Ricka on MVC & Dynamic Data

Should my database calls be Asynchronous?

2009-11-14T01:10:02Z

Long running/expensive database calls might seem like a natural candidate for asynchronous calls. Suppose you have the following system: A web application running on IIS 7 /.NET Framework v3.5 SP1 using the default request gating ( maxConcurrentRequestsPerCPU ="12") Your server is a dual. You are not using asynchronous methods. Your web application contains a mix of static content, quick running dynamic pages, and a few very slow pages that hit the DB. (The DB is the bottleneck on these...(read more)

Tips on getting your ASP.NET MVC questions answered quickly

2009-10-29T21:22:00Z

When you run into an issue or have a question about ASP.NET MVC the best place for it is the MVC Forum . When you write your question, there are a few simple things that you can do to make it easier for the ‘experts’ to answer (and hence to get an answer quicker!). 1. Mention what environment you’re running in What web server are you using Most likely, you are using either “Cassini” (the test web server built in Visual Studio), IIS6 (XP), or IIS7 (on Vista, Windows 7 or Windows Server 2008). In many...(read more)

MVC FAQ

2009-10-15T19:43:00Z

Technorati Tags: MVC Please post corrections/submissions to the MVC Forum . Include MVC FAQ in the title. Post LINQ to SQL To SQL Questions here Post Entity Framework Questions here Q: How do I get started with MVC? Walkthrough: Creating a Basic MVC Project with Unit Tests in Visual Studio Walkthrough: Using Templated Helpers to Display Data Includes a VB/C# sample. (Requires MVC 2) How to: Validate Model Data Using DataAnnotations Attributes (Shows how to use Entity Framework with MVC) Includes...(read more)

Client Side Validation for MVC 2 P2

2009-10-03T02:30:00Z

MVC 2 Preview 1 added support for DataAnnotations . In my MSDN article How to: Validate Model Data Using DataAnnotations Attributes I covered the basics of validation. Preview 2 adds client validation with the addition of one line of code. The following class contains the model I use in my sample download . public class Pals { [ Required ()] [ Range (33,99)] public float Height { get ; set ; } [ Required ()] [ StringLength (7)] public string Name { get ; set ; } [ ScaffoldColumn ( false )] public...(read more)

DRY-ing out the MVC 2 Templated Helpers

2009-08-18T22:15:00Z

In my MSDN article Using Templated Helpers to Display Data , I show how they provide a very productive means of building a UI for data sets. The code below shows a typical use of the Display and Label helpers. <% = Html.Label( "Name" ) %> : <% = Html.Display( "Name" ) %> <% = Html.LabelFor(Pals => Pals.ID) %> : <% = Html.DisplayFor(Pals =>...(read more)

Using DataAnnotations in MVC 2 - Catching up to Dynamic Data

2009-08-01T10:39:00Z

DataAnnotations help you write robust validation and prevent the type of annoying error message shown above. Form submittal failure when a field doesn’t validate can be very frustrating - especially when there is no indication of the problematic property or the constraint violation. I happened to get the Outlook error above when I attempted to submit a mail message to the MVC QA guys. It turns out the distribution list I made for them a few days earlier had problems. The image below (From my sample...(read more)

New Templated Helpers Improve SoC

2009-07-24T04:08:15Z

SoC (from WikiPedia) In my MSDN article Walkthrough: Using Templated Helpers to Display Data I show how to annotate your data model to specify that a field should be rendered with a type-specific control. The download sample code also includes a control using the new Html.EditorFor helper. With one line of code you can open an editor on your strongly typed object. Using the line below, my edit/create view can instantiate an editor on the Product object. <% = Html.EditorFor(Product=> Model)...(read more)

Setting font attributes with UIHint in your Entity Partial Class

2009-06-02T17:41:00Z

I've written a simple Field Template ( RedBold.ascx ) that reads most font attributes and applies them to your field values. The new entity templates make it easy to apply font attributes to the field labels. The image below shows several font attributes applied to the partial class for the Customer table of the AdventureWorksLT database. You can apply attributes (bold, italic, foreground color, background color, border style, border color, font name, etc) to the field name or the field value. For...(read more)

Dynamic Data FAQ

2009-01-08T13:03:00Z

Please post corrections/new submissions to the Dynamic Data Forum. Put FAQ Submission/Correction in your title.

