在C＃中将oledbdatareader转换为dbdatareader [英] convert oledbdatareader to dbdatareader in C#

问题描述

如何在C＃中动态地将System.Data.OleDb.OleDbDataReader转换为System.Data.Common.DbDataReader

 public T GetProjectCodes< t> （字符串Args）
 {
 string strProjects =; 
 
 string QryAllProject =select * from tbl_Project_Details; 
 
 if（Args ==S）
 {
 strProjects = MyTest.GetRecordString（gcnPROJECT，QryAllProject，*，\ n）; 
 return（T）Convert.ChangeType（strProjects，typeof（T））; 
} 
 else 
 {
 DbDataReader Dr = null; 
 Dr = MyTest.GetDataReader（gcnPROJECT，QryAllProject）; //此函数返回Dbdatareader 
 
 // return（T）Convert.ChangeType（Dr，typeof（T））; 
 // return（T）Convert.ChangeType（Dr，typeof（Dr））; 
 
 return（T）Convert.ChangeType（Dr，typeof（T））; 
 
} 
 
 // return（T）strProjects; 
} 
 
 public static DbDataReader GetDataReader（DbConnection myConnection，string strQry）
 {
 DbDataReader ObjmyReader0 = null; 
 DbDataReader ObjmyReader = null; 
 
 
 string RetVal = string.Empty; 
 DbCommand myCommand = null; 
 myCommand =（DbCommand）myConnection.CreateCommand（）; 
 // myCommand.CommandText =SELECT * FROM Dept; 
 myCommand.CommandText = strQry; 
 if（myConnection.State == ConnectionState.Closed || myConnection.State == ConnectionState.Broken）{
 myConnection.Open（）; 
} 
 
尝试
 {
 if（ObjmyReader！= null）
 {
 if（ObjmyReader.IsClosed == false）
 {
 ObjmyReader.Close（）; 
} 
} 
 
 ObjmyReader =（DbDataReader）myCommand.ExecuteReader（System.Data.CommandBehavior.CloseConnection）; 
 
} 
 catch（Exception rdExc）
 {
 if（（ObjmyReader！= null）&&（ObjmyReader.IsClosed == false））
 {
 ObjmyReader.Close（）; 
 ObjmyReader =（DbDataReader）myCommand.ExecuteReader（）; 
} 
} 
最后
 {
 myCommand.Dispose（）; 
 ObjmyReader0 = ObjmyReader; 
 
 // ObjmyReader.Close（）; 
} 
 
返回ObjmyReader0; 
 // return（DbDataReader）Convert.ChangeType（ObjmyReader0，typeof（DbDataReader））; 
 ObjmyReader0.Dispose（）; 
} 

请检查并指导我...

谢谢

vilas

解决方案

你为什么要那样做？ OleDbDataReader 继承自 DbDataReader 类（参见 MSDN [ ^ ]），因此您可以直接退货，不需要任何转换 。

Hi,

how to convert System.Data.OleDb.OleDbDataReader to System.Data.Common.DbDataReader
dynamically in C#

public T GetProjectCodes<t> (string Args) 
        {
           string strProjects = "";
           
            string QryAllProject ="select * from tbl_Project_Details";

            if (Args == "S")
            {
                strProjects = MyTest.GetRecordString(gcnPROJECT, QryAllProject, "*", "\n");
                return (T)Convert.ChangeType(strProjects, typeof(T));
            }
            else
            {
                DbDataReader Dr = null;
                Dr = MyTest.GetDataReader(gcnPROJECT, QryAllProject);// this function returns Dbdatareader 
                
                //return (T)Convert.ChangeType(Dr, typeof(T));
                //return (T)Convert.ChangeType(Dr, typeof(Dr));

                return (T)Convert.ChangeType(Dr, typeof(T));               

            }           
            
         // return (T) strProjects;
        }

  public static DbDataReader GetDataReader(DbConnection myConnection, string strQry)
        {
            DbDataReader ObjmyReader0 = null;
            DbDataReader ObjmyReader = null;


            string RetVal = string.Empty;
            DbCommand myCommand = null;
             myCommand = (DbCommand)myConnection.CreateCommand();
            // myCommand.CommandText = "SELECT * FROM Dept";
            myCommand.CommandText = strQry;
            if (myConnection.State == ConnectionState.Closed || myConnection.State == ConnectionState.Broken) {
                myConnection.Open();
            }

            try
            {
                if (ObjmyReader != null)
                {
                    if (ObjmyReader.IsClosed == false) 
                    {
                        ObjmyReader.Close();
                    }
                }

                ObjmyReader = (DbDataReader)myCommand.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
              
            }
            catch (Exception rdExc)
            {
                if ((ObjmyReader != null) && (ObjmyReader.IsClosed == false))
                {
                    ObjmyReader.Close();
                    ObjmyReader = (DbDataReader)myCommand.ExecuteReader();
                }
            }
            finally
            {
                myCommand.Dispose();
                ObjmyReader0 = ObjmyReader;
               
               // ObjmyReader.Close();
            }

            return ObjmyReader0;
            //return (DbDataReader)Convert.ChangeType(ObjmyReader0, typeof(DbDataReader));
            ObjmyReader0.Dispose();
        }

Please check and guide me...
thanks
vilas

解决方案

Why would you want to do that? The OleDbDataReader inherits from DbDataReader class (see MSDN[^]) , hence you may return it directly, without any ''conversion''.

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