C#动态调用泛型类、泛型方法

在制作一个批量序列化工具时遇到了如下问题，在此记录一下，仅供参考。

主程序加载另一个程序集，将其中的所有类取出，然后对这些类分别调用泛型类或泛型方法。控制台程序解决方案如下：

• Main工程：提供Worker类进行数据操作，XMLTool<T>泛型类将数据集序列化为.xml文档，RootCollection<T>类封装数据集
  • Worker类

  　　     提供成员方法void DoWork<T>()、List<T> GetList<T>()、静态成员方法StaticDoWork<T>()，代码如下：

  

   1 public class Worker
   2     {
   3         public Worker()
   4         {
   5         }
   6 
   7         public void DoWork<T>()
   8         {
   9             Type t = typeof(T);
  10             Console.WriteLine("Get Class: {0}", t.Name);
  11             PropertyInfo[] properties = t.GetProperties();
  12             foreach (PropertyInfo property in properties)
  13             {
  14                 Console.WriteLine("\tproperty.Name: " + property.Name + "\tproperty.MemberType: " + property.PropertyType);
  15             }
  16         }
  17 
  18         public static void StaticDoWork<T>()
  19         {
  20             Type t = typeof(T);
  21             Console.WriteLine("Get Class: {0}", t.Name);
  22             PropertyInfo[] properties = t.GetProperties();
  23             foreach (PropertyInfo property in properties)
  24             {
  25                 Console.WriteLine("\tproperty.Name: " + property.Name + "\tproperty.MemberType: " + property.PropertyType);
  26             }
  27         }
  28 
  29         public List<T> GetList<T>()
  30         {
  31             Console.WriteLine("Generate List for [{0}]", typeof(T).Name);
  32             return new List<T>() 
  33             { 
  34                 Activator.CreateInstance<T>(), 
  35                 Activator.CreateInstance<T>() 
  36             };
  37         }
  38     }

  
• XMLTool<T>类
  

   1publicclass XMLTool<T>
   2     {
   3publicstaticvoid XmlSerialize_Save(List<T> needSerializedList, string xmlDirPath, string xmlFileName)
   4         {
   5             RootCollection<T> collection = new RootCollection<T>();
   6             collection.ItemList = needSerializedList;
   7if (!Directory.Exists(xmlDirPath))
   8                 Directory.CreateDirectory(xmlDirPath);
   9using (System.IO.FileStream stream = new System.IO.FileStream(xmlFileName, System.IO.FileMode.Create))
  10             {
  11                 System.Xml.Serialization.XmlSerializer serializer = new System.Xml.Serialization.XmlSerializer(collection.GetType());
  12                 serializer.Serialize(stream, collection);
  13             }
  14         }
  15     }

  
• RootCollection<T>类：
  

   1     [Serializable]
   2     public class RootCollection<T>
   3     {
   4         public RootCollection()
   5         {
   6             itemList = new List<T>();
   7         }
   8 
   9         private List<T> itemList;
  10 
  11         public List<T> ItemList
  12         {
  13             get { return itemList; }
  14             set { itemList = value; }
  15         }
  16     }

