Question

给出以下类和数据：

public class InnerExample
{
    public string Inner1 { get; set; }
}


public class Example
{
    public string Property1 { get; set; }
    public string Property2 { get; set; }
    public List<InnerExample> Inner { get; set; }
}

var a = new Example
{
    Property1 = "Foo",
    Property2 = "Bar",
    Inner = new List<InnerExample>
    {
      new InnerExample
      {
        Inner1 = "This is the value to change"
      }
   }
};

有没有办法通过路径访问最里面的数据？

有什么方法可以说......

a["Inner[0].Inner1"] = "New value"

在这种特殊情况下，我知道我永远不会访问不存在的密钥，因此我并不过分担心错误检查。

（很抱歉，如果以前曾经问过这个问题。我做过一些搜索，但很快就用掉了关键字试试。）

Answer 1

没有任何内置功能，但它可以做到（即使它不会是微不足道的。）

您想要的是在课程Example中添加indexer。在索引器内部，您必须将提供的“属性路径”解析为步骤，并使用reflection逐步解析目标属性。

例如，在将Inner[0].Inner1解析为三个不同的步骤（获取Inner，然后从该获取[0]，然后从该Inner1）解析后，您将拥有一个循环有点像这样：

// This works only with plain (non-indexed) properties, no error checking, etc.
object target = this;
PropertyInfo pi = null;
foreach (var step in steps)
{
    pi = target.GetType().GetProperty(step);
    target = pi.GetValue(target);
}

// And now you can either return target (on a get) or use pi.SetValue (on a set)

Answer 2

感谢你给我的基本建议，Jon，我提出了一个适合我案例的解决方案。

没有错误检查
您必须设置属性，而不是数组元素。

我确信有更有效的方法可以做到这一点......我远非反思专家。

/// <summary>
/// Take an extended key and walk through an object to update it.
/// </summary>
/// <param name="o">The object to update</param>
/// <param name="key">The key in the form of "NestedThing.List[2].key"</param>
/// <param name="value">The value to update to</param>
private static void UpdateModel(object o, string key, object value)
{
    // TODO:
    // Make the code more efficient.

    var target = o;
    PropertyInfo pi = null;

    // Split the key into bits.
    var steps = key.Split('.').ToList();

    // Don't walk all the way to the end
    // Save that for the last step.
    var lastStep = steps[steps.Count-1];
    steps.RemoveAt(steps.Count-1);

    // Step through the bits.
    foreach (var bit in steps)
    {
        var step = bit;

        string index = null;

        // Is this an indexed property?
        if (step.EndsWith("]"))
        {
            // Extract out the value of the index
            var end = step.IndexOf("[", System.StringComparison.Ordinal);
            index = step.Substring(end+1, step.Length - end - 2);

            // and trim 'step' back down to exclude it.  (List[5] becomes List)
            step = step.Substring(0, end);
        }

        // Get the new target.
        pi = target.GetType().GetProperty(step);
        target = pi.GetValue(target);

        // If the target had an index, find it now.
        if (index != null)
        {
            var idx = Convert.ToInt16(index);

            // The most generic way to handle it.
            var list = (IEnumerable) target;
            foreach (var e in list)
            {
                if (idx ==0)
                {
                    target = e;
                    break;
                }
                idx--;
            }
        }
    }

    // Now at the end we can apply the last step,
    // actually setting the new value.
    if (pi != null || steps.Count == 0)
    {
        pi = target.GetType().GetProperty(lastStep);
        pi.SetValue(target, value);
    }
}

按路径访问嵌套结构（即“Model.NestedModel.ListOfThings [1]”）

2 个答案: