Old school data binding for List controls in ASP.NET MVC

  • [アーティクル]

The ASP.NET MVC is designed for Performance and extensibility and testability in mind. MVC 1.0 comes with handful of HTML extensions that allows you render textboxes, dropdowns and other controls. While you are creating a DropDownList or List box you may require this little extension to bind your control to existing data source such as Linq2Sql or dataset.

For an example :

 <%= Html.DropDownList("jobcategory", Model.JobCategory)%>

 

 Error 2 Argument '3': cannot convert from 'JobCategoryDataTable' to 
'System.Collections.Generic.IEnumerable' d:\Projects\ShellMvc2\Views\Search\SearchControls.ascx 11 46 ShellMvc2

where Model.JobCategory is the Linq2Sql object collection. I wonder if it was ASP.NET I had DataTextField and DataValueField.

Here we go with custom list extension:

 <%= Html.DropDownList("jobcategory", Model.JobCategory.ToSelectList("JobCategoryId", "JobCategory")%>

Where Model.JobCategory is the data source, this can be any type of IEnumerable source such as IDataReader, DataTable, List2Sql or any CustomObject collection.

First parameter JobCategoryId is the DataDisplayField and the second parameter is the DataValueField. This extension can further be improved by creating custom of IEnumerator<SelectListItem>

 using System.Collections;

 using System.Collections.Generic;

 using System.Web.Mvc;

 using System.Web.UI;

 public static class MyExtensions

 {

     public static IEnumerable<SelectListItem> ToSelectList(this IEnumerable collection, string displayField, string valueField)

     {

         return ToSelectList(collection, displayField, valueField, null);

     }

  

     public static IEnumerable<SelectListItem> ToSelectList(this IEnumerable collection,
                            string displayField, string valueField, string selectedValue)

     {

         List<SelectListItem> list = new List<SelectListItem>();

         foreach (var item in collection)

         {

             string value = DataBinder.GetPropertyValue(item, valueField).ToString();

             list.Add(new SelectListItem

             {

                 Text = DataBinder.GetPropertyValue(item, displayField).ToString(),

                 Value = value,

                 Selected = (value.Equals(selectedValue))

             });

         }

         return list;

     }

 }

Comments

  • Anonymous
    August 25, 2009
    qGreetings all. I was just wondering if any of you keep your Path of Asura set to one specific place or if you change it depending on where you are questing. I initially would change mine all of the time; however, to have aoc gold is very important while you playing the game, now being at lvl 71, I have found that keeping it set to Conarch village is most convenient. There is a wagoneer close to the Wayseer of Asura in Conarch who will take you to all places in Cimmeria(Fields of the Dead, Ymir's Pass, Atzel's Approach) and to Old Tarantia (where then you can quickly go to the Aquilonia wagoneer or take the boat to Stygia). Before I found him, I hated having to go through C. Valley to get to the FotD....blah.