迭代通过反射获得的字典

本文关键字：字典 反射 迭代 | 更新日期: 2023-09-27 18:15:20

我有这段代码，它应该递归地打印给定对象的所有属性和它们的内容。

static public void PrintProperties(object obj, int indent)
{
    if (obj == null) return;
    string indentString = new string(' ', indent);
    Type objType = obj.GetType();
    PropertyInfo[] properties = objType.GetProperties();
    foreach (PropertyInfo property in properties)
    {
        object propValue = property.GetValue(obj, null);
        if (property.PropertyType.Assembly == objType.Assembly && !property.PropertyType.IsEnum)
        {
            Console.WriteLine("{0}{1}:", indentString, property.Name);
            PrintProperties(propValue, indent + 2);
        }
        else
        {
            if (null != propValue)
            {
                Type t = propValue.GetType();
                //Console.WriteLine(":::::{0}:::::", propValue.GetType());
                bool isDict = t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Dictionary<,>);
                if (isDict)
                {
                    Type keyType = t.GetGenericArguments()[0];
                    Type valueType = t.GetGenericArguments()[1];
                    foreach (KeyValuePair<keyType, valueType> kvp in (Dictionary<keyType, valueType>)propValue)
                    {
                        Console.WriteLine(string.Format("Key = {0}, Value = {1}", kvp.Key, kvp.Value));
                    }
                }
            }
            Console.WriteLine("{0}{1}: {2}", indentString, property.Name, propValue);
        }
    }
}

还不能用于List和Dictionary，我现在正在研究Dictionary部分。

问题是，我提取了键和值的类型:

Type keyType = t.GetGenericArguments()[0];
Type valueType = t.GetGenericArguments()[1];

但是VS2013告诉我这一行有问题:

foreach (KeyValuePair<keyType, valueType> kvp in (Dictionary<keyType, valueType>)propValue)

它告诉我没有找到类型或命名空间KeyType和valueType。我错过了什么?

谢谢。

PS: .net 4.5.1

迭代通过反射获得的字典

基本就是你的keyType &valueType是Type类型的变量，在运行时已知，因此必须使用反射将propValue转换为适当的泛型字典。但是，为了向后兼容，您可以使用Dictionary<TKey,TValue>实现非泛型IDictionary接口的事实。

所以在你的特殊情况下，替换这个就足够了:

foreach (KeyValuePair<keyType, valueType> kvp in (Dictionary<keyType, valueType>)propValue)
与这个:

foreach (DictionaryEntry kvp in (IDictionary)propValue)

在调用泛型方法时，您必须提供实际的类型名称(或从您自己的方法定义中传递泛型类型参数)-而不是Type的实例。

正如decPL所指出的，您应该使用system . collections . dictionary。但是，您还应该更改isDict逻辑。System.Type.IsAssignableFrom允许你检查是否"指定类型的实例可以分配给当前类型实例"。下面是显示其行为的代码。

using System;
using System.Collections;
using System.Collections.Generic;
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Testing System.Type.IsAssignableFrom");
            var propValue = new Dictionary<string, string>() { { "hello", "world" } };
            var t = propValue.GetType();
            bool isDict = typeof(IDictionary).IsAssignableFrom(t);
            if (isDict)
            {
                foreach (DictionaryEntry kvp in (IDictionary)propValue)
                {
                    Console.WriteLine(string.Format("Key = {0}, Value = {1}", kvp.Key, kvp.Value));
                }
            }
            Console.ReadLine();
        }
    }
}

所以你的方法应该是这样的

static public void PrintProperties(object obj, int indent)
{
    if (obj == null) return;
    string indentString = new string(' ', indent);
    Type objType = obj.GetType();
    PropertyInfo[] properties = objType.GetProperties();
    foreach (PropertyInfo property in properties)
    {
        object propValue = property.GetValue(obj, null);
        if (property.PropertyType.Assembly == objType.Assembly && !property.PropertyType.IsEnum)
        {
            Console.WriteLine("{0}{1}:", indentString, property.Name);
            PrintProperties(propValue, indent + 2);
        }
        else
        {
            if (null != propValue)
            {
                Type t = propValue.GetType();
                //Console.WriteLine(":::::{0}:::::", propValue.GetType());
                bool isDict = typeof(IDictionary).IsAssignableFrom(t);
                if (isDict)
                {
                    foreach (DictionaryEntry kvp in (IDictionary)propValue)
                    {
                        Console.WriteLine(string.Format("Key = {0}, Value = {1}", kvp.Key, kvp.Value));
                    }
                }
            }
            Console.WriteLine("{0}{1}: {2}", indentString, property.Name, propValue);
        }
    }
}

但是，您也可以使用c# as操作符来执行此操作。as操作符将尝试对指定类型进行强制转换。如果不可能，则返回null。一些示例代码。

using System;
using System.Collections;
using System.Collections.Generic;
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Testing System.Type.IsAssignableFrom");
            var propValue = new Dictionary<string, string>() { { "hello", "world" } };
            IDictionary asDict = propValue as IDictionary;
            if (asDict != null)
            {
                foreach (DictionaryEntry kvp in (IDictionary)propValue)
                {
                    Console.WriteLine(string.Format("Key = {0}, Value = {1}", kvp.Key, kvp.Value));
                }
            }
            Console.ReadLine();
        }
    }
}

和你的方法。

static public void PrintProperties(object obj, int indent)
{
    if (obj == null) return;
    string indentString = new string(' ', indent);
    Type objType = obj.GetType();
    PropertyInfo[] properties = objType.GetProperties();
    foreach (PropertyInfo property in properties)
    {
        object propValue = property.GetValue(obj, null);
        if (property.PropertyType.Assembly == objType.Assembly && !property.PropertyType.IsEnum)
        {
            Console.WriteLine("{0}{1}:", indentString, property.Name);
            PrintProperties(propValue, indent + 2);
        }
        else
        {
            if (null != propValue)
            {
                var asDict = propValue as IDictionary;
                if (asDict != null)
                {
                    foreach (DictionaryEntry kvp in asDict)
                    {
                        Console.WriteLine(string.Format("Key = {0}, Value = {1}", kvp.Key, kvp.Value));
                    }
                }
            }
            Console.WriteLine("{0}{1}: {2}", indentString, property.Name, propValue);
        }
    }
}
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