See Tips on getting your ASP.NET Dynamic Data questions answered quickly

Post LINQ To SQL Questions here
Post Entity Framework Questions here

Links that will answer questions:

From the Dynamic Data architect David Ebbo

From http://blogs.msdn.com/rickAndy (Most samples include VB)

Explicit connection string for EF and L2S
Custom Validation Error message not displayed
Improving the FK field display: Showing two fields in Foreign Key columns
How to create an updateable view with ADO Entity Framework and with LINQ to SQL
Tweaking the Filter Repeater When you have too many FK to display in the filter repeater.

From ASP.Net Developer David Fowler

Q: How do I get started with Dynamic Data?
A: If you like videos, see ASP.NET Dynamic Data videos
     MSDN on Dynamic Data
     Walkthrough: Creating a New ASP.NET Dynamic Data Web Site Using Scaffolding
     http://www.asp.net/dynamicdata/
     Dynamic Data Forum

Q: What's new with Dynamic Data for .Net 4 Beta? <-- New
A: See this link.

Q: The data annotation to my partial class is not working?
A: The most common problem is no namespace or incorrect namespace around your partial class. A partial class that is not part of the data model (or part of another class) is known as a naked partial class. The easiest way to test if you have a naked partial class is to add a non-existing field to the partial class. In the following snippet, bogus is not in the CustomerAddress table.

[MetadataType(typeof(CustomerAddressMetaData))]
   public partial class CustomerAddress {
       public class CustomerAddressMetaData {

           [ScaffoldColumn(false)]
           public object ModifiedDate;

           public object bogus;
       }
   }

When you run the Dynamic Data project, you will get the following exception in DefaultModel.RegisterContext (in global.asax):

The associated metadata type for type 'DynamicDataProject.CustomerAddress' contains the following unknown properties or fields: bogus. Please make sure that the names of these members match the names of the properties on the main type.

Q: How do I generate GUIDs on inserts?
A: You don't, you shouldn't. Let the DB generate them or you will have performance problems. You can modify the data model XML and explicitly state they are DB generated. With the EDM, use StoreGeneratedPattern="Computed" while Linq to SQL uses IsDbGenerated="true"

Q: How to set Displayformat for a password field?
A: See Steve's excellent Password FieldTemplates for Dynamic Data

Q: How do I check for duplicates before I insert? (Or get values from the DB for any reason before I insert)
A: see this post.

Q: How do I mark a columns as read-only?
A: see this post or Making a Field Read-Only via the ReadOnlyAttribute – Dynamic Data - Note the next version of Dynamic Data And The ASP.NET Dynamic Data 4.0 Preview 3 support the [ReadOnly(true)] attribute.

Q: Can Dynamic Data use a data model generated by a 3rd party O/RM tool?
A:The current Dynamic Data needs the following items to work with a technology:
-    Technology must support Linq
-    DataSource control must exist for the technology
-    Dynamic Data ModelProvider must exist for the technology

An example of one today is LLBLGen: http://www.llblgen.com/defaultgeneric.aspx

nHibernate currently does not meet the Linq requirements.

Q: What DB's are supported?
A: See ADO.NET Entity Framework Providers

Q: How do I hide columns from the Edit and other page templates?
A: Suppose you want to display the Salary field, but you don't want to show it in the Edit and Insert templates. See Stephens popular tutorial

Dynamic Data - Hiding Columns in selected PageTemplates

Q: How do I disallow navigation links on Foreign Key columns?
A: By default, DD displays the first string column in the Foreign Key table in stead of the FK. This is rendered as a link (NavigateUrl) to the FK table. If you're not happy with the default (column shown) use the DisplayColumn attribute on the FK table to specify which property is displayed. See also Improving the FK field display: Showing two fields in Foreign Key columns. Back to the original question. The easiest way to disable the FK property from being a NavigateUrl is to hide the FK table by annotating your entity partial class with the ScaffoldTable attribute. Note, ScaffoldTable will hide your table. If you want to expose your table but disable the hyperlink - see Stephens excellent blog Allow Navigation on ForeignKey FieldTemplate – Dynamic Data

Q: How do I move the Edit Delete Details links from the left side (column 0) to the right side of the table.
A: Create your own IAutoFieldGenerator.GenerateFields and add the command field at the end. (thx David Fowler). See this post.