  
• MockClassLib工程：提供BaseEntity、Apple、Cat和Person类
• BaseEntity类：抽象类，负责初始化类成员
  

   1     public abstract class BaseEntity
   2     {
   3         public BaseEntity()
   4         {
   5             InitiaWithNull();
   6         }
   7
   8         private void InitiaWithNull()
   9         {
  10             Type type = this.GetType();
  11             PropertyInfo[] properties = type.GetProperties();
  12             string[] PropNames = new string[properties.Length];
  13             Dictionary<string, PropertyInfo> PropNameToInfo = new Dictionary<string, PropertyInfo>();
  14             for (int i = 0; i < properties.Length; i++)
  15             {
  16                 PropNames[i] = properties[i].Name;
  17                 PropNameToInfo.Add(PropNames[i], properties[i]);
  18             }
  19
  20             foreach (string propname in PropNames)
  21             {
  22                 string proptype = PropNameToInfo[propname].PropertyType.Name;
  23
  24                 object value = null;
  25                 if (NullValue.Keys.Contains(proptype))
  26                     value = NullValue[proptype];
  27
  28                 type.GetProperty(propname).SetValue(this, value, null);
  29             }
  30         }
  31
  32         private static readonly Dictionary<string, object> NullValue = new Dictionary<string, object>() 
  33             { 
  34                 { "String", String.Empty }, 
  35                 { "DateTime", DateTime.MinValue},
  36                 { "Decimal", Decimal.MinValue}
  37             };
  38     }

  
• Apple、Cat和Person类：测试类，继承于BaseEntity
  

   1     public class Apple : BaseEntity
   2     {
   3        public string Color { get; set; }
   4     }
   5
   6     public class Cat : BaseEntity
   7     {
   8        public string Type { get; set; }
   9     }
  10
  11     public class Person : BaseEntity
  12     {
  13        public int ID { get; set; }
  14        public string Name { get; set; }
  15     }

  

Main工程的Program的Main方法中，一般情况下，调用Worker的泛型方法来处理测试类的话，可以写为：

Worker worker = new Worker();

worker.DoWork<Apple>();

worker.DoWork<Cat>();

worker.DoWork<Person>();

但是，如果MockClassLib中需要处理的类型非常多时，这样显示调用必然是不灵活的，应当怎样向泛型方法DoWork<T>()的尖括号中动态传入类型呢？

考虑代码：

            //Load assembly
            Assembly mockAssembly = Assembly.LoadFrom("MockClassLibrary.dll");
            Type[] typeArray = mockAssembly.GetTypes();

            //Create instance of Worker          
            Worker worker = new Worker();
            foreach(Type curType in typeArray)
            {
                  worker.DoWork<curType>();   //Error
            }

可以看到，Type类型的实例是无法直接传入泛型方法的尖括号中的，T要求显式指明类型名。

下面通过反射方式来获取泛型方法，并创建特定类型的泛型方法。

• 对于非静态方法：public void DoWork<T>()

对于非静态方法，调用MethodInfo.Invoke(object, object[])时，第一个参数需要指明泛型方法的所有者（即这里创建的worker对象），第二个参数为泛

型方法的参数列表，DoWork<T>()没有输入参数，所以设为null

//Create an instance of Worker
Worker worker = new Worker();       

//Get type of Worker
Type workerType = typeof(Worker);

 //Get Generic Method
MethodInfo doWorkMethod = workerType.GetMethod("DoWork");

//Invoke DoWork<T> with different Type
foreach (Type curType in typeArray)
{
    if (curType.IsClass && !curType.IsAbstract)//Filter BaseEntity
    {
        MethodInfo curMethod = doWorkMethod.MakeGenericMethod(curType);
        curMethod.Invoke(worker, null);//Member method，use instance
    }
}

• 对于静态方法：public static void StaticDoWork<T>()

不同于非静态方法，这里直接反射的类静态方法，所以Invoke()的第一个参数设为null

//Get type of Worker
Worker worker = new Worker();

//Get Generic Method
MethodInfo staticDoWorkMethod = workerType.GetMethod("StaticDoWork");

//Invoke StaticDoWork<T>
foreach (Type curType in typeArray)
{
    if (curType.IsClass && !curType.IsAbstract)
    {
        MethodInfo curMethod = staticDoWorkMethod.MakeGenericMethod(curType);
        curMethod.Invoke(null, null);//Static method
    }
}

• 对于有返回值的非静态方法：public List<T> GetList()

如同动态调用DoWork<T>()方法一样，只是在处理返回值时，可以使用下面的方法

1 IList tempList = (IList)curMethod.Invoke(worker, null);
2 //Or
3 IEnumerable tempList = (IEnumerable)curMethod.Invoke(worker, null);

