c# 写 webservice接口

//返回值为一组数据[WebMethod]public Boolean ValiLogin(string username, string password){        SqlConnection sqlconnection = new SqlConnection(ConnectionString);        sqlconnection.Open();        string cmdstring = "select password from [user] where username= " + "'" + username"'";  //sql语句        SqlCommand cmd= new SqlComnand(cmdString, sqlconnection);        string pass = (string)cmd.ExecuteScalar();                //定义变量存储数据        sqlconnection.Close();        if( (pass.Trim() != password.Trim())  || pass.Trim() == null) // Trim去多余空格            return false;        else return true;}//返回值为多组数据[WebMethod]protected DataSet tip_details(string username){        SqlConnection sqlconnection = new SqlConnection(ConnectionString);        sqlconnection.Open();        string cmdstring = "select title,details,id,time from [tip] ";        SqlDataAdapter sqlAdapteruser = new SqlDataAdapter(cmdstring, sqlconnection);        DataSet ds = new DataSet();        sqlAdapteruser.Fill(ds, "tip");        sqlconnection.Close();        return ds;}[WebMethod]public DataSet send_tips(string username)               //环保小贴士{        DataSet ds = new DataSet();        ds = tip_details(username);        return ds;}//计数：string cmdcount = "select count(username) from [user] where username=" + "'" + username + "'";        SqlCommand cmdd = new SqlCommand(cmdcount, sqlconnection);        int cc = (int)cmdd.ExecuteScalar();//查找 string cmdString = "select password from [user] where username=" + "'" + username + "'";        SqlCommand cmd = new SqlCommand(cmdString, sqlconnection);        string pas = (string)cmd.ExecuteScalar();//插入string insertString = "INSERT INTO [user] (username,password,sex,age,home,destination, telephone) values(" + "'" + username + "','" + password + "','" + sex + "','" +  age + "','" + home + "','" + destination + "','" + telephone + "')";            SqlCommand insert_cmd = new SqlCommand(insertString, sqlconnection);            insert_cmd.ExecuteNonQuery();//更新string updateString = "UPDATE [user] SET username=" + "'" + username + "',password=" +  "'" + password + "',sex=" + "'" + sex + "',age=" + "'" + age + "',home=" + "'" + home + "',destination=" + "'" + destination +  "',telephone=" + "'" + telephone + "'where username=" + "'" + username + "'";        SqlCommand update_cmd = new SqlCommand(updateString, sqlconnection);        update_cmd.ExecuteNonQuery();//删除 string cmdString = "delete from [order] where username=" + "'" + username + "'";        SqlCommand cmd = new SqlCommand(cmdString, sqlconnection);        cmd.ExecuteNonQuery();