如何从 C# 中的 arraylist 将数据插入数据库

Question

I have a class as 'Student'. I have done xml parse and then i recorded xml elements to arraylist using this class.Then i want to insert the elements from arraylist to database.How can i do this?

            int id=1;
            Arraylist arylist=new Arraylist();
            xmlparse.Load(Url);
            XmlNodeList nodes = xmlparse.SelectNodes("...");//Url nodes

            foreach (XmlNode item in nodes)
            {
                XmlNode innode = item.SelectSingleNode("name");

                string xml_name = innode != null ? innode.InnerText : "";

                innode = item.SelectSingleNode("parts");
                string xml_parts = innode != null ? innode.InnerText : "";

...

                arylist.Add(new Student(id, xml_name, xml_parts...));
                id++;

            }

I tried to something like this.But i couldnt do exactly.Is there anyone can u help me

   foreach (int i in arylist)
            {
                var mycommand = new OleDbCommand("insert into Student (name,parts) values (@name,@parts)", connection);
                mycommand.Parameters.AddWithValue("@name",i dont know what i should write here);
            }

Answer 1

Your code will need to look like:

using(mycommand = new OleDbCommand("insert into Student (name,parts) values (@name,@parts)", connection)){

  mycommand.Parameters.AddWithValue("@name","dummy name");
  mycommand.Parameters.AddWithValue("@parts","dummy part"); //assuming parts is a string - you haven't made any code to parse it

  foreach (object o in arylist)
  {
    Student s = (Student)o; //this isn't needed if you use a List<Student>..

    mycommand.Parameters["@name"].Value = s.Name; //or whatever your name property is
    mycommand.Parameters["@parts"].Value = s.Parts; //or whatever your parts property is

    mycommand.ExecuteNonQuery();
  }
}

We have all our students in an ArrayList (not the best choice; but everyone is stuck on telling you about that so I won't repeat their words) so we should:

• Create a command, with a connection (I assume you Open() ed it elsewhere). We do this in a using block so c# will clean up after us - always good to do with DB stuff. Remember to do the same with your connection
• Add some dummy parameters to the command - we'll put the real values in in a minute
• start looping over the arraylist, pulling out one student at a time
  • .. converting it from object to Student so it's easier to work with, and then
  • .. putting the values from the student in, and then
  • .. executing the query

Take a read of this, to guide your future coding: https://blogs.msmvps.com/jcoehoorn/blog/2014/05/12/can-we-stop-using-addwithvalue-already/

I don't personally take much issue with AddWithValue if it's used for parameters that are not in a WHERE clause but you should at least appreciate what it's doing and the trouble it can cause