Q: How do I implement role based security? (tables/columns visibility dependent on users role).
A: See this post, and custom IAutoFieldGenerator

Q: How do map stored procedures (sprocs) to Inserts and get back the auto generated PK using L2S?
A: See LINQ to SQL (Part 7 - Updating our Database using Stored Procedures) , Stored Procedures (LINQ to SQL) and How to override default insert method of Details View in Dynamic Data .

Custom Validation Error message not displayed

2009-01-01T01:44:00Z

A customer pointed out that his Spanish validation error messages were not being displayed; the default Error message was shown instead. I'll use the Products table from the NorthWind Db to reproduce the problem and show a work-around.

Create a partial class for the Products entity:

 [MetadataType(typeof(ProductsMD))]
    public partial class Products {
        public class ProductsMD {
            [DataType("dummy", ErrorMessage = "El campo debe ser un entero positivo")]
            [DisplayName("En la acción")]
            public object UnitsInStock { get; set; }
        }
    }

VB

    <MetadataType(GetType(ProductsMD))> _
Public Class Products
        Public Class ProductsMD
            <DataType("dummy", ErrorMessage:="El campo debe ser un entero positivo"), _
             DisplayName("En la acción")> _
            Public Property UnitsInStock() As Object
            End Property
        End Class
    End Class

Navigate to the Products table, edit a row, and change the UnitsInStock to a letter. Select update and you will get a default error message, not the message applied with the DataType attribute.

The example above was doomed to failure as the DataType attribute above does not match the DataType enum or have a matching field template.

There are a couple of possible solutions for displaying custom validation errors on integer conversion failure. You can add the compare validator message that will be displayed for any validation error. The code should be added as the last statement of the Page_Load method in the DynamicData\FieldTemplates\Integer_Edit.ascx.cs (or .vb) file.

CompareValidator1.ErrorMessage = String.Format("El campo {0} debe ser un entero", Column.DisplayName);

or for VB

CompareValidator1.ErrorMessage = String.Format("El campo {0} debe ser un entero", Column.DisplayName)

Entering a non-integer such as Z to the units in stock field now yields the following error message:

El campo En la acción debe ser un entero

Adding the CompareValidator1.ErrorMessage to the integer template works for every scaffolded integer.

For more flexibility, you can extract the custom message from the data model partial class. Replace the CompareValidator1.ErrorMessage line above with the following in the Page_Load method.

 var dataTypeAttribute = MetadataAttributes.OfType<DataTypeAttribute>().SingleOrDefault();

 if (dataTypeAttribute != null) {
    CompareValidator1.ErrorMessage = dataTypeAttribute.FormatErrorMessage(Column.DisplayName);
 }

Dim dataTypeAttribute = MetadataAttributes.OfType(Of DataTypeAttribute)().SingleOrDefault() 

If dataTypeAttribute IsNot Nothing Then 
    CompareValidator1.ErrorMessage = dataTypeAttribute.FormatErrorMessage(Column.DisplayName) 
End If

Even simpler than adding a dummy attribute and extracting the error message; use the RegularExpression attribute and allow only positive integers. The following snippet fixes the error message problem without requiring you to extract the error message in the Page_Load method.

  [MetadataType(typeof(ProductsMD))]
    public partial class Products {
        public class ProductsMD {
  //          [DataType("dummy", ErrorMessage = "El campo debe ser un entero positivo")]
            [RegularExpression(@"^0*[1-9][0-9]*$", ErrorMessage = "Must be a entero positivo")]
            [DisplayName("En la acción")]
            public object UnitsInStock { get; set; }
        }
    }

VB

<MetadataType(GetType(ProductsMD))> _ 
Public Partial Class Products 
    Public Class ProductsMD 
Private _UnitsInStock As Object 
        ' [DataType("dummy", ErrorMessage = "El campo debe ser un entero positivo")] 
        <RegularExpression("^0*[1-9][0-9]*$", ErrorMessage := "Must be a entero positivo")> _ 
        <DisplayName("En la acción")> _ 
        Public Property UnitsInStock() As Object 
            Get 
                Return _UnitsInStock 
            End Get 
            Set(ByVal value As Object) 
                _UnitsInStock = value 
            End Set 
        End Property 
    End Class 
End Class

Notes:

We are using the DataType attribute as a dummy attribute so we can extract our custom error message when a validation error occurs.
This is a known bug that should be fixed in the next release.

