Re: Retrieving Data From Form2 - C# Discussion Boards

AmbiguousName12-Dec-11 23:13

AmbiguousName

12-Dec-11 23:13

Actually it does not have the button OK, it has the button Select. So I dont know how your solution us going to map here. Any guidance in this regard will be appreciated.

I actually have meaningful names for my forms but to keep the question simple, I said them Form1 and Form2 Smile | :)

Pete O'Hanlon12-Dec-11 23:35

Pete O'Hanlon

12-Dec-11 23:35

It doesn't matter what the text says - all you need to do is set its DialogResult to OK.

Forgive your enemies - it messes with their heads

"Mind bleach! Send me mind bleach!" - Nagy Vilmos

My blog | My articles | MoXAML PowerToys | Mole 2010 - debugging made easier - my favourite utility

Subin Mavunkal12-Dec-11 23:52

Subin Mavunkal

12-Dec-11 23:52

In teclick event of the grid , create a new instance of form1 with an overloaded constructor of Form1.make DataClass as the parameter , then Show form from there.Done

Pete O'Hanlon13-Dec-11 0:14

Pete O'Hanlon

13-Dec-11 0:14

So now he has two form1 instances running. I don't think that's the effect he's after.

Forgive your enemies - it messes with their heads

"Mind bleach! Send me mind bleach!" - Nagy Vilmos

My blog | My articles | MoXAML PowerToys | Mole 2010 - debugging made easier - my favourite utility

DaveyM6913-Dec-11 1:04

DaveyM69

13-Dec-11 1:04

There are two ways to do this, either by public/internal properties in Form2 or passing an instance of a custom class derived from EventArgs. Either will require some kind of signalling to Form1 that the data is ready.

As previously mentioned, if Form1 shows Form2 via ShowDialog() then you can expose a property in Form2, set the DialogResult of Form2 to DialogResult.OK and check for that as a result of the ShowDialog() call, accessing the property.

This same procedure can also be done by subscribing to Form2s FormClosing event, although the dialog result is a better alternative as you have information relating to the success/failure of user interaction.

Alternatively, Form2 can raise a custom event subscribed to by Form1. If using this method (the one I prefer) then you can pass a custom event args class instance along with the event that contains only the relevant data - nice and clean and no need to expose properties in Form2 to the whole world.

Dave

Binging is like googling, it just feels dirtier.
Please take your VB.NET out of our nice case sensitive forum.
Astonish us. Be exceptional. (Pete O'Hanlon)

BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)

Subin Mavunkal13-Dec-11 2:03

Subin Mavunkal

13-Dec-11 2:03

Yes , He can write a custom event. Smile | :)

BillWoodruff13-Dec-11 12:14

BillWoodruff

13-Dec-11 12:14

This type of question: communication of data or events between two forms, is among the most commonly asked and answered type of question on QA in CP.

The critical piece of information to have, imho, in considering a solution is to know under what circumstances Form1 and Form2 (to use your form names) are created:

1. Keeping a run-time created reference: if Form1 creates Form2, or Form2 creates Form1: at the moment of creating it: the Form that creates has a reference to the other Form it has created.

That reference can be stored, and, then, all public properties (and methods, or anything else that's public) can be accessed by the creating Form.

In terms of the question of knowing when Form2 is closed: if Form1 creates Form2: at the moment its created and assigned to some variable in Form1: you can immediately subscribe to Form2's Closing or Closed events, and add an EventHandler defined in Form1.

