ASP.NET MVC

Re: problem with how I use ActionResult / trying to return List of simple class def

pkellner — Wed, 10 Sep 2008 04:52:20 GMT

Thanks! I appreciate all the time you spent answering my questions. Very helpful.

Re: problem with how I use ActionResult / trying to return List of simple class def

freechoice — Wed, 10 Sep 2008 01:40:22 GMT

Scott has said that:"Preview 5" doesn't have a built-in [Bind] attribute like above just yet (although we are considering adding it as a built-in feature of ASP.NET MVC in the future). However all of the framework infrastructure necessary to implement a [Bind] attribute like above is now implemented in preview 5. The open source MVCContrib project also has a DataBind attribute like above that you can use today.

So you can not use the Bind attribute in this version(Maybe the next version,and the version maybe a first beta version), But that dosn't means that you could not use ModelBinder in this version,If you wanna use ModelBinder,You need to do the following steps.

1,Write your own ModelBinder,Here is Mine(Thanks to chsword)

1    using System;
2    using System.Collections.Generic;
3    using System.ComponentModel;
4    using System.Globalization;
5    using System.Linq;
6    using System.Web.Mvc;
7    
8    namespace CMS.Models
9    {
10       public class CMSModelBinder:IModelBinder
11       {
12           #region IModelBinder Members
13   
14           public object GetValue(ControllerContext controllerContext, string modelName, Type modelType, ModelStateDictionary modelState)
15           {
16               //Instant Model Type
17               object model = Activator.CreateInstance(modelType);
18               //Get the Object property collections
19               IEnumerable<string> keys = modelType.GetProperties().Select(c => c.Name);
20               //Object Prefix，if the passing modelName is content,Will check name="content.ID" name="content.title"
21               string objectPrefix = modelName;
22               //Property Collections
23               PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(model);
24               var dictionary = new Dictionary<string, PropertyDescriptor>();
25         
26               foreach (string str in keys)
27               {
28                   if (!string.IsNullOrEmpty(str))
29                   {
30                       PropertyDescriptor descriptor = properties.Find(str, true);
31                       if (descriptor == null)
32                       { 
33                           throw new ArgumentException(
34                               string.Format(CultureInfo.CurrentCulture,"Property dosn't exists：{0},{1}",new object[]{model.GetType().FullName,str}),"modelName");
35   
36                       }
37                       //Link the object and property names

38                       string str3 = string.IsNullOrEmpty(objectPrefix) ? str : (objectPrefix + "." + str);
39                       dictionary[str3] = descriptor;
40                   }
41               }
42               foreach (var pair in dictionary)
43               {
44                   string key = pair.Key;
45                   PropertyDescriptor descriptor2 = pair.Value;
46                   object obj2 = ModelBinders.GetBinder(descriptor2.PropertyType).GetValue(controllerContext, key, descriptor2.PropertyType, modelState);
47                   if (obj2!=null)
48                   {
49                       try
50                       {
51                           //Set the Property Value
52                           descriptor2.SetValue(model, obj2);
53                           continue;
54                       }
55                       catch
56                       {
57                           //If we have a Vaildation Helper，It will shown in Html.ValidationSummary中
58                           string errorMessage = string.Format(CultureInfo.CurrentCulture, "Validation failed{0}：{1}", new[] { obj2, descriptor2.Name });
59                           string attempedValue = Convert.ToString(obj2, CultureInfo.CurrentCulture);
60                           modelState.AddModelError(key, attempedValue, errorMessage);
61                           continue;
62                       }
63                   }
64               }
65               //At last return the object
66               return model;
67           }
68   
69           #endregion
70       }
71   }

2) you need to register ModelBinders

 1            [AcceptVerbs("POST")]
2            public ActionResult Create([ModelBinder(typeof(CMSModelBinder))]ArticleAdd article)
3            {}

3) The View Page

<span class="message">
    <%= ViewData["Message"]%>
</span>
<%= Html.ValidationSummary() %>
    <% using (Html.Form("Article","Create",FormMethod.Post)) { %>
        <table width="98%">
            <tr>
                <td>Title：</td>
                <td>
                    <%= Html.TextBox("article.title") %>
                    <%=Html.ValidationMessage("title","*") %>
                </td>
            </tr>
            <tr>
                <td>Alias：</td>
                <td><%= Html.TextBox("article.alias") %></td>
            </tr>

</table>

Re: problem with how I use ActionResult / trying to return List of simple class def

pkellner — Tue, 09 Sep 2008 18:07:29 GMT

Thanks FreeChoice1 (interesting name BTW). Your solution worked great.

