic Data stuff to do its magic.  It seems (as I noted in my previous post) that Dynamic Data out of the box will just not render fields that are of type Enum.  They just don't show up on the generated page.  In order to get them working you need to:

   

  3. In your Dynamic Data web project add two new user controls to the App_Shared/DynamicDataFields folder, Enumeration.ascx and Enumeration_Edit.ascx. 

  The code for Enumeration.ascx is:

  
     

  <%@ Control Language="C#" Inherits="System.Web.DynamicData.FieldTemplateUserControlBase" %>
  
  <script runat="server">
  
  </script>
  
  <%# DataValueString %>

   

  The code for Enumeration_Edit.ascx is:

   

  <%@ Control Language="C#" Inherits="System.Web.DynamicData.FieldTemplateUserControlBase" %>
  
  <script runat="server">
  	private string selectedValue = null;
  
  	protected void Page_Load(object sender, EventArgs e)
  	{
  		selectedValue = EnumDDL.SelectedValue;
  		string[] enumNames = Enum.GetNames(MetaMember.Type);
  		Array.Sort(enumNames);
  		EnumDDL.DataSource = enumNames;
  		EnumDDL.DataBind();
  	}
  
  	private string GetCurrentValue()
  	{
  		//DynamicMetaForeignKeyMember column = (DynamicMetaForeignKeyMember)MetaMember;
  		
  		object value = DataBinder.GetPropertyValue(DataItem, "Status");
  
  		if (value == null)
  			return String.Empty;
  		return value.ToString();
  	}
  	
  	protected override void OnDataBinding(EventArgs e)
  	{
  		base.OnDataBinding(e);
  
  		if (TemplateMode == DynamicTemplateMode.EditItemTemplate)
  		{
  			EnumDDL.SelectedValue = GetCurrentValue();
  		}
  	}
  	
  	protected override void ExtractValues(IOrderedDictionary dictionary)
  	{
  		object val = null;
  
  		if (string.IsNullOrEmpty(selectedValue))
  		{
  			try
  			{
  				val = Enum.Parse(MetaMember.Type, EnumDDL.SelectedValue);
  			}
  			catch { }
  		}
  		else
  		{
  			val = selectedValue;
  		}
  
  		dictionary[DataField] = val;
  	}
  </script>
  
  <asp:DropDownList ID="EnumDDL" runat="server">
  </asp:DropDownList>
  

    

  4. Now that you've got Enumeration handlers the final step is to add a RenderHint to let the Dynamic Data framework know to use the Enumeration user controls to render that field.  You can either do this by adding an attribute to your LINQ class like so:

   

  [RenderHint("MyLocalFieldName", "Enumeration")]
  public partial class MyDBClass
  {
  }

  Or if as in my case you have made a separate ListDetails.aspx page for editing this table then you can simply add RenderHint="Enumeration" to your  asp:DynamicField declarations on the aspx page.

  So is this the 'right' way to use enumerated fields in Dynamic Data? 

  Enum Enumeration LINQ Dynamic Data

  • Edited by stevekain on Jan 28, 2008 07:17 PM
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  davidebb

  Contributor

  7006 Points

  1366 Posts

  Microsoft

  Re: Dynamic Data and Enum-bound fields

  Jan 28, 2008 08:35 PM|LINK

  Very nice!  Yes, this is absolutely the right way of doing it.  In fact, it's a great demonstration of the beneifits of the field template architecture: you can easily add support for a data type that we had not anticipated.

  We'll look into whether we want to support this by default.

  thanks,
  David

  • Marked as answer by ricka6 on Oct 15, 2008 05:39 PM
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  stevekain

  Member

  20 Points

  16 Posts

  Re: Dynamic Data and Enum-bound fields

  Jan 28, 2008 08:52 PM|LINK

   Excellent.  At first this seemed like a very difficult task but once I managed to wrap my head around how the Dynamic Data stuff is actually working the solution became pretty obvious.  The ability to add custom types to the DynamicDataFields templates is really pretty cool.

