c# - 初始化器语法：new ViewDataDictionary { { "Name", "Value" } }

Question

我正在寻找一种将 ViewDataDictionary 传递给 ASP.NET MVC 中的局部视图的方法，我得到了这种语法：

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

我对这里的初始化语法有点困惑。谁能给我解释一下？

Answer 1

ViewDataDictionary实现IDictionary<string, object>。

IDictionary<string, object>本质上是一个集合KeyValuePair<string, object>。

您的ViewDataDictionary初始化程序（外大括号）包含另一组表示KeyValuePair<string, object>初始化程序的大括号。

这个答案解释了这可能的原因。

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

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

是相同的：

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

本质上，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;
}

还有一个 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;
}

从剃刀文件中用作：

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