Explicit connection string for EF

2008-12-09T21:05:00Z

The default constructor for the ObjectContext class in the Entity Data Model (EDM) retrieves the construction string from the web.config or app.config file. If you have multiple data models or need to pass in the the construction string at run time you must use the ObjectContext constructor that takes a construction string. (Note: Be sure to see the bug/work-around at the end of this article.) The follow snippet shows how to build the string for integrated security.

//  copy connection string from app.config or web.config  

    // connectionString="metadata=res://*;
    // provider=System.Data.SqlClient;
    // provider connection string=&quot;
    // Data Source=ricka0;Initial Catalog=Northwind;Persist Security Info=True;
    // User ID=sa;Password=*(IU89iu;MultipleActiveResultSets=True&quot;"
    // providerName="System.Data.EntityClient" 
    

    public static string UglyConStr() {

        return "metadata=res://*;"
          + "provider=System.Data.SqlClient;"
          + "provider connection string=';"  // Replace &quot with ' (single quote)
        + "Data Source=ricka0;"
        + "Initial Catalog=Northwind;"
        + "Persist Security Info=True;"
        + "User ID=sa;Password=*(IU89iu;"
        + "MultipleActiveResultSets=True';"  // Replace &quot with ' (single quote)
            //    + "providerName=\"System.Data.EntityClient\""
        ;
    }

While the construction string above works, it's very ugly. The hair pulling trick to get it working is replacing &quot with a single quote ' as shown in the comments. Using the raw connection string from the config file (using &quot ) results in a misleading error message Keyword not supported: 'data source'.

A much more elegant construction string using SQL connection is shown below.

 public static string getConStrSQL() {

        string connectionString = new System.Data.EntityClient.EntityConnectionStringBuilder
        {
            Metadata = "res://*",
            Provider = "System.Data.SqlClient",
            ProviderConnectionString = new System.Data.SqlClient.SqlConnectionStringBuilder
            {
                InitialCatalog = "Northwind",
                DataSource = "ricka0",
                IntegratedSecurity = false,
                UserID = getUID(),                 // User ID such as "sa"
                Password = getPWD(),               // hide the password
            }.ConnectionString
        }.ConnectionString;

        return connectionString;
    }

In VB:

Public Shared Function getConStrSQL() As String
     Dim connectionString As String = New System.Data.EntityClient.EntityConnectionStringBuilder() _
         With {.Metadata = "res://*", _
               .Provider = "System.Data.SqlClient", _
               .ProviderConnectionString = New System.Data.SqlClient.SqlConnectionStringBuilder() _
                 With {.InitialCatalog = "Northwind", _
                       .DataSource = "ricka0", _
                       .IntegratedSecurity = False, _
                       .UserID = getUID(), _
                       .Password = getPWD()}.ConnectionString}.ConnectionString
     Return connectionString
 End Function

The integrated security approach is slightly different.

public static string getConStrIntegrated() {

        string conStrIntegratedSecurity = new System.Data.EntityClient.EntityConnectionStringBuilder
           {
               Metadata = "res://*",
               Provider = "System.Data.SqlClient",
               ProviderConnectionString = new System.Data.SqlClient.SqlConnectionStringBuilder
               {
                   InitialCatalog = "NorthwindEF",
                   DataSource = "bing0",
                   IntegratedSecurity = true,
               }.ConnectionString
           }.ConnectionString;

        return conStrIntegratedSecurity;
    }

For Dynamic Data, simply pass the construction string to the MetaModel RegisterContext as follows.

 public static void RegisterRoutes(RouteCollection routes) {
        MetaModel model = new MetaModel();


        model.RegisterContext(() => new NorthwindModel.NorthwindEntities(getConStrIntegrated()),
            new ContextConfiguration()
            {
                ScaffoldAllTables = true
            });

        // Routes omitted for clarity
    }

Unfortunately, the current version of Dynamic Data doesn't support this approach with EF (L2S does work). To get the page templates to use the connection string you must add the following line to the Page_Load method in the page templates.