• 对于泛型类：XMLTool<T>

下面要使用泛型类XMLTool<T>的静态方法public static void XmlSerialize_Save(List<T> list, string dirPath, string fileName)方法。

首先应通过反射构造出指定类型的泛型类XMLTool<T>，再反射出其中的XmlSerialize_Save方法并使用。

 1 //Use Generic Class
 2 Type xmlToolType = typeof(XMLTool<>).MakeGenericType(curType);
 3 
 4 //Get method
 5 MethodInfo saveMethod = xmlToolType.GetMethod("XmlSerialize_Save");
 6 
 7 //Invoke
 8 saveMethod.Invoke
 9 (
10     null, //Static method
11     new object[] { resultList, @"c:\", @"c:\Test_" + curType.Name + ".xml" }

12 );

Program-->Main()方法的全部代码：

 1 namespace RetrieveUnknownClass
 2 {
 3     class Program
 4     {
 5         static void Main(string[] args)
 6         {
 7             //Load assembly
 8             Assembly mockAssembly = Assembly.LoadFrom("MockClassLibrary.dll");
 9             Type[] typeArray = mockAssembly.GetTypes();
10 
11             //Create instance of Worker          
12             Type workerType = typeof(Worker);
13             Worker worker = new Worker();
14 
15             #region Member method
16 
17             Console.WriteLine(">>>>>>>>>Use Generic Method：");
18             MethodInfo doWorkMethod = workerType.GetMethod("DoWork");
19 
20             //Invoke DoWork<T>
21             foreach (Type curType in typeArray)
22             {
23                 if (curType.IsClass && !curType.IsAbstract)
24                 {
25                     MethodInfo curMethod = doWorkMethod.MakeGenericMethod(curType);
26                     curMethod.Invoke(worker, null);//Member method，use instance
27                 }
28             }
29 
30             #endregion
31 
32             #region Static method
33 
34             Console.WriteLine("\r\n>>>>>>>>>Use Static Generic Method：");
35             MethodInfo staticDoWorkMethod = workerType.GetMethod("StaticDoWork");
36 
37             //Invoke StaticDoWork<T>
38             foreach (Type curType in typeArray)
39             {
40                 if (curType.IsClass && !curType.IsAbstract)
41                 {
42                     MethodInfo curMethod = staticDoWorkMethod.MakeGenericMethod(curType);
43                     curMethod.Invoke(null, null);//Static method
44                 }
45             }
46 
47             #endregion
48 
49             #region Get A List & Serialize It to Xml File With Generic 
50 
51             Console.WriteLine("\r\n>>>>>>>>>Get List By Generic Method：");
52             MethodInfo getListMethod = workerType.GetMethod("GetList");
53 
54             foreach (Type curType in typeArray)
55             {
56                 if (curType.IsClass && !curType.IsAbstract)
57                 {
58                     MethodInfo curMethod = getListMethod.MakeGenericMethod(curType);
59                     //Generate List
60                     IList resultList = (IList)curMethod.Invoke(worker, null);
61                     //Show List
62                     ShowList(resultList);
63                     //Use Generic Class
64                     Type xmlToolType = typeof(XMLTool<>).MakeGenericType(curType);
65                     MethodInfo saveMethod = xmlToolType.GetMethod("XmlSerialize_Save");
66 
67                     saveMethod.Invoke
68                         (
69                             null, //Static method
70                             new object[] { resultList, @"c:\", @"c:\Test_" + curType.Name + ".xml" }
71                         );
72                 }
73             }
74             
75             Console.WriteLine("Serialization Completed...\r\n");
76             #endregion
77         }
78 
79         public static void ShowList(IList list)
80         {
81             Console.WriteLine("Type of list: {0}\r\nCount of current list: {1}\r\nType of item in list: {2}\r\n", 
82                 list.GetType(), 
83                 list.Count, 
84                 list[0].GetType());
85         }
86     }
87 }