Re: dictionary/list help needed - C# Discussion Boards

yoni.kess6-Oct-13 5:20

6-Oct-13 5:20

sorry
didnt notice it cut the code in the middle.

<pre>private void button3_Click(object sender, EventArgs e)
        {


            #region testing new code from web

            // this is a new code from the web

            Dictionary<string, List<LatLongPair>> LatLongCollectionByName = new Dictionary<string, List<LatLongPair>>();

            List<LatLongPair> lst = null;
            LatLongPair lPair = null;
            string matchHandle = string.Empty;

            for (int i = 0; i < LayersGrid.Rows.Count; i++)
            {
                if (LayersGrid.Rows[i].Cells[1].Value.ToString() == matchHandle)
                {
                    lPair.Lat = Convert.ToDouble(LayersGrid.Rows[i].Cells[3].Value);
                    lPair.Lon = Convert.ToDouble(LayersGrid.Rows[i].Cells[2].Value);
                    lst.Add(lPair);
                }
                else
                {
                    matchHandle = LayersGrid.Rows[i].Cells[1].Value.ToString();
                    lPair = new LatLongPair();
                    lPair.Lat = Convert.ToDouble(LayersGrid.Rows[i].Cells[3].Value);
                    lPair.Lon = Convert.ToDouble(LayersGrid.Rows[i].Cells[2].Value);

                    lst = new List<LatLongPair>();
                    lst.Add(lPair);

                        LatLongCollectionByName.Add(matchHandle, lst);

                }

                foreach (KeyValuePair<string, List<LatLongPair>> item in LatLongCollectionByName)
                {
                    Console.WriteLine("\n For name : " + item.Key + ", lat/long vaues are:\n");

                    foreach (LatLongPair lp in item.Value)
                    {
                        Console.Write("\t" + lp.Lat + ",\t" + lp.Lon + " | ");
                    }
                }

Richard MacCutchan6-Oct-13 5:45

6-Oct-13 5:45

LatLongCollectionByName.Add(matchHandle, lst);

According to the data you have shown, your matchHandle has either the value AZ1 or AZ2, so you can only add 1 entry of each name, since the Dictionary class does not allow duplicate keys.

Veni, vidi, abiit domum

yoni.kess6-Oct-13 5:51

6-Oct-13 5:51

so should i remove the dictionary and work only with the list?

Richard MacCutchan6-Oct-13 6:22

6-Oct-13 6:22

It all depends on what you are trying to do. You could use a list or one of the other members of the collection classes. It is best to look at the documentation[^] and then decide which class is most useful to you.

Veni, vidi, abiit domum

yoni.kess6-Oct-13 10:10

6-Oct-13 10:10

hi i am trying to collect all the lat and longs for each AZ.
then once all of them are collected to write them to a kml/text file.

since i am not much familiar with all the classes can you please advise.

thanks

Richard MacCutchan6-Oct-13 20:44

6-Oct-13 20:44

yoni.kess wrote:
since i am not much familiar with all the classes can you please advise.

As I said in my previous comment, it is really dependent on how you want to handle the data. You will have to go and read the documentation for yourself to decide which class offers what you want, whether it is a simple list or one of the more specialized classes. You may also like to consider whether you need a collection at all, or can just write the data direct to your file.

Veni, vidi, abiit domum

BillWoodruff6-Oct-13 16:58

BillWoodruff

6-Oct-13 16:58

Your question would be much more understandable if you put the code for button3_Click that you disclosed to Richard MacCutchan in your original post, and edited the code so only the possible problem area is shown.

If you have a field in your db that is guaranteed unique per row that you can use as a key, then using a Dictionary makes sense ... but, in this case, it appears you don't.

I'd start by modeling data structures from "inside to outside," from "atoms," to "molecules."

So, I'd define an "atomic class" that would hold only the necessary data for a single ship position measurement:

public class Position
{
    public bool IsDay  { get; private set; }
    public double Latitude  { get; private set; }
    public double Longitude  { get; private set; }

    public Position(bool isDay, double latitude, double longitude)
    {
        IsDay = isDay;
        Latitude = latitude;
        Longitude = longitude;
    }

    public override string ToString()
    {
        return
            "Time: "
            + (IsDay ? "Day " : "Night ")
            + " Latitude: " + Latitude.ToString()
            + " Longitude: " + Longitude.ToString();
    }
}

