使用ADO.net将数据导出到Excel并提供下载

public string DataTableToExcel(DataTable dt,string excelPath)
        {
            if(dt == null)
            {
                return "DataTable不能为空";
            }

            int rows = dt.Rows.Count;
            int cols = dt.Columns.Count;
            StringBuilder sb;
            string connString;

            if(rows == 0)
            {
                return "没有数据";
            }

            sb = new StringBuilder();
            connString = string.Format(ConnectionString,excelPath);

            //生成创建表的脚本
            sb.Append("CREATE TABLE ");
            sb.Append(dt.TableName + " ( ");

            for(int i=0;i<cols;i++)
            {
                if(i < cols - 1)
                    sb.Append(string.Format("{0} varchar,",dt.Columns[i].ColumnName));
                else
                    sb.Append(string.Format("{0} varchar)",dt.Columns[i].ColumnName));
            }

            using(OleDbConnection objConn = new OleDbConnection(connString))
            {
                OleDbCommand objCmd = new OleDbCommand();
                objCmd.Connection = objConn;

                objCmd.CommandText = sb.ToString();

                try
                {
                    objConn.Open();
                    objCmd.ExecuteNonQuery();
                }
                catch(Exception e)
                {
                    return "在Excel中创建表失败，错误信息：" + e.Message;
                }

                生成插入数据脚本#region 生成插入数据脚本
                sb.Remove(0,sb.Length);
                sb.Append("INSERT INTO ");
                sb.Append(dt.TableName + " ( ");

                for(int i=0;i<cols;i++)
                {
                    if(i < cols - 1)
                        sb.Append(dt.Columns[i].ColumnName + ",");
                    else
                        sb.Append(dt.Columns[i].ColumnName + ") values (");
                }

                for(int i=0;i<cols;i++)
                {
                    if(i < cols - 1)
                        sb.Append("@" + dt.Columns[i].ColumnName + ",");
                    else
                        sb.Append("@" + dt.Columns[i].ColumnName + ")");
                }
                #endregion

                //建立插入动作的Command
                objCmd.CommandText = sb.ToString();
                OleDbParameterCollection param = objCmd.Parameters;

                for(int i=0;i<cols;i++)
                {
                    param.Add(new OleDbParameter("@" + dt.Columns[i].ColumnName, OleDbType.VarChar));
                }

                //遍历DataTable将数据插入新建的Excel文件中
                foreach (DataRow row in dt.Rows)
                {   
                    for (int i=0; i<param.Count; i++)
                    {
                        param[i].Value = row[i];
                    }

                    objCmd.ExecuteNonQuery();
                }

                return "数据已成功导入Excel";
            }//end using
        }