C# 通过反射初探ORM框架的实现原理(详解)

通过全限定名来获取 Type tp = Type.GetType("TJCommon.Dao.Deriver");
通过类来获取 Type tp = typeof(Int)

// 获取类的初始化构造信息
 ConstructorInfo ct = tp.GetConstructor(System.Type.EmptyTypes);
// 调用不带参数的构造器
T newObj = (T)ct.Invoke(null);

//定义参数类型数组
 Type[] tps = new Type[2];
 tps[0] = typeof(int);
 tps[1] = typeof(string);
 //获取类的初始化参数信息
 ConstructorInfo ct2 = tp.GetConstructor(tps);
 //定义参数数组
 object[] obj = new object[2];
 obj[0] = (object)100;
 obj[1] = (object)"Param Example";
 //调用带参数的构造器
 ExampleClass Ex2 = (ExampleClass)ct2.Invoke(obj);

// 获取到所有公共字段
FieldInfo[] arr = t.GetFields(); 
// 给指定的字段赋值 需要传递进来一个对象 newObj
f.SetValue(newObj, r[name]); 

public static T dataToObj(String str)
 {
  String strSql = str;
  DataSet ds = SqlCompose.ExecuteSqlQuery(strSql);
  Type t = typeof(T);
  DataRow r = ds.Tables[0].Rows[0]; // 找到一行
  FieldInfo[] arr = t.GetFields(); // 返回所有公共字段(public)
  ConstructorInfo ct = t.GetConstructor(System.Type.EmptyTypes);
  T newObj = (T)ct.Invoke(null);
  if (r != null)
  {
  foreach (FieldInfo f in arr)// 遍历所有字段
  {
   string name = f.Name;
   Type type2 = f.FieldType;
   if (r[name].GetType() != typeof(DBNull))
   {
   string typeName = f.FieldType.Name;
   f.SetValue(newObj, r[name]);
   }
  }
  }
  else
  {
  newObj = default(T);
  }
  ds.Tables.Clear();
  return newObj;
 }

public static List<T> dataToList(String str)
  {
   List<T> list = new List<T>();
   String strSql = str;
   DataSet ds = SqlCompose.ExecuteSqlQuery(strSql);
   Type t = typeof(T);
   FieldInfo[] arr = t.GetFields(); // 返回所有公共字段(public)
   ConstructorInfo ct = t.GetConstructor(System.Type.EmptyTypes);
   foreach (DataRow dr in ds.Tables[0].Rows)
   {
    T newObj = (T)ct.Invoke(null);
    foreach (FieldInfo f in arr)// 遍历所有字段
    {
     string name = f.Name;
     Type type2 = f.FieldType;
     string typeName = f.FieldType.Name;
     if (dr[name].GetType() != typeof(DBNull))
     {
      f.SetValue(newObj, dr[name]);
     }
    }
    list.Add(newObj);
   }
   ds.Tables.Clear();
   return list;
  }

public static void inserByBean(string tableName, T target)
 {
  StringBuilder sql = new StringBuilder(); // 拼接的sql
  sql.Append("insert into "+tableName+"(");
  Type t = target.GetType();
  PropertyInfo[] ps = t.GetProperties();
  for (int i = 0; i < ps.Length; i++)
  {
   object obj = ps[i].GetValue(target, null);
   if (obj != null)
   {
    string name = ps[i].Name;
    if (i != ps.Length - 1)
    {
     sql.Append(" " + name + ",");
    }
    else
    {
     sql.Append(" " + name + "");
    }
   }
  }
  sql.Append(") values(");

  for (int i = 0; i < ps.Length; i++)
  {
   object obj = ps[i].GetValue(target, null);
   if (obj != null)
   {
    if (i != ps.Length - 1)
    {
     if (ps[i].PropertyType == typeof(string) || ps[i].PropertyType == typeof(DateTime))
     {
      sql.Append("'" + obj + "',");
     }
     else {
      sql.Append("" + obj + ",");
     }
    }
    else
    {
     if (ps[i].PropertyType == typeof(string) || ps[i].PropertyType == typeof(DateTime))
     {
      sql.Append("'" + obj + "')");
     }
     else
     {
      sql.Append("" + obj + ")");
     }
    }
   }
  }
  string resultSql = sql.ToString();
  SqlCompose.ExecuteSqlNonQuery(resultSql);
 }