Here's a code example that demonstrates both the above. First, this is implemented in Form2:

public DataGridView Form2DataGridView { get; set;  }

private void Form2_Load(object sender, EventArgs e)
{
    Form2DataGridView = dataGridView1;
}

And, then, this is implemented in Form1:

// inside Form1
private Form2 NewForm2
//
private void Form1_Load(object sender, EventArgs e)
{
    NewForm2 = new Form2();
    NewForm2.Closed += new EventHandler(NewForm2_Closed);

    NewForm2.Form2DataGridView.SelectionChanged += new EventHandler(Form2DataGridView_SelectionChanged);
}

private void NewForm2_Closed(object sender, EventArgs e)
{
    // your code goes here
}

public void Form2DataGridView_SelectionChanged(object sender, EventArgs e)
{
    // your code goes here
}

1.a. The special case of using 'ShowDialog' for presentation of a Form is a special case of this: imho, nothing in the OP suggests 'ShowDialog' is being used. But, you have some good answers here, now, based on the assumption you use 'ShowDialog.' But, please note that you can create one, or both Forms, once, and keep a reference ... if one Form creates the other ... just as described above. Just re-use the reference to the instance of the Form in the ShowDialog mode.

1.b. The special case where both instances of Form1 and Form2 are created by some other entity: well, you can adapt what's suggested in points #1~2. ... edit ... This also is the case, imho, where you may explore the use of Interfaces to pass instances of Forms that implement the Interface cast to the Interface so you effectively limit what is exposed by the passed object. S. A. Kryukov often advocates this method in his QA answers: for example:[^]. ... edit ...

2. Injection: This usually means that one Form has a "vacant" public property, and another Form, when creating the second form with the property sets the value of the public property.

So, Form1 could have a public property of type DataGridView, and in Form2's Load event, Form2 could set the value of that property to the instance's DataGridView: but look at what is implied by that: Form2 must have access to the instance of Form1 ! To me this is "dog wag tail" implemenation: where this makes sense is if Form1 contains the DataGridView, and Form1 creates Form2, and Form2 needs access to the DataGridView on Form1. Then, this is easy because Form1 has access to the instance of Form2 at the moment it creates it.

2.a. I have to admit I have a strong bias against the idea of injecting a reference to a whole Class, or Form, into another Form or Class because I believe this is a violation of the principle of "separation of concerns."

Does Form1 really need access to everything public in Form2 ? If the answer is "yes," then I'd go for code as shown in the example above. But, if the answer is "no," then I'd modify Form1 code as shown above:

// inside Form1
private DataGridView F2DataGridView;
//
private void Form1_Load(object sender, EventArgs e)
{
    // edit : corrected omission of 'Form2 here ...
    Form2 NewForm2 = new Form2();
    NewForm2.Closed += new EventHandler(NewForm2_Closed);
  
    F2DataGridView = NewForm2.Form2DataGridView;

    F2DataGridView .SelectionChanged += new EventHandler(F2DataGridView _SelectionChanged);
}

private void NewForm2_Closed(object sender, EventArgs e)
{
    // your code goes here
}

public void F2DataGridView _SelectionChanged(object sender, EventArgs e)
{
    // your code goes here
}

The difference in code may seem trivial: but, this implementation means that the only "exposed" object in Form2's instance within Form1's instance is the DataGridView on Form2, because the variable NewForm2 exists only in the scope of Form1's Load EventHandler.

2. Use of some "external" class to expose objects to other classes: You can create a public static class that maintains public Properties which can be set in each Form's 'Load, or 'Shown, EventHandlers, and then are visible to any Form in the same NameSpace. You could even set EventHandlers within that static class.

3. Raising events: This is probably the strategy most appropriate for the scenario you have described, particularly since it enables multiple subscribers to consumers (creators and users) of the instance(s) of Form2.

I've omitted code examples for #2~3, believing they are easy to find here on CP, within articles, tip/tricks, and QA, but if you have further questions, just ask.

"For no man lives in the external truth among salts and acids, but in the warm, phantasmagoric chamber of his brain, with the painted windows and the storied wall." Robert Louis Stevenson

modified 14-Dec-11 6:42am.

Seriously? user-defined conversions to or from an interface are not allowed

BobJanova13-Dec-11 23:11

BobJanova

13-Dec-11 23:11

For any sort of complex application, both forms should be looking at some non-UI data model. So all Form2 should have to 'pass back' to Form1 is a selected index or an identifier for the model object that corresponds to the selected row.