GridDataSource.ContextCreating += delegate(object ceSender, System.Web.UI.WebControls.EntityDataSourceContextCreatingEventArgs ceArgs) {
            ceArgs.Context = (System.Data.Objects.ObjectContext)table.CreateContext();
        };

The complete Page_Load is below

protected void Page_Load(object sender, EventArgs e) {
        table = GridDataSource.GetTable();

         GridDataSource.ContextCreating += delegate(object ceSender, System.Web.UI.WebControls.EntityDataSourceContextCreatingEventArgs ceArgs) {
            ceArgs.Context = (System.Data.Objects.ObjectContext)table.CreateContext();
        }; 

        Title = table.DisplayName;
        GridDataSource.Include = table.ForeignKeyColumnsNames;
        InsertHyperLink.NavigateUrl = table.GetActionPath(PageAction.Insert);

        // Disable various options if the table is readonly
        if (table.IsReadOnly) {
            GridView1.Columns[0].Visible = false;
            InsertHyperLink.Visible = false;
        }
    }

Improving the FK field display: Showing two fields in Foreign Key columns

2008-11-22T06:17:00Z

The default scaffold of the CustomerAddress table in the AdventureWorksLT database poses a problem: Dynamic Data (DD) defaults to using the first string field in the referenced table. In this case, the first string field is the Title field (Mr,Ms, and so on). The image below shows the problem with the FilterRepeater drop down list and Customer column elements.

We can take a first step toward fixing this issue by creating and annotating a partial class for the Customer entity. The code below now displays the LastName field for the customer entity. The DisplayColumn attribute tells referring entities which column to use for display instead of the Foreign Key field.

 [DisplayColumn("LastName")]
 [MetadataType(typeof(CustomerMetaData))]
 public partial class Customer {
      public class CustomerMetaData {
   }
 }

While the resulting view is an improvement, it’s not there yet. Note that it doesn't distinguish between the customers with non-unique last names, such as Adams or Liu.

To fix this, we overload the ToString method for the Customer partial class as shown below:

// [DisplayColumn("LastName")]
[MetadataType(typeof(CustomerMetaData))]
public partial class Customer {

     public override string ToString() {
         return LastName.ToString() + ", " + FirstName.ToString();
     }

     public class CustomerMetaData {

}

The resulting display gets it right: the code now shows the correct field, and it distinguishes between David, Jinghao and Kevin Liu.

Special thanks to David Ebbo for recommending the ToString() approach and Phil Haack for granting me blog dibs.

How to create an updateable view with ADO Entity Framework and with LINQ to SQL

2008-10-04T05:07:00Z

Creating an update-able view with ADO Entity Framework (EF) or LINQ to SQL (L2S) is a fairly advanced topic and not directly associated with Dynamic Data. At the end of the article I have a sample console application to verify the modified L2S data model allows updates on a view. To create an update-able view, you must modify the wizard (or other tool) generated XML file (data model). Each time you generate a new data model (for example when the schema changes), you will need to reapply these steps.

ADO Entity Framework (EF) makes views Read Only via the <DefiningQuery> element. You make the data model view update-able by removing the <DefiningQuery> element and making a few minor changes. Note the example below is a very simple view on one table and includes the primary key.

This is what I did to make an update-able view for the AdventureWorksLT DB

CREATE VIEW [SalesLT].[vAddr]
AS
SELECT AddressID,[AddressLine1],[City],[StateProvince],[CountryRegion],[PostalCode]
FROM [AdventureWorksLT2008].[SalesLT].[Address]

The next line shows this view is update-able (at least from T-SQL)

UPDATE vAddr SET PostalCode = '54321'
WHERE addressID > 11382 AND
StateProvince = 'WA'

 (18 row(s) affected)

Edit the EF SSDL, comment out the <DefiningQuery> , remove store: prefix from Schema="SalesLT" and remove store:Name="vAddr" . The commented/changed code below

</EntityContainer>

LINQ to SQL is the simplest.

Using the view above,

Simply change the following line in the wizard generated code to use AutoSync = AutoSync.OnInsert in lieu of AutoSync=AutoSync.Always on the AddressID property.