I'd then move on to the question of what my final goal is here: clearly each ship is going to have a collection of instances of Position:

internal class ShipPositionList : List<Position>
{
    public override string ToString()
    {
        string s = "";

        foreach (Position pos in this)
        {
            s += pos.ToString() + Environment.NewLine;
        }

        return s;
    }
}

And, finally, I'd consider what the data structure for the outermost object is:

public class Ship
{
    public string ShipName { get; private set; }

    internal ShipPositionList PositionList { get; private set; }

    public Ship(string shipName)
    {
        ShipName = shipName;

        PositionList = new ShipPositionList();
    }

    public void AddPosition(bool isDay, double lati, double longi)
    {
        PositionList.Add(new Position(isDay, lati, longi));
    }

    public override string ToString()
    {
        return
            ShipName
            + Environment.NewLine
            + PositionList.ToString();
    }
}

At this point, I might well start wondering why I am writing out such an elaborate multi-class model, and start coding lean-and-mean Smile | :)

Google CEO, Erich Schmidt: "I keep asking for a product called Serendipity. This product would have access to everything ever written or recorded, know everything the user ever worked on and saved to his or her personal hard drive, and know a whole lot about the user's tastes, friends and predilections." 2004, USA Today interview

yoni.kess6-Oct-13 21:39

6-Oct-13 21:39

Hi BillWoodruff

thanks for the detailed answer, but now i am even more confused D'Oh! | :doh:

i would have uploaded the project and the db if i only had were too. Smile | :)

small question: can i use one of the coordindated (for example: longitude) as a unique key and then use the dictionary?

thanks

Entity Framework: Primary key violation

BillWoodruff7-Oct-13 0:39

BillWoodruff

7-Oct-13 0:39

Hi Yoni.Kess,

I don't think you need to post any more code in order to solve your challenge Smile | :)

If you get the object-structure right, you can make it serializable into XML; if you've got the XML, you can, if necessary, transform it into KML with an XSLT. I'm not familiar with KML, but I would guess that there's probably good tools available to create it. My impression from looking at your data is that it's simple, and there's nothing there that's recursive, and that you can easily create your own structured output in whatever form with your own simple serializer.

A .NET Dictionary (a collection of KeyValuePairs) must have a unique key for each KeyValuePair: if you are absolutely sure that you'll never have two longitude values that are the same, yes, you can use them as keys. But, what is it that makes you think a dictionary is the right thing in this case ?

fyi: the standard .NET XML serializer cannot handle writing a Dictionary to XML: [^]. I have read that the .NET DataContractSerializer can serialize a Dictionary, but I have not tried this: [^], [^].

Being more confused is not necessarily a bad thing in learning to program, although it may not feel comfortable to be confused. Of course, that's no excuse, if my response confused you !

The goal I had in responding to you was to "point you to" thinking about the "big picture" in your current challenge: what you are really modeling. Thinking in terms of "atoms to molecules to compounds" ... or the reverse ... is just one metaphor for OOP modeling.

There's a lot I can't tell from eye-balling your data: it may be the case that what you really need is to break out the data by Day/Night ... since it appears written that way in the KML fragment you show. Knowing more details is not necessary, however.

I believe if you are clear about what your final goal is, then the design of the data structures you really need will "fall-out" organically: that's a very idealistic statement. In the real-world, it often doesn't work that way: we get "immersed" in the data, and observe patterns of organization in the data, reach conclusions about what variation is in the data, and how that may constrain our solution, and from that we get ideas about how to structure and optimize the data structures we'll create to contain the data.

good luck, Bill

Lutosław6-Oct-13 2:55

Lutosław

6-Oct-13 2:55

I try to add an object to a database, but I get an exception
Code:

DataModelContainer cont = new DataModelContainer();

(...)

cont.AddToStudentSet(cont.StudentSet.CreateObject());
cont.SaveChanges();

After running the code twice, I get:
Exception:
AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges.

The Id of Student has an AutoIncrement set to TRUE in the database. On the first run a single Student record is created with Id 0. Later, no data is saved to the table at all.
The reason of why is it happening seems to be obvious, but it should work anyway.
Any help appreciated

Greetings - Jacek

modified 6-Oct-13 9:04am.

Re: Entity Framework: Primary key violation

Dave Kreskowiak6-Oct-13 6:28

Dave Kreskowiak

6-Oct-13 6:28

Well, since you already have a student record with an Id of 0, you can't add another one. ID's should not start with 0.