Without knowing what the UI context of these two forms is (does Form2 spawn Form1 as an editor? are both forms top level forms? etc) it's hard to be more detailed than that. But the key point is that the data grid on Form2 should be a view on an IList<YourDataModelClass> (well, possibly, a BindingList or a BindingSource on a List) and the various controls on Form1 should be a view on the properties of a YourDataModelClass. You can achieve this with data binding or manually setting properties, and you'll probably want either the model class or a view-model to implement change notification (INotifyPropertyChanged) so that when you update things from Form1, Form2 also refreshes its view. If you're using WPF then you can just use Binding attributes in the XAML.

As Bill says this is a pretty common question in Q&A so you might want to search there and have a look at some of the recommended answers.

Alaric_12-Dec-11 9:16

Alaric_

12-Dec-11 9:16

the relevant code

public static explicit operator ExcelWorksheet(Worksheet worksheet)
{
    return new ExcelWorksheet(worksheet, 1,1);
}
public static explicit operator Worksheet(ExcelWorksheet worksheet)
{
    return worksheet._worksheet;
}

...I'm trying to introduce a cast from the Interop.Excel.Worksheet to our Biz.Custom.ExcelWorksheet so that I can prep the COM proxy outside of the existing process, and allow an explicit cast from a valid COM Worksheet to be accepted as the custom's structurally subtyped property.

I researched the error and found out that this did not make the prioritization list to be removed from C#4 but could not find a workaround.

Does anyone have the proper incantation that will allow me to cast from the COM object to my custom?

Being required to convert these to "FromWorksheet" and "ToWorksheet" methods seems *completely* asinine.

"I need build Skynet. Plz send code"

modified 13-Dec-11 10:57am.

Re: Seriously? user-defined conversions to or from an interface are not allowed

BobJanova14-Dec-11 5:09

BobJanova

14-Dec-11 5:09

This is by design, as shown by this quote from the C# spec: "User-defined conversions are not allowed to convert from or to interface-types. In particular, this restriction ensures that no user-defined transformations occur when converting to an interface-type, and that a conversion to an interface-type succeeds only if the object being converted actually implements the specified interface-type". (source[^]). I don't really understand why you can't cast from an interface, but there you have it.

Having something that looks like a cast that actually switches to a completely different COM service is probably a bad thing anyway, though. When the conversion is so simple I recommend you just use 'new ExcelWorksheet(...)' and 'worksheet._worksheet' inline (well okay that last one should probably use a read property not the field directly).

TCPClient and TCPListener

michaelgr112-Dec-11 2:38

michaelgr1

12-Dec-11 2:38

Hello,
I am writing a project which sends SQL query to server, it runs it and returns back to client the results using streaming.
The flow is sending query,clientIP and port the client is going to listen to using WCF. before sending the WCF, the client opens a listener on the chosen port, and waits for a networkStream from the server. this done in a seperate thread. meanwhile the client sends the WCF request (with query,client ip, client port) to server and it returns the results to the waiting client on the right port.
All this done in seperate thread so i can run several queries simultanesly from the same client. After i received the results i am trying to close the TcpListener and TcpClient opened in the client side (in the opened thread). But when the other thread running it throws exception: Unable to read data from the transport connection: A blocking operation was interrupted by a call to WSACancelBlockingCal.
If i don't close the listener and client it works fine.
So how can i close the TcpListener and TcpClient in the thread without causing problem to the second thread .
TcpListener and TcpClient are not static.