   

  I do think that you should really consider native enum support similar to what I've done here.  It would be great if this was built in and didn't require a render hint.

   

  Thanks.  Still really liking Dynamic Data! 

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  davidebb

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  Microsoft

  Re: Dynamic Data and Enum-bound fields

  Jan 28, 2008 08:55 PM|LINK

  Thanks Steve, this is really good feedback!

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  vishnu108mis...

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  20 Points

  65 Posts

  Re: Dynamic Data and Enum-bound fields

  Oct 15, 2008 03:39 PM|LINK

  Hi Davidebb

  I read your article about the enum data types.

  I am stuck on a point in enum datatypes, actully I need to assign enum values from the database field. I have no idea how can I do this?

  There is a field CareerTypes in Career Tables. I have to declare enum with the values of CareerTypes from the Career Tables.

  Can you guide me/ wriite a method if possible?

  I will very thankful for your help.

   

   

  Thanks

  Vishnu Narayan MIshra 

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  davidebb

  Contributor

  7006 Points

  1366 Posts

  Microsoft

  Re: Dynamic Data and Enum-bound fields

  Oct 15, 2008 08:22 PM|LINK

  Hi Vishnu,

  Which article about enum types are you referring to?

  Note that this is a very old thread from way before we released, so it would be best to start a new thread to discuss your issue to avoid confusion.

  thanks!
  David

  • Edited by davidebb on Oct 15, 2008 08:25 PM
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  artcolman

  Member

  6 Points

  8 Posts

  Re: Dynamic Data and Enum-bound fields

  Aug 18, 2011 05:36 PM|LINK

  http://msdn.microsoft.com/en-us/library/system.componentmodel.dataannotations.enumdatatypeattribute.aspx

   

  For the Enumeration Data Type Attribute

  http://www.drybridge.com Art Colman

   

  Art Colman
  Drybridge Technologies
  http://www.drybridge.com
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  noman.aftab

  Member

  2 Points

  1 Post

  Re: Dynamic Data and Enum-bound fields

  Sep 20, 2011 06:39 AM|LINK

  I used your code and it didn't compiled and found that there are some changes made by Microsoft which are mentioned here:

  http://www.asp.net/downloads/35-sp1/readme

   FieldTemplateUserControlBase no longer exists. Change any instances of the Inherits attribute that reference the old class to reference the FieldTemplateUserControl class instead.

   MetaMember changed to Column

  DataItem has been changed to Row.

  and so on.

  Here is what it appears after the changes:

  private string selectedValue = null;
  
      protected void Page_Load(object sender, EventArgs e)
      {
          
          selectedValue = EnumDDL.SelectedValue;
          string[] enumNames = Enum.GetNames(Column.ColumnType);
          Array.Sort(enumNames);
          EnumDDL.DataSource = enumNames;
          EnumDDL.DataBind();
      }
  
      private string GetCurrentValue()
      {
          //DynamicMetaForeignKeyMember column = (DynamicMetaForeignKeyMember)MetaMember;
  
          object value = DataBinder.GetPropertyValue(Row, "Status");
  
          if (value == null)
              return String.Empty;
          return value.ToString();
      }
  
      protected override void OnDataBinding(EventArgs e)
      {
          base.OnDataBinding(e);
  
          if (Mode == DataBoundControlMode.Edit)
          {
              EnumDDL.SelectedValue = GetCurrentValue();
          }
      }
  
      protected override void ExtractValues(IOrderedDictionary dictionary)
      {
          object val = null;
  
          if (string.IsNullOrEmpty(selectedValue))
          {
              try
              {
                  val = Enum.Parse(Column.ColumnType, EnumDDL.SelectedValue);
              }
              catch { }
          }
          else
          {
              val = selectedValue;
          }
  
          dictionary[Column.Name] = val;
      }