I'm wondering if there is another way that works somehow with the [bind] attribute. On Preview 5 from ScottGu's blog, his example has a class which I'm pasting below. It is specifically for product, but maybe it has relevance to the general case.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using MvcApplication49.Models;

namespace MvcApplication49.Controllers
{
    //
    // This file shows an example of a custom IModelBinder. This implementation creates a Product object
    // from form post values. Note that you typically wouldn't create a custom IModelBinder per type.
    // Instead you'd use a more generic binder like [Bind] which would handle all of your types.
    //

    public class ProductBinder : IModelBinder
    {
        //
        // Helper Methods
        //

        private static string Concat(string modelName, string propertyName)
        {
            return (String.IsNullOrEmpty(modelName)) ? propertyName : modelName + "." + propertyName;
        }

        private static T LookupValue<T>(ControllerContext controllerContext, string propertyName, ModelStateDictionary modelState)
        {
            IModelBinder binder = ModelBinders.GetBinder(typeof(T));
            object value = binder.GetValue(controllerContext, propertyName, typeof(T), modelState);
            return (value is T) ? (T)value : default(T);
        }

        //
        // IModelBinder Member Implementation
        //

        public object GetValue(ControllerContext controllerContext, string modelName, Type modelType, ModelStateDictionary modelState)
        {
            if (controllerContext == null)
            {
                throw new ArgumentNullException("controllerContext");
            }
            if (modelType != typeof(Product))
            {
                throw new ArgumentException("This binder only works with Product models.", "modelType");
            }

            // Instantiate an product object, then bind values to each property
            Product e = new Product()
            {
                ProductName = LookupValue<string>(controllerContext, Concat(null, "ProductName"), modelState),
                UnitPrice = LookupValue<Decimal>(controllerContext, Concat(null, "UnitPrice"), modelState),
                ReorderLevel = LookupValue<short>(controllerContext, Concat(null, "ReorderLevel"), modelState),
                Discontinued = LookupValue<Boolean>(controllerContext, Concat(null, "Discontinued"), modelState)
            };
            return e;
        }
    }
}

Re: problem with how I use ActionResult / trying to return List of simple class def

freechoice — Tue, 09 Sep 2008 17:16:28 GMT

As you see,the Return for the Index in the Controller is ActionResult

So you need to return an ActionResult type,right?

maybe you could try that

1    public ActionResult Index()
2    {
3        ContactList member = yourBusiness.GetMembers();
4        return View("Index",member);
5    }
6    
7    You could use ModelData in your View Page

Hope that can help you.

problem with how I use ActionResult / trying to return List of simple class def

pkellner — Tue, 09 Sep 2008 17:03:07 GMT

Following Scott Guthrie's example from preview 5, I've tried to create my own controller that returns a list of generic items. I'm getting the error "can not convert..." as below

My business class is just a simple list of

/// <summary>

/// This is the DataItem that is used in the methods of the class above

/// </summary>

public class BusinessObjectItem

{

private bool approved;

private DateTime createDate;

private string email;

private int id;

private string name;public BusinessObjectItem()

{

}

public BusinessObjectItem(BusinessObjectItem bo)

{

id = bo.id;

name = bo.name;

email = bo.email;

approved = bo.approved;

createDate = bo.createDate;

return;

}

public BusinessObjectItem(int id, string name, string email, bool approved, DateTime createDate)

{

this.id = id;

this.name = name;

this.email = email;

this.approved = approved;

this.createDate = createDate;return;

}

[DataObjectField(true)]

public int Id

{

get { return id; }set { id = value; }

}

[DataObjectField(false)]

public string Name

{

get { return name; }

set { name = value; }

}