IDataReader/DataTable扩展ToList 改进版，反射速度慢的惊人！

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IDataReader扩展ToList<T> 改进版

         // 最快 和直接循环差不多
         public   static  List < TResult >  ToList < TResult > ( this  IDataReader dr,  bool  isClose)  where  TResult :  class ,  new () {
            IDataReaderEntityBuilder < TResult >  eblist  =  IDataReaderEntityBuilder < TResult > .CreateBuilder(dr);
            List < TResult >  list  =   new  List < TResult > ();
             if  (dr  ==   null )  return  list;
             while  (dr.Read()) list.Add(eblist.Build(dr));
             if  (isClose) { dr.Close(); dr.Dispose(); dr  =   null ; }
             return  list;
        }
         public   static  List < TResult >  ToList < TResult > ( this  IDataReader dr)  where  TResult :  class ,  new () {
             return  dr.ToList < TResult > ( true );
        }

         // 也慢
         public   static  List < TResult >  ToList2 < TResult > ( this  IDataReader dr,  bool  isClose)  where  TResult :  class ,  new () {
            List < TResult >  oblist  =   new  List < TResult > ();
             if  (dr  ==   null )  return  oblist;

            List < string >  drColumns  =   new  List < string > ();
             int  len  =  dr.FieldCount;
             for  ( int  j  =   0 ; j  <  len; j ++ ) drColumns.Add(dr.GetName(j).Trim());
            
            List < PropertyInfo >  prlist  =   new  List < PropertyInfo > ();
            Type t  =   typeof (TResult);
            Array.ForEach < PropertyInfo > (t.GetPropertiesCache(), p  =>  {  if  (drColumns.IndexOf(p.Name)  !=   - 1 ) prlist.Add(p); });

             while  (dr.Read()) {
                TResult ob  =   new  TResult();
                prlist.ForEach(p  =>  {  if  (dr[p.Name]  !=  DBNull.Value) p.SetValue(ob, dr[p.Name],  null ); });
                oblist.Add(ob);
            }
             if  (isClose) { dr.Close(); dr.Dispose(); dr  =   null ; }
             return  oblist;
        }
         public   static  List < TResult >  ToList2 < TResult > ( this  IDataReader dr)  where  TResult :  class ,  new () {
             return  dr.ToList2 < TResult > ( true );
        }

         // 最慢
         public   static  List < TResult >  ToList3 < TResult > ( this  IDataReader dr,  bool  isClose)  where  TResult :  class ,  new () {
            List < TResult >  list  =   new  List < TResult > ();
             if  (dr  ==   null )  return  list;
             int  len  =  dr.FieldCount;

             while  (dr.Read()) {
                TResult info  =   new  TResult();
                 for  ( int  j  =   0 ; j  <  len; j ++ ) {
                     if  (dr[j]  ==   null   ||   string .IsNullOrEmpty(dr[j].ToString()))  continue ;
                    info.GetType().GetPropertyCache(dr.GetName(j).Trim()).SetValue(info, dr[j],  null );
                }
                list.Add(info);
            }
             if  (isClose) { dr.Close(); dr.Dispose(); dr  =   null ; }
             return  list;
        }
         public   static  List < TResult >  ToList3 < TResult > ( this  IDataReader dr)  where  TResult :  class ,  new () {
             return  dr.ToList3 < TResult > ( true );
        }

 

谢谢"幸运草"提供更快速的DataReader转实体LIST的代码.我将发在这里:

     public   class  IDataReaderEntityBuilder < Entity >  {
         private   static   readonly  MethodInfo getValueMethod  =
         typeof (IDataRecord).GetMethod( " get_Item " ,  new  Type[] {  typeof ( int ) });
         private   static   readonly  MethodInfo isDBNullMethod  =
             typeof (IDataRecord).GetMethod( " IsDBNull " ,  new  Type[] {  typeof ( int ) });
         private   delegate  Entity Load(IDataRecord dataRecord);

         private  Load handler;
         private  IDataReaderEntityBuilder() { }
         public  Entity Build(IDataRecord dataRecord) {
             return  handler(dataRecord);
        }
         public   static  IDataReaderEntityBuilder < Entity >  CreateBuilder(IDataRecord dataRecord) {
            IDataReaderEntityBuilder < Entity >  dynamicBuilder  =   new  IDataReaderEntityBuilder < Entity > ();
            DynamicMethod method  =   new  DynamicMethod( " DynamicCreateEntity " ,  typeof (Entity),
                     new  Type[] {  typeof (IDataRecord) },  typeof (Entity),  true );
            ILGenerator generator  =  method.GetILGenerator();
            LocalBuilder result  =  generator.DeclareLocal( typeof (Entity));
            generator.Emit(OpCodes.Newobj,  typeof (Entity).GetConstructor(Type.EmptyTypes));
            generator.Emit(OpCodes.Stloc, result);
             for  ( int  i  =   0 ; i  <  dataRecord.FieldCount; i ++ ) {
                PropertyInfo propertyInfo  =   typeof (Entity).GetProperty(dataRecord.GetName(i));
                Label endIfLabel  =  generator.DefineLabel();
                 if  (propertyInfo  !=   null   &&  propertyInfo.GetSetMethod()  !=   null ) {
                    generator.Emit(OpCodes.Ldarg_0);
                    generator.Emit(OpCodes.Ldc_I4, i);
                    generator.Emit(OpCodes.Callvirt, isDBNullMethod);
                    generator.Emit(OpCodes.Brtrue, endIfLabel);
                    generator.Emit(OpCodes.Ldloc, result);
                    generator.Emit(OpCodes.Ldarg_0);
                    generator.Emit(OpCodes.Ldc_I4, i);
                    generator.Emit(OpCodes.Callvirt, getValueMethod);
                    generator.Emit(OpCodes.Unbox_Any, dataRecord.GetFieldType(i));
                    generator.Emit(OpCodes.Callvirt, propertyInfo.GetSetMethod());
                    generator.MarkLabel(endIfLabel);
                }
            }
            generator.Emit(OpCodes.Ldloc, result);
            generator.Emit(OpCodes.Ret);
            dynamicBuilder.handler  =  (Load)method.CreateDelegate( typeof (Load));
             return  dynamicBuilder;
        }
    }

 

使用反射的同志们，请放泣使用反射方法转实体类LIST.

