C#反射 字符串转为实体类，并做为参数传入泛型方法中使用

工作中有这样一个需求，有N张不同的报表，每张报表对应一个数据源，统计数据采用内存方式，首先在内在里定义了数据源对应实体。统计条件用lamdba表达式式实现，通过工具对单元格进行定义。在实现过程中针对每一张表来写取数显示是很Low的了，取数条件定义都是规则的，统计实现就是一段C#代码，但是要针对不同的数据源也就是不同的List<Entity>，通过研究发现通过泛型和反射可以实现。

根据字符串获取实体类型

 private Type getEntity(string typeName)
 {
     var workPath = AppDomain.CurrentDomain.BaseDirectory;
     string[] files = Directory.GetFiles(workPath, "XXX.Utils.dll", SearchOption.TopDirectoryOnly);
     foreach (string file in files)
     {
         string ext = file.Substring(file.LastIndexOf("."));
         if (ext != ".dll") continue;
         try
         {
             Assembly asm = Assembly.LoadFile(file);
             Type[] allTypes = asm.GetTypes();
             foreach (Type t in allTypes)
             {
                 if (t.IsSubclassOf(typeof(XXDataRecord)))
                 {
                     if (t.Name.ToUpper().IsSame(typeName.ToUpper()))
                         return t;
                 }
             }
         }
         catch
         {
             return null;
         }
     }
     return null;
 }

泛型方法定义

 public XXDataMemory BuildDataMemoryPattern<T>(XXParams zb, string id) where T : XXDataRecord, new()

调用方法代码

 var obj = new GenerateDataHelper(_Param);
 Type myGenericClassType = obj.GetType();
 //MakeGenericMethod 设置泛型参数类型
 MethodInfo mi = myGenericClassType.GetMethod("BuildDataMemoryPattern").MakeGenericMethod(typeEntity);
 int count = ;
 //设置调用方法参数
 object[] invokeArgs = new object[] { zb, id, count };
 //调用
 var dt = (DataTable)mi.Invoke(obj, invokeArgs);
 //获取回返数据
 recordCount = (int)invokeArgs[];

下面是全部代码，具体功能实现略过

 public class UtilFetchHelper
 {
     //获取实体类型
     private Type getEntity(string typeName)
     {
         var workPath = AppDomain.CurrentDomain.BaseDirectory;
         string[] files = Directory.GetFiles(workPath, "XXX.Utils.dll", SearchOption.TopDirectoryOnly);
         foreach (string file in files)
         {
             string ext = file.Substring(file.LastIndexOf("."));
             if (ext != ".dll") continue;
             try
             {
                 Assembly asm = Assembly.LoadFile(file);
                 Type[] allTypes = asm.GetTypes();
                 foreach (Type t in allTypes)
                 {
                     if (t.IsSubclassOf(typeof(XXDataRecord)))
                     {
                         if (t.Name.ToUpper().IsSame(typeName.ToUpper()))
                             return t;
                     }
                 }
             }
             catch
             {
                 return null;
             }
         }
         return null;
     }

     public DataTable BuildDataMemoryPattern(XXParams zb, string id, out int recordCount)
     {
         //根据传入参数获取实体名称
         var entityName = GetDataSourceEntityName(zb);
         //获取实体类型
         Type typeEntity = getEntity(entityName);
         if (typeEntity == null)
             return  null;
         var obj = new GenerateDataHelper(_Param);
         Type myGenericClassType = obj.GetType();
         MethodInfo mi = myGenericClassType.GetMethod("BuildDataMemoryPattern").MakeGenericMethod(typeEntity);
         int count = ;
         object[] invokeArgs = new object[] { zb, id, count };
         var dt = (DataTable)mi.Invoke(obj, invokeArgs);
         //这里获取回返数据
         recordCount = (int)invokeArgs[];
         return dt;
     }
 }

 public class GenerateDataHelper
 {
     private List<XXDataRecord> _DataList;
     private List<XXDataRecord> DataList
     {
         set { _DataList = value; }
         get { return _DataList; }
     }    

     private List<T> GetDataSource<T>() where T : XXDataRecord, new()
     {
         var _DataList = new List<T>();
         var dt = DB.ExecuteDataTable("Select * From XX");
         for (int i = ; i < dt.Rows.Count; i++)
         {
             var dataEnt = new T();
             for (int j = ; j < dt.Columns.Count; j++)
             {
                 dataEnt[dt.Columns[j].ColumnName] = dt.Rows[i][j];
             }
             _DataList.Add(dataEnt);
         }
         return _DataList;
      }

     public XXDataMemory BuildDataMemoryPattern<T>(XXParams zb, string id) where T : XXDataRecord, new()
     {
         List<T> DataList = new List<T>();
         DataList = GetDataSource<T>();
         //以下是具体实现代码 针对DataList查询操作
     }
 }