MVC3字典未绑定到模型 [英] MVC3 Dictionary not binding to model
问题描述
我有一个包含字典属性的模型. (这已从一个较大的项目中提取到了这个示例中,我已经确认仍然存在相同的问题)
I have a model that contains a dictionary property. (this has been distilled from a larger project into this example, which I have confirmed still has the same issue)
public class TestModel
{
public IDictionary<string, string> Values { get; set; }
public TestModel()
{
Values = new Dictionary<string, string>();
}
}
控制器
public class TestController : Controller
{
public ActionResult Index()
{
TestModel model = new TestModel();
model.Values.Add("foo", "bar");
model.Values.Add("fizz", "buzz");
model.Values.Add("hello", "world");
return View(model);
}
[HttpPost]
public ActionResult Index(TestModel model)
{
// model.Values is null after post back here.
return null; // I set a break point here to inspect 'model'
}
}
和一个视图
@using TestMVC.Models
@model TestModel
@using (Html.BeginForm())
{
@Html.EditorFor(m => m.Values["foo"]);
<br />
@Html.EditorFor(m => m.Values["fizz"]);
<br />
@Html.EditorFor(m => m.Values["hello"]);
<br />
<input type="submit" value="submit" />
}
这将呈现给浏览器,如下所示:
This renders to the browser like this:
<input class="text-box single-line" id="Values_foo_" name="Values[foo]" type="text" value="bar" />
我遇到的问题是回发后字典在模型上为null.
The problem I'm having is that the dictionary is null on the model after postback.
- 我这样做正确吗,还是有更好的方法?
我需要某种键值存储,因为表单上的字段是可变的,所以我不能使用POCO模型.
I need to have some kind of key-value storage, as the fields on my form are variable, so I can't use a POCO model.
推荐答案
正如@Blast_Dan和@gprasant所述,模型绑定程序期望输入元素的名称属性采用Property[index].Value
格式,其中index
是int
,而Value
是KeyValuePair
类的属性之一.
As @Blast_Dan and @gprasant mentioned, the model binder is expecting the name attribute of the input element to be in the format Property[index].Value
, where index
is an int
and Value
is one of the properties on the KeyValuePair
class.
不幸的是,@Html.EditorFor
以错误的格式生成了该值.我写了一个HtmlHelper扩展名,将name属性转换为正确的格式:
Unfortunately, @Html.EditorFor
generates this value in the wrong format. I wrote an HtmlHelper extension to transform the name attribute to the correct format:
public static IHtmlString DictionaryEditorFor<TModel, TProperty, TKey, TValue>(this HtmlHelper<TModel> Html, Expression<Func<TModel, TProperty>> expression, IDictionary<TKey, TValue> dictionary, DictionaryIndexRetrievalCounter<TKey, TValue> counter, string templateName, object additionalViewData)
{
string hiddenKey = Html.HiddenFor(expression).ToHtmlString();
string editorValue = Html.EditorFor(expression, templateName, additionalViewData).ToHtmlString();
string expText = ExpressionHelper.GetExpressionText(expression);
string indexText = expText.Substring(expText.IndexOf('[')).Replace("[", string.Empty).Replace("]", string.Empty);
KeyValuePair<TKey, TValue> item = dictionary.SingleOrDefault(p => p.Key.ToString() == indexText);
int index = counter.GetIndex(item.Key);
string key = hiddenKey.Replace("[" + indexText + "]", "[" + index + "].Key").Replace("value=\"" + item.Value + "\"", "value=\"" + item.Key + "\"");
string value = editorValue.Replace("[" + indexText + "]", "[" + index + "].Value");
return new HtmlString(key + value);
}
因为整数索引必须遵循以下规则:
Because the integer index must follow these rules:
-
必须从0开始
Must start with 0
必须不间断(例如,您不能从3跳到5)
Must be unbroken (you can't skip from 3 to 5, for example)
我写了一个计数器类来为我处理整数索引:
I wrote a counter class to handle getting the integer index for me:
public class DictionaryIndexRetrievalCounter<TKey, TValue>
{
private IDictionary<TKey, TValue> _dictionary;
private IList<TKey> _retrievedKeys;
public DictionaryIndexRetrievalCounter(IDictionary<TKey, TValue> dictionary)
{
this._dictionary = dictionary;
this._retrievedKeys = new List<TKey>();
}
public int GetIndex(TKey key)
{
if (!_retrievedKeys.Contains(key))
{
_retrievedKeys.Add(key);
}
return _retrievedKeys.IndexOf(key);
}
}
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