Code:
private void OpenListenerTask(int port,AutoResetEvent resetEvent)
{
try
{
NetworkStream getStream = StartListenerGetStream(port, resetEvent);
string localIp = Dns.GetHostAddresses(Dns.GetHostName())[0].ToString();
var networkReader = new Reader(getStream, localIp, _sendPort.Value, _query);
networkReader.Start();

}
catch (Exception e)
{
Console.WriteLine(e.GetBaseException().Message);
}
//close TcpClient & TcpListener after data/error received
_client.Close();
_listener.Stop();
}

private TcpClient _client;
private TcpListener _listener;
private NetworkStream StartListenerGetStream(int port,EventWaitHandle resetEvent)
{

var tcpListener = new TcpListener(port);
tcpListener.Start();
_listener = tcpListener;
//tcpListener.Server.Blocking = false;
resetEvent.Set();

var tcpClient = tcpListener.AcceptTcpClient();
_client = tcpClient;

return tcpClient.GetStream();
}

jschell12-Dec-11 8:32

jschell

12-Dec-11 8:32

michaelgr1 wrote:
i am trying to close the TcpListener and TcpClient opened in the client side

You can't close a TcpListener in the client. The client doesn't own nor have access to that.

michaelgr112-Dec-11 8:57

michaelgr1

12-Dec-11 8:57

yes,
but in my solution, probably i didn't explain it. The server sending the data and the client receives it. So the listener is opened in the client side

Addy Tas12-Dec-11 11:44

Addy Tas

12-Dec-11 11:44

I take it that your listener has nothing to do with the terminology in socket communication?
Why not use sender and receiver? That takes away the uncertainty of what issue you are really facing.

Cheers, AT

Cogito ergo sum

Writing a 6502 cross assembler in c#

jschell13-Dec-11 8:32

jschell

13-Dec-11 8:32

The "server" is the one that opens the listener.
The "client" is the one that connects with a client socket to the server (where the listener is.)

I don't care how you label your app(s).

And what I said holds. The client can't close the listener.
The client can close the client socket.
The server can close the client socket (the one it created based on a listener request.)

Derek Henderson12-Dec-11 0:27

Derek Henderson

12-Dec-11 0:27

This is my first post to discussion so please forgive any mistakes of protocol etc

I am looking to write a 6502 (and possibly later z80) cross assembler to run on the pc using c#. My question is not for code but rather for technique and approach. As I have not done this sort of project before I was wandering what techniques I should use to interpret a line of code. Bearing in mind I need to identify both the instruction and addressing mode.

I can of course actually do this already by either using regular expressions or simply string manipulation but I'd like to know how it's should be done. Other people must have spent years writing assemblers and languages and must know the best approach.

Hope that all makes sense. Discuss .............

Derek

Luc Pattyn12-Dec-11 1:05

Luc Pattyn

12-Dec-11 1:05

Let me first admit I'm not a big fan of Regex as they can be powerful, but also cryptic and slow. I do use them in some cases, e.g. I used a few for some of the web page parsing inside CP Vanity (see one of my articles).

I would not even consider using them while writing a compiler or cross-assembler (which I have done dozens of time, mostly in Fortran and later in C). BTW: the really fun part is writing a simulator to go with it.

I'd suggest you write methods (based on string manipulations) that check for and extract a label, a directive or instruction, a first operand, a second operand, etc.

FWIW: everything that can be done with Regex, can also be done without them. I see them as a language add-on, just like LINQ. You can use it if you want, you don't have to.

Smile | :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

Derek Henderson12-Dec-11 1:19

Derek Henderson

12-Dec-11 1:19

Thanks Luc, nice to have the view of someone who has actually done it.

Thanks

harold aptroot12-Dec-11 4:52

harold aptroot

12-Dec-11 4:52

I know one z80 assembler that is written using only string manipulation (not even regex).. it's a nice assembler to use, but the source is a bit of a mess.
Anyway, as usual when parsing some non-trivial, I would suggest using an actual parser. Depending on whether/which parser generator you use, things like "include" may be a little hacky.
But of course string manipulation works fine too.

Richard MacCutchan12-Dec-11 5:01

Richard MacCutchan

12-Dec-11 5:01

I have used Antlr[^] for a not dissimilar task in the past.

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Derek Henderson12-Dec-11 5:06

Derek Henderson

12-Dec-11 5:06

Thats not something i'd thought about, thats for this.

Derek