 

DataTable扩展ToList<T> 改进版

         // 最快和直接循环差不多
         public   static  List < TResult >  ToList < TResult > ( this  DataTable dt)  where  TResult :  class ,  new () {
            List < TResult >  list  =   new  List < TResult > ();
             if  (dt  ==   null )  return  list;
            DataTableEntityBuilder < TResult >  eblist  =  DataTableEntityBuilder < TResult > .CreateBuilder(dt.Rows[ 0 ]);
             foreach (DataRow info  in  dt.Rows) list.Add(eblist.Build(info));
            dt.Dispose(); dt  =   null ;
             return  list;
        }

         // 也慢
         public   static  List < TResult >  ToList2 < TResult > ( this  DataTable dt)  where  TResult :  class ,  new () {  
            List < PropertyInfo >  prlist  =   new  List < PropertyInfo > ();
            Type t  =   typeof (TResult);
            Array.ForEach < PropertyInfo > (t.GetPropertiesCache(), p  =>  {  if  (dt.Columns.IndexOf(p.Name)  !=   - 1 ) prlist.Add(p); });
            List < TResult >  oblist  =   new  List < TResult > ();

             foreach  (DataRow row  in  dt.Rows) {
                TResult ob  =   new  TResult();
                prlist.ForEach(p  =>  {  if  (row[p.Name]  !=  DBNull.Value) p.SetValue(ob, row[p.Name],  null ); });
                oblist.Add(ob);
            }
             return  oblist;
        }

         // 最慢
         public   static  List < TResult >  ToList3 < TResult > ( this  DataTable dt)  where  TResult :  class ,  new () {
            List < TResult >  list  =   new  List < TResult > ();
             if  (dt  ==   null )  return  list;
             int  len  =  dt.Rows.Count;

             for  ( int  i  =   0 ; i  <  len; i ++ ) {
                TResult info  =   new  TResult();
                 foreach  (DataColumn dc  in  dt.Rows[ 0 ].Table.Columns) {
                     if  (dt.Rows[i][dc.ColumnName]  ==   null   ||   string .IsNullOrEmpty(dt.Rows[i][dc.ColumnName].ToString()))  continue ;
                    info.GetType().GetPropertyCache(dc.ColumnName).SetValue(info, dt.Rows[i][dc.ColumnName],  null );
                }
                list.Add(info);
            }
            dt.Dispose(); dt  =   null ;
             return  list;
        }

     public   class  DataTableEntityBuilder < Entity >  {
         private   static   readonly  MethodInfo getValueMethod  =   typeof (DataRow).GetMethod( " get_Item " ,  new  Type[] {  typeof ( int ) });
         private   static   readonly  MethodInfo isDBNullMethod  =   typeof (DataRow).GetMethod( " IsNull " ,  new  Type[] {  typeof ( int ) });
         private   delegate  Entity Load(DataRow dataRecord);

         private  Load handler;
         private  DataTableEntityBuilder() { }

         public  Entity Build(DataRow dataRecord) {
             return  handler(dataRecord);
        }
         public   static  DataTableEntityBuilder < Entity >  CreateBuilder(DataRow dataRecord) {
            DataTableEntityBuilder < Entity >  dynamicBuilder  =   new  DataTableEntityBuilder < Entity > ();
            DynamicMethod method  =   new  DynamicMethod( " DynamicCreateEntity " ,  typeof (Entity),  new  Type[] {  typeof (DataRow) },  typeof (Entity),  true );
            ILGenerator generator  =  method.GetILGenerator();
            LocalBuilder result  =  generator.DeclareLocal( typeof (Entity));
            generator.Emit(OpCodes.Newobj,  typeof (Entity).GetConstructor(Type.EmptyTypes));
            generator.Emit(OpCodes.Stloc, result);

             for  ( int  i  =   0 ; i  <  dataRecord.ItemArray.Length; i ++ ) {
                PropertyInfo propertyInfo  =   typeof (Entity).GetProperty(dataRecord.Table.Columns[i].ColumnName);
                Label endIfLabel  =  generator.DefineLabel();
                 if  (propertyInfo  !=   null   &&  propertyInfo.GetSetMethod()  !=   null ) {
                    generator.Emit(OpCodes.Ldarg_0);
                    generator.Emit(OpCodes.Ldc_I4, i);
                    generator.Emit(OpCodes.Callvirt, isDBNullMethod);
                    generator.Emit(OpCodes.Brtrue, endIfLabel);
                    generator.Emit(OpCodes.Ldloc, result);
                    generator.Emit(OpCodes.Ldarg_0);
                    generator.Emit(OpCodes.Ldc_I4, i);
                    generator.Emit(OpCodes.Callvirt, getValueMethod);
                    generator.Emit(OpCodes.Unbox_Any, propertyInfo.PropertyType);
                    generator.Emit(OpCodes.Callvirt, propertyInfo.GetSetMethod());
                    generator.MarkLabel(endIfLabel);
                }
            }
            generator.Emit(OpCodes.Ldloc, result);
            generator.Emit(OpCodes.Ret);
            dynamicBuilder.handler  =  (Load)method.CreateDelegate( typeof (Load));
             return  dynamicBuilder;
        }
    }

 

 

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