Question

我正在寻找一种方法将ViewDataDictionary传递给ASP.NET MVC中的部分视图，我采用了这种语法：

new ViewDataDictionary { { "Name", "Value" } }

我对这里的初始化语法有点困惑。有人可以向我解释一下吗？

Answer 1

ViewDataDictionary实施IDictionary<string, object>。

IDictionary<string, object>基本上是KeyValuePair<string, object>。

的集合

您的ViewDataDictionary初始化程序（外部花括号）包含另一组花括号，表示KeyValuePair<string, object>初始化程序。

this answer中解释了可行的原因。

您可以通过逗号分隔Add初始值设定项来KeyValuePair<string, object>多个项目：

var data = new ViewDataDictionary { { "Name", "Value" }, { "Name2", "Value2" } };

同样：

var data = new ViewDataDictionary 
         { 
             new KeyValuePair<string, object>("Name", "Value"), 
             new KeyValuePair<string, object>("Name2", "Value2") 
         };

基本上，内部花括号是初始化KeyValuePair<string, object>对象的好语法。

Answer 2

我使用扩展方法解决了这个问题：

/// <summary>
/// Use this extension method to create a dictionary or objects
///     keyed by their property name from a given container object
/// </summary>
/// <param name="o">Anonymous name value pair object</param>
/// <returns></returns>
public static Dictionary<string, object> ToDictionary(this object o)
{
    var dictionary = new Dictionary<string, object>();

    foreach (var propertyInfo in o.GetType().GetProperties())
    {
        if (propertyInfo.GetIndexParameters().Length == 0)
        {
            dictionary.Add(propertyInfo.Name, propertyInfo.GetValue(o, null));
        }
    }

    return dictionary;
}

和Html Helper扩展：

/// <summary>
/// When viewData is null, we just return null.  Otherwise, we
///     convert the viewData collection to a ViewDataDictionary
/// </summary>
/// <param name="htmlHelper">HtmlHelper provided by view</param>
/// <param name="viewData">Anonymous view data object</param>
/// <returns></returns>
public static ViewDataDictionary vd(this HtmlHelper htmlHelper, object viewData)
{
    if (viewData == null) return null;

    IDictionary<string, object> dict = viewData.ToDictionary();

    //We build the ViewDataDictionary from scratch, because the
    //  object parameter constructor for ViewDataDictionary doesn't
    //  seem to work...
    ViewDataDictionary vd = new ViewDataDictionary();
    foreach (var item in dict)
    {
        vd[item.Key] = item.Value;
    }

    return vd;
}

使用剃刀文件：

@Html.Partial("~/Some/Path.cshtml", Model, Html.vd(new { SomeKey = SomeObj }))

初始化语法：new ViewDataDictionary {{“Name”，“Value”}}

2 个答案: