Re: Mapping a class to a table that has two primary keys - C# Discussion Boards

Re: Virtual Drive in c#

Eddy Vluggen18-Jul-14 22:24

Eddy Vluggen

18-Jul-14 22:24

Like this[^].

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]

Re: Virtual Drive in c#

Dilan Shaminda19-Jul-14 0:05

Dilan Shaminda

19-Jul-14 0:05

You can use Dokan Libray for creating virtual drivers http://dokan-dev.net/en/[^]

Mapping a class to a table that has two primary keys

Member 128472117-Jul-14 17:32

Member 1284721

17-Jul-14 17:32

How can I map a class to a table that has two primary keys, I have a table called Region that has two primary keys, RegionID and DistrictID, here is my code: can someone tell me what I am missing? Thanks

Class Region
{
[Key, Display(Name = "RegionID")]
public int RegionID {get;set;}

[Key, Display(Name = "DistrictID")}
public int DistrictID {get;set;}

.....

}

Re: Mapping a class to a table that has two primary keys

PIEBALDconsult17-Jul-14 18:29

PIEBALDconsult

17-Jul-14 18:29

A table can't have two primary keys; do you mean that the key includes both columns?
And which framework/ORM are you using?

You'll never get very far if all you do is follow instructions.

Re: Mapping a class to a table that has two primary keys

Member 128472118-Jul-14 3:07

Member 1284721

18-Jul-14 3:07

Yes, it's a primary that has two columns, RegionID and DistrictID

Re: Mapping a class to a table that has two primary keys

Eddy Vluggen18-Jul-14 3:27

Eddy Vluggen

18-Jul-14 3:27

That's a compound primary key; RegionID and DistrictID aren't primary keys, they are foreign keys - if the combination uniquely identifies a record, then the combination of both fields is the primary key.

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]

Re: Mapping a class to a table that has two primary keys

Karen Mitchelle17-Jul-14 19:31

Karen Mitchelle

17-Jul-14 19:31

What? That can't be. A table has only one primary key.

Don't mind those people who say you're not HOT. At least you know you're COOL.
I'm not afraid of falling, I'm afraid of the sudden stop at the end of the fall! - Richard Andrew x64

Re: Mapping a class to a table that has two primary keys

Bernhard Hiller17-Jul-14 21:07

Bernhard Hiller

17-Jul-14 21:07

First we need to clarify what you mean with "two primary keys". Is it a rpimary key which consists of both "RegionID" and "DistrictID"? Or did you calculate an extra value from those data and make that your primary key?
Or is it actually one foreign key and one primary key?
Or something else?

Re: Mapping a class to a table that has two primary keys

Member 128472118-Jul-14 3:04

Member 1284721

18-Jul-14 3:04

Thanks for your reply, yes, it's a primary key which consitsts of both RegionID and DistrictID.

Re: Mapping a class to a table that has two primary keys

Rob Philpott18-Jul-14 4:27

Rob Philpott

18-Jul-14 4:27

a 'compound' primary key.

Regards,
Rob Philpott.

Re: Mapping a class to a table that has two primary keys

Member 128472118-Jul-14 4:37

Member 1284721

18-Jul-14 4:37

Thanks, can you provide a simple code? Thanks

public class Region
{

// what I should define here
public int RegionID {get;set;}

// then what I should define here
public int DistrictID {get;set;}
}

Re: Mapping a class to a table that has two primary keys

Rob Philpott18-Jul-14 4:49

Rob Philpott

18-Jul-14 4:49

You haven't stated what database you're using or whether you are using an ORM (which it looks like you are), and if so which one.

Personally I never use ORMs, so I can't advise I'm afraid.

Regards,
Rob Philpott.

Re: Mapping a class to a table that has two primary keys

Eddy Vluggen18-Jul-14 5:13

Eddy Vluggen

18-Jul-14 5:13

public class Region
{
    [Key, Column(Order = 0)]
    public int RegionId { get; set; }

    [Key, Column(Order = 1)]
    public int DistrictId { get; set; }
}

That is, assuming you're using EF; you still did not specify which mapper you are using. I'd also like to recommend an artificial key, and to decorate your compound key with a unique-constraint. Having a single attribute to identify a record makes life a bit easier when having to reference a specific record.

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]

Re: Mapping a class to a table that has two primary keys

Member 128472118-Jul-14 6:37

Member 1284721

18-Jul-14 6:37

Thank you very much, I am runnig into an error when using Order, I have the using System.ComponentModel.DataAnnotations.Schema and System.ComponentModel.DataAnnotations, I am using VS12, can you tell me what I am missing? Thanks again.

Re: Mapping a class to a table that has two primary keys

Eddy Vluggen18-Jul-14 6:46

Eddy Vluggen

18-Jul-14 6:46

What error?

It might help if you post the exception Smile | :)

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]

Re: Mapping a class to a table that has two primary keys

Member 128472118-Jul-14 7:20

Member 1284721

18-Jul-14 7:20

System.Data.Linq.Mapping.ColumnAttribute' does not contain a definition for 'Order'

Re: Mapping a class to a table that has two primary keys

Eddy Vluggen18-Jul-14 7:26

Eddy Vluggen

18-Jul-14 7:26

Like I said, I was assuming you're using the Entity Framework, but there's always MSDN[^] to help.

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]

Multiple cmd processes

Member 1095341617-Jul-14 3:55

Member 10953416

17-Jul-14 3:55

Hi all,

I use a certain command/process which i run in the command line. After it is started, it'll keep polling until i hit Ctrl-C. I use the command in multiple cmd windows (it's used for multiple directories).

Now i want to create a little C# program which is shown in the Windows toolbar where the user can create new processes of it (multiple), can manage to 'stop' (ctrl-c) a certain process, etc.

But somehow i cannot get this to work, especially the 'multiple' part. I cannot create multiple command windows with different commands, which i can manage afterwards (by ID or so).

I tried the solution of this thread: Starting cmd.exe in console application in different window.[^]

However, in that example you can only give 1 command - so the Ctrl-C cannot happen at a later stage.

Is this possible in C#? And if not, which language can do this?

Sorry for my poor english.

Re: Multiple cmd processes

OriginalGriff17-Jul-14 8:46

OriginalGriff

17-Jul-14 8:46

Since your application is starting the external processes, it's simple: all you have to do is keep a reference to teh Process object you used to start it, and then use SendKeys:

StartProcess("Notepad.exe");
    }

private Process notePad;

private void StartProcess(string p)
    {
    notePad = new Process();
    notePad.StartInfo.FileName = p;
    notePad.Start();
    }

[DllImport("User32.dll")]
static extern int SetForegroundWindow(IntPtr point);

private void butSendDataToNotepad_Click(object sender, EventArgs e)
    {
    IntPtr hWnd = notePad.MainWindowHandle;
    SetForegroundWindow(hWnd);
    SendKeys.SendWait(tbDataToSend.Text);
    }

Those who fail to learn history are doomed to repeat it. --- George Santayana (December 16, 1863 – September 26, 1952)
Those who fail to clear history are doomed to explain it. --- OriginalGriff (February 24, 1959 – ∞)

Re: Multiple cmd processes

Member 1095341618-Jul-14 8:56

Member 10953416

18-Jul-14 8:56

Thank you for your reply.

I tried your suggestion with a little test. So far it worked, i was able to create 2 separate cmd.exe processes and was able to send commands to it any time i wanted. However, the windows of the cmd.exe processes where all open, and got focus if it wrote a command in it. When i tried to hide the windows with this:

this.process.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;

It didn't work anymore. The problem is here i think that the combination of 'SetForegroundWindow' and'SendKeys' will need an active window - it simulates user input, so it needs an active window which isn't hidden to send keys to it.

Is there some way to hide it? The user must not be able to see the cmd.exe processes, it should all just run in the background.

What is state machine C# ?

Tridip Bhattacharjee17-Jul-14 2:32

Tridip Bhattacharjee

17-Jul-14 2:32

i do not anything about state machine. so anyone please briefly discuss in easy way what is state machine? in what kind of situation people think to develop or use any existing state machine. explain with example & scenario. thanks

tbhattacharjee

Re: What is state machine C# ?

OriginalGriff17-Jul-14 2:37

OriginalGriff

17-Jul-14 2:37

We do not do your homework: it is set for a reason. It is there so that you think about what you have been told, and try to understand it. It is also there so that your tutor can identify areas where you are weak, and focus more attention on remedial action.

Try it yourself, you may find it is not as difficult as you think!

In this case, a simple Google would find you all the answers: it found me this straight away.
A Simple State Machine[^]

Re: What is state machine C# ?

Pete O'Hanlon17-Jul-14 3:18

Pete O'Hanlon

17-Jul-14 3:18

I wouldn't bother. It's plain from earlier questions that this member doesn't bother with anything as boring as doing research.

Going Pass Limit of 64 bit Processor

computerpublic17-Jul-14 2:30

computerpublic

17-Jul-14 2:30

<pre>/*I am doing calculations and I am noticing that sometimes the arithmetic goes pass the limit of the 64 bit processor without me even realizing it. The number simple start calculating again from zero(0). Is there some sort of argument or exception that can notify the user when a calculation violates the limit of the processor and continue to calculate from zero(0) again.*/
 
using System;
using System.IO;
using System.Collections;
namespace check
{
    static class Program
    {
        static void Main(string[] args)
        {
            ulong increment = 2;
            for (ulong i = 0; i < 70; i++)
            {
                increment += i * increment;
                Console.WriteLine("{0}",increment);
            }

        }
    }
}

Re: Going Pass Limit of 64 bit Processor

Piotr Bagazja17-Jul-14 2:40

Piotr Bagazja

17-Jul-14 2:40

Use

checked

Like in example bellow:

try
{
    // The following line raises an exception because it is checked.
    z = checked(maxIntValue + 10);
}
catch (System.OverflowException e)
{
    // The following line displays information about the error.
    Console.WriteLine("CHECKED and CAUGHT:  " + e.ToString());
}

checked on msdn

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