// [Column(Storage="_AddressID", AutoSync=AutoSync.Always, DbType="Int NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)]
[Column(Storage = "_AddressID", AutoSync = AutoSync.OnInsert, DbType = "Int NOT NULL IDENTITY", IsPrimaryKey = true, IsDbGenerated = true)]
public int AddressID

The following example shows how to test the view from a console application.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Linq;
using System.Data.Linq.Mapping;

namespace updateableView {

        public class T {
            public LTDataContext db;
            //    readonly string con = "Data Source=bing0;Initial Catalog=AdventureWorksLT2008;Integrated Security=True";
            readonly string con = "Data Source=bing0;Initial Catalog=AdventureWorksLT2008;" +
                                   "Persist Security Info=True;User ID=sa;Password=*(IU89iu";

            public T() {
                db = new LTDataContext(con);
            }

            public void addAddr(string city) {

                vAddr adr = new vAddr();
                adr.AddressLine1 = "1234 N St.";
                adr.City = city;
                adr.PostalCode = "99966";
                adr.StateProvince = "Mt";
                adr.CountryRegion = "None";

                db.vAddrs.InsertOnSubmit(adr);
                db.SubmitChanges();
            }

            public void tq(string city) {

                Table<vAddr> addr = db.GetTable<vAddr>();
                var q = from c in addr
                        where c.City == city
                        select c;

                foreach (var cst in q)
                    Console.WriteLine("id = {0}, City = {1}", cst.AddressID, cst.City);
            }
        }

        class Program {
            static void Main(string[] args) {
                T tdb = new T();
                string city = "GF";
                tdb.addAddr(city);
                tdb.tq(city);

            }
        }
    }

Tweaking the Filter Repeater

2008-09-25T22:58:00Z

The default implementation of Dynamic Data provides a drop down list box for each foreign key and boolean field in a table. The drop down list allows you to filter the table with the value selected from the drop down list box. The figure below shows a view of the Product table from the AdventureWorksLT database. Several columns are not displayed because the scaffoldcolumnattribute was applied.

The figure below shows the Product table again after Mountain Bikes is selected in the ProductCategory drop down list. Only products with product category Mountain Bikes are displayed.

The drop down list box is implemented in Dynamic Data by the FilterUserControl.ascx user control in the DynamicData\Content folder. While the filter user control is useful to filter a table when there are a relatively few foreign keys used as categories, it can be unmanageable on tables with hundreds or more foreign keys. For example, the CustomerAddress table of the AdventureWorksLT database has over 400 AddressID foreign keys, and each foreign key points to only one address of a customer (either the Main Office or the Shipping address).

When the foreign key field displayed by the filter user control is a very long string, the drop down list box can move off the browser window. This document will offer and approach to limit the width of the drop down list box. The figure below shows the ProductModelProductDescriptions from the AdventureWorksLT database.

In this blog I show how I like to establish a maximum number of entries in the filter repeater and how to set the maximum width.

Modifying the filter user control to limit number of entries

Editing the filter user control

1. Add a key element to the appSettings Element in the web.config file that will set an upper bound to the number of foreign key entries that will be displayed. The following example sets the upper bound to 55.

<appSettings>
  <add key="FilterUC_FK_limit" value="955"/>
  <add key="FilterUC_Char_limit" value="50"/>
</appSettings>

1 Add a text label to the the filter user control in the FilterUserControl.ascx file found in the DynamicData\Content folder. The following example shows the completed markup.

<%@ Control Language="C#" CodeFile="FilterUserControl.ascx.cs" Inherits="FilterUserControl" %>

<asp:Label ID="LBL1" runat="server" Text="Label" ForeColor= "Brown" Font-Bold="true" />
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="true" EnableViewState="true" CssClass="droplist">
    <asp:ListItem Text="All" Value="" />
</asp:DropDownList>

3. Add a string property to the FilterUserControl. For example, add a property with the name LBL_Txt that will be used to set the label we added to the FilterUserControl.aspx file in a previous step.

4. Add the Page_PreRender method in the FilterUserControl code behind file and set the label text. For example, set the label text with the LBL_Txt property created in the previous step.

5. Modify the Page_Init method in the FilterUserControl code behind file to limit the number of foreign keys displayed. The FilterUC_FK_limit application setting created in the first step will be used to set the maximum number of entries in the drop down list box. The following example shows the completed FilterUserControl code behind file.

