我正在将Excel文件导入SQLServer数据库。该代码工作正常，但是我当前正在做的方式是删除（清除表）表数据。

         string ssqltable = "tStudent";
          string myexceldataquery = "select id,student,rollno,course from [sheet1$]";
        try
        {
            string sexcelconnectionstring = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source =" + excelfilepath + "; Extended Properties=\"Excel 12.0; HDR=Yes; IMEX=2\"";
            string ssqlconnectionstring = "Data Source=DELL\\SQLSERVER1;Trusted_Connection=True;DATABASE=Test;CONNECTION RESET=FALSE";

            SqlConnection sqlconn = new SqlConnection(ssqlconnectionstring);
            SqlCommand sqlcmd = new SqlCommand(@"MERGE tStudent AS target
                              USING (select ID, STUDENT , ROLLNO from @source)  as source
                                ON (source.ID = target.ID)
                              WHEN MATCHED THEN
                              UPDATE SET Student = source.Student,
                                         ROLLNO = source.ROLLNO
                              WHEN NOT MATCHED THEN
                              INSERT (ID, STUDENT , ROLLNO)
                              VALUES (source.id, source.Student, source.RollNo);", sqlconn);
          ******************************************
            SqlParameter param = new SqlParameter();
            sqlcmd.Parameters.AddWithValue("@source", dr);
            param.SqlDbType = SqlDbType.Structured;
            param.TypeName = "dbo.tStudent";
          ******************************************
            sqlconn.Open();
            sqlcmd.ExecuteNonQuery();
            sqlconn.Close();

            //series of commands to bulk copy data from the excel file into our sql table
            OleDbConnection oledbconn = new OleDbConnection(sexcelconnectionstring);
            OleDbCommand oledbcmd = new OleDbCommand(myexceldataquery, oledbconn);

            oledbconn.Open();
            OleDbDataReader dr = oledbcmd.ExecuteReader();
            SqlBulkCopy bulkcopy = new SqlBulkCopy(ssqlconnectionstring);
            bulkcopy.DestinationTableName = ssqltable;

            bulkcopy.WriteToServer(dr);
            while (dr.Read())
            {
                //bulkcopy.WriteToServer(dr);
            }
            oledbconn.Close();
            Console.WriteLine(".xlsx file imported succssessfully into database.", bulkcopy.NotifyAfter);
        }

请参阅 * 部分。我已经在Sqlparameters中分配了OleDb DataRreaderdr，但是稍后将在代码中声明它。请指导我如何构造代码。

示例将不胜感激。