C# Discussion Boards - CodeProject

Object property with different return types

Articus12-Jan-04 7:13

12-Jan-04 7:13

I have a control 'MyControl' with a property of type 'MyObject'. MyObject has a property 'MyField' that is a enum type. I want the type of enum to vary depending on a another property of MyObject called 'MyFieldType'. E.g. if MyFieldType = TypeA, MyField returns EnumA. See code below:

public enum FieldTypes
{
TypeA,
TypeB
}

public enum EnumA
{
Big,
Medium,
Small
}

public enum EnumB
{
Short,
Tall,
Squat,
Huge
}

[DefaultProperty("MyFieldType")]
public class MyObject
{
private FieldTypes m_MyFieldType;
private object m_MyField = 0;

public FieldTypes MyFieldType
{
get {return m_MyFieldType;}
set {m_MyFieldType = value;}
}

public object MyField
{
get
{
if (MyFieldType == FieldTypes.TypeA)
{
return (EnumA)m_MyField;
}
else
{
return (EnumB)m_MyField;
}
}
set
{
m_MyField = value;
}
}
}

My problem is that the MyField property is not editable via a dropdown list in the designer. It appears as a greyed-out (read only) string representation of the respective enum (EnumA or EnumB). I've tried writing a TypeConverter (inheriting from EnumConverter) but just ended up going round in circles.

Does anyone have an example of what I'm trying to do or point me in the right direction?

Thanks

Re: Object property with different return types

leppie12-Jan-04 8:16

leppie

12-Jan-04 8:16

It is because you are returning object. That said, if you return an object from an encapsulting class, and apply the ExpandableObjectConverter, you should be able to access the "real" properties.

leppie ::AllocCPArticle("Zee blog");
Seen on my Campus BBS: Linux is free...coz no-one wants to pay for it.

Re: Object property with different return types

Articus12-Jan-04 22:41

Articus

12-Jan-04 22:41

MyObject is already using the ExpandableObjectConverter that's not the problem. It's the MyField property. If I use an ExpandableObjectConverter for this property, the property becomes editable, but as a string not an enum. I think I need to use some kind of EnumConverter and dynamically specify the enum type, but I don't know how.

Re: Object property with different return types

leppie13-Jan-04 6:16

leppie

13-Jan-04 6:16

You wanna make a typeconvertor for the type and apply that. The key methods to override (implement) is SupportValues() and GetSupportedValuesCollection() (the method names are most likely wrong Poke tongue | ;-P

too lazy to look them up). This will automaticaly create an "enum" like convertor, do not implemeted any other methods.

leppie ::AllocCPArticle("Zee blog");
Seen on my Campus BBS: Linux is free...coz no-one wants to pay for it.

Refresh TreeView in Place

webdudeIA12-Jan-04 5:24

webdudeIA

12-Jan-04 5:24

What is the best way to update a treeview node in place?

I have a tree view that exposes the nodes to an XML editor. When the value of this node changes [in the XML editor], I' like to update the tree to show the new value.

Coding in the heartland

Re: Refresh TreeView in Place

Heath Stewart12-Jan-04 8:48

Heath Stewart

12-Jan-04 8:48

There is no direct binding support such as this (though you could add support). Instead, watch the XML fragment/file for changes and update the node text. There are so many ways of doing this, however, that it'd be difficult to list them all here.

You could, for example, watch for any changes in your editor (like for a multi-line TextBox handle the TextChanged event). When it changes, rebuild your tree from the XML information in the TextBox. To update just the node who's representation has changed in the XML fragment/file, it would be much more difficult. You could construct a path by recursing up the parent elements and pre-pending the text each time, using the TreeView.PathSeparator to separate each node. Then use that to find the node in the tree and update only that TreeNode. This would get increasingly difficult for added and removed nodes because you would also have to take state into account. Most implementations I've seen simply refresh the tree, which is apparent for larger XML hierarchies.

-----BEGIN GEEK CODE BLOCK-----
Version: 3.21
GCS/G/MU d- s: a- C++++ UL@ P++(+++) L+(--) E--- W+++ N++ o+ K? w++++ O- M(+) V? PS-- PE Y++ PGP++ t++@ 5 X+++ R+@ tv+ b(-)>b++ DI++++ D+ G e++>+++ h---* r+++ y+++
-----END GEEK CODE BLOCK-----

Re: Refresh TreeView in Place

webdudeIA12-Jan-04 10:17

webdudeIA

12-Jan-04 10:17

Thanks Heath.