Visual Basic

Imports System.Web.DynamicData

Partial Class FilterUserControl
    Inherits System.Web.DynamicData.FilterUserControlBase
    '
    Public LBL_Txt As String
    '
    Public Overrides ReadOnly Property SelectedValue As String
        Get
            Return DropDownList1.SelectedValue
        End Get
    End Property
    '
    Public Event SelectedIndexChanged As EventHandler
    '
    Protected Sub Page_Init(ByVal sender As Object, ByVal e As EventArgs)
        '
        If Page.IsPostBack Then
            Return
        End If
        '
        PopulateListControl(DropDownList1)
        '
        Dim maxCnt As Integer = Convert.ToInt32(ConfigurationManager.AppSettings("FilterUC_FK_limit"))
        If (DropDownList1.Items.Count > maxCnt) Then
            DropDownList1.Visible = False
            LBL1.Visible = False
        End If
        '
        If Not String.IsNullOrEmpty(InitialValue) Then
            DropDownList1.SelectedValue = InitialValue
        End If
        '
    End Sub
    '
    '
    Protected Sub Page_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreRender
        LBL1.Text = LBL_Txt
    End Sub
End Class

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Xml.Linq;
using System.Web.DynamicData;

public partial class FilterUserControl : System.Web.DynamicData.FilterUserControlBase {

    public string LBL_Txt { get; set; }

    public event EventHandler SelectedIndexChanged {
        add {
            DropDownList1.SelectedIndexChanged += value;
        }
        remove {
            DropDownList1.SelectedIndexChanged -= value;
        }
    }

    public override string SelectedValue {
        get {
            return DropDownList1.SelectedValue;
        }
    }

    protected void Page_PreRender(object sender, EventArgs e) {
        LBL1.Text = LBL_Txt;
    }

    protected void Page_Init(object sender, EventArgs e) {

        if (Page.IsPostBack)
            return; PopulateListControl(DropDownList1);

        int maxCnt = Convert.ToInt32(ConfigurationManager.AppSettings["FilterUC_FK_limit"]); 
        if (DropDownList1.Items.Count > maxCnt) {
            DropDownList1.Visible = false;
            LBL1.Visible = false;
        }

        if (!String.IsNullOrEmpty(InitialValue))
            DropDownList1.SelectedValue = InitialValue;
    }
}

5. Remove the original filter label from the page template (list.aspx and listDetails.aspx) and initialize the new label. The original markup is shown below.

<asp:FilterRepeater ID="FilterRepeater" runat="server">
    <ItemTemplate>
       <asp:Label runat="server" Text='<%# Eval("DisplayName") %>' AssociatedControlID="DynamicFilter$DropDownList1" />
        <asp:DynamicFilter runat="server" ID="DynamicFilter" OnSelectedIndexChanged="OnFilterSelectedIndexChanged" />
     </ItemTemplate>
     <FooterTemplate><br /><br /></FooterTemplate>
 </asp:FilterRepeater>

The replacement markup is shown below.

<ItemTemplate>
    <asp:DynamicFilter runat="server" ID="DynamicFilter" LBL_Txt='<%# Eval("DisplayName") %>'
                      OnSelectedIndexChanged="OnFilterSelectedIndexChanged" />
  </ItemTemplate>

Part II: Limiting the width of the filter user control Part II:

To limit the width of the drop down list box, the elements of the list box will be truncated at the maximum allowed character width.Editing the filter user control for maximum characters1. Add a key element to the appSettings Element in the web.config file that will set an upper bound on the number of characters that will be copied to each element of the drop downn list. The key with value FilterUC_Char_limit sets the maximum number of characters to 50.

<appSettings>
  <add key="FilterUC_FK_limit" value="955"/>
  <add key="FilterUC_Char_limit" value="50"/>
</appSettings>

2. Modify the Page_Init method in the FilterUserControl code behind file to limit the number of characters to be copied to the drop down list box. The following example shows how to limit the number of characters.

int maxLen = Convert.ToInt32(ConfigurationManager.AppSettings["FilterUC_Char_limit"]);

for (int i = 0; i < DropDownList1.Items.Count; i++) {
   string s = DropDownList1.Items[i].Text;

   if (s.Length > maxLen) {
      s = s.Substring(0, maxLen - 1);
      s += " ... (see Details for full)";
      DropDownList1.Items[i].Text = s;
   }
}

Visual Basic

Dim maxLen As Integer = Convert.ToInt32(ConfigurationManager.AppSettings("FilterUC_Char_limit"))
   For i As Integer = 0 To DropDownList1.Items.Count - 1

       Dim s As String = DropDownList1.Items(i).Text

       If s.Length > maxLen Then
           s = s.Substring(0, maxLen - 1)
           s += " ... (see Details for full)"
           DropDownList1.Items(i).Text = s
       End If
   Next

The figure below shows the results with the ProductModelProductDescription table.