模糊查询时预编译报错,该怎么处理

模糊查询时预编译报错
string checkResult = rbtTiaojian.SelectedValue;
  p=txtcontent.Text.Trim();
  switch (checkResult)
  {
  case "1": strWhere = "u_sitNo=@p"; break;
  case "2": strWhere = "u_Enterprise like %@p%"; break;
  }
  System.Data.SqlClient.SqlParameter parameters = new System.Data.SqlClient.SqlParameter("@p", p);
  string strSql = "select u_id,u_Enterprise,u_UserName,u_EnterpriseType,u_Phone, u_RealName,u_Mobile, u_RegisterTime from Ec_UserInfo where " + strWhere;

  DataTable dt = DbHelperSQL.Query(strSql, parameters).Tables[0];
  ResultView.DataSource = dt;
  ResultView.DataBind();

  运行上面代码，checkResult为1时可以通过；checkResult为2时就会报错呢？求解答！！！

[解决办法]
case "2": strWhere = "u_Enterprise like '%'+@p+'%'"; break;