A guide to posting questions on CodeProject[^]

Dave Kreskowiak

Re: Entity Framework: Primary key violation

Lutosław6-Oct-13 9:50

Lutosław

6-Oct-13 9:50

The scenario was:
1. I had designed tables with an inheritance relationship.
2. Decided that it was not a good idea
3. Removed an inheritance relationship
4. Added required IDs to the tables and set IsIdentity to true.
5. Forgot to set an identity property to "Identity".

Well...

Greetings - Jacek

update ConnectionString in App.config

Jassim Rahma6-Oct-13 0:03

Jassim Rahma

6-Oct-13 0:03

Hi,

I am using the following code in my Form_Load to read the ConnectionString elements from my WinForm C# application.

sql_connection = new MySqlConnection(ConfigurationManager.ConnectionStrings["SQLdb"].ConnectionString);
            
MySql.Data.MySqlClient.MySqlConnectionStringBuilder builder = new MySqlConnectionStringBuilder();
builder.ConnectionString = sql_connection.ConnectionString;

string server = builder.Server;
string port = builder.Port.ToString();
string user = builder.UserID;
string password = builder.Password;
string database = builder.Database;
string timeout = builder.ConnectionTimeout.ToString();
            
txtServer.Text = server;            
txtPort.Text = port;            
txtUserID.Text = user;
txtPassword.Text = password;
txtDatabase.Text = database;
txtTimeOut.Text = timeout;

I want to know how can get this back once changed by user and save it into the App.config's ConnectionString when user Clicks Save button?

Technology News @ www.JassimRahma.com

Re: update ConnectionString in App.config

OriginalGriff6-Oct-13 0:10

OriginalGriff

6-Oct-13 0:10

See here: Saving Connection Strings to app.config[^]

The only instant messaging I do involves my middle finger.

Simple cross threading question

ve3tru5-Oct-13 17:55

ve3tru

5-Oct-13 17:55

I have a working program that I want to add a little code to
Being a novice, ok beginner programer, I could use a little help.
Not sure the best way to do this, start another thread and cross thread, or can I do this in the one thread.
tnx

My thread code is like this

public static void Method_8()
        {
            while (method_state_6 && method_state_7  == true)
            {
                flooddrain.Write(false);
                Thread.Sleep(1 * HourMs);
                flooddrain.Write(true);
                Thread.Sleep(1 * HourMs);
         // At this point I want it to do x only once a day 
            }
        }

Abhinav S5-Oct-13 19:00

Abhinav S

5-Oct-13 19:00

I don't see the need for another thread.
Change the logic here - maybe make your code more flexible by making HoursMS 24.

But unless there are other concerns you should not be going for another thread.

Apps - Color Analyzer | Arctic | XKCD | Sound Meter | Speed Dial

ve3tru6-Oct-13 16:03

ve3tru

6-Oct-13 16:03

Well your right it should be done all in one thread.
some thing like this using a for loop a sleep and god knows what else Im really lost here.

for (int i = 0; i < 0; i++)
{
    Thread.Sleep(1 * DayMs);


}

Dave Kreskowiak6-Oct-13 4:24

Dave Kreskowiak

6-Oct-13 4:24

Ummm, do WHAT in another thread??

Also, your variable and method names suck. What in the Hell is "Method_8" supposed to do?? The name doesn't describe it's function at all. "Method_state_6"?? "Method_state_7"?? What do those represent??

Read up on the concept of "self documenting code".

A guide to posting questions on CodeProject[^]

Dave Kreskowiak

Richard MacCutchan6-Oct-13 5:04

Re: get pixel color on image

6-Oct-13 5:04

ve3tru wrote:
// At this point I want it to do x only once a day

Then forget about threads, and certainly forget about using Thread.Sleep for long periods like this. Write your app such that it does all that is necessary in one go, and use the Windows scheduler to run it at the times you need.

Veni, vidi, abiit domum

get pixel color on image

Member 102255295-Oct-13 4:51

Member 10225529

5-Oct-13 4:51

Hello,i want a code which retrieve the color from an image.where image is in fix format and x-y co-ordinate also...i want a read pixel and find the color of that pixel not by mouse positioning by only co-ordinates.plzzzzzzzzz Confused | :confused:

BillWoodruff5-Oct-13 7:22

BillWoodruff

5-Oct-13 7:22

What have you tried so far ? How many bits per pixel in the images: 1,4,8,16,24,32 ? Show us some code.

Re: get pixel color on image

Richard MacCutchan5-Oct-13 20:51