Fortunately, for this application I won't have to worry about too many added or removed nodes.

I continued to play around with the functionality I was looking for. The combination of events that gives me the functionality I'm looking for is both KeyUp and Leave. But, I see that TextChanged would work just as well. Thanks.

I set a flag to manage the dirty state of my text box and this seems to work well even when I have a 6mb XML file loaded in the tree.

I was looking for the method that I use to update just a single node in place. As you said, "simply... refresh the tree". Thanks. That works fine.

Coding in the Heartland

Enumerations

Anonymous12-Jan-04 4:10

Anonymous

12-Jan-04 4:10

Hopefully one of you guys could help me with this query about enumerations.

Heres a simple enumeration :

public enum e {Val1=1, Val2=2 }

This allocates Val1 as int 1, Val2 as int 2 and so on, so if i do :

int x = (int) e.Val2;

x is given the value of 2

Now heres the thing, I want to allocate four int values, now I know this code isnt right but it gives an idea of the effect I am after :

public enum e {Val1="1,2,3,4", Val2="5,6,7,8"};

So if I use the following code :

int[] x = (int[])e.Val2

Which would populate the int array X with the values 5,6,7,8

Re: Enumerations

Colin Angus Mackay12-Jan-04 5:56

Colin Angus Mackay

12-Jan-04 5:56

Anonymous wrote:
public enum e {Val1="1,2,3,4", Val2="5,6,7,8"};

The reason this does not work is because enum is intrinsically an int.

Anonymous wrote:
int[] x = (int[])e.Val2

Even if e.Val2 returned a string this code would not work because it is not possible to directly convert a string to an array of ints.

An idea might be to set up an array of arrays that map to the enum:

public enum e{Val1 = 0, Val2=1}

// Maps to some array

int[] x = (int[])myArray[(int)e];

--Colin Mackay--

EuroCPian Spring 2004 Get Together[^]

Re: Enumerations

Niels Penneman12-Jan-04 5:58

Niels Penneman

12-Jan-04 5:58

That is absolutely not supported! No arrays, no strings, ... you'd get the following error:

Type byte, sbyte, short, ushort, int, uint, long, or ulong expected

Hmm however you can combine 2 int16s into an int32 and find the values by doing some bit manipulation (in a function you call to calculate the values based on the int32 of the enum) I think, but that is way too complicated...

Why would you want to do such thing anyway?

greetz Wink | ;-)

*Niels Penneman*

Software/Dev Site
Personal Site

Re: Enumerations

Heath Stewart12-Jan-04 8:38

Heath Stewart

12-Jan-04 8:38

As the two previous posts said, this isn't possible for the reasons they gave. You can, however, use read-only members in a class like so:

public sealed class Values
{
  private Values() {} // Prevent instantiation.
  static Values()
  {
    Val1 = new int[] {1, 2, 3, 4};
    Val2 = new int[] {5, 6, 7, 8};
  }
  public static int[] Val1;
  public static int[] Val2;
}

Unregister Server Activated Object ?

Stefan Troschuetz12-Jan-04 2:35

Stefan Troschuetz

12-Jan-04 2:35

I use remoting in my application, which proofed to be very useful but now i have a small problem.

In the server application the remote object is register as an available service in singleton mode.

RemotingConfiguration.RegisterWellKnownServiceType(
typeof(RemoteObject),
"Server",
WellKnownObjectMode.Singleton );

Now I'm searching a way to unregister it in the server application, so no remote calls from clients are processed?

Re: Unregister Server Activated Object ?

Heath Stewart12-Jan-04 3:57

Heath Stewart

12-Jan-04 3:57

If you use a configuration file to publish the types you want remoted, you can use the RemotingServices.Disconnect to stop the object from receiving further messages. See the documentation for that method for more information.

The only other way is to stop the AppDomain in which the WKO is registered. If you're using a Windows Service, you can stop the service both manually using the Services snap-in or the ServiceController class. If you're hosting this in another process, you could create a separate AppDomain and launch an executable that registers the WKO, then when you want to stop it unload the AppDomain using AppDomain.Unload.

One more way that wouldn't unregister the WKO but would keep it from processing requests (which I wouldn't recommend because clients will still see the published WKO) would be to put the interface in a shared library and the implementation of that on the server. Have an internal method that you can call that could do something like set a flag. In each of your interface implementation methods / properties, check that flag and either don't return anything or throw some sort of exception, like NotSupportedException or something. The first two methods are more complete, IMO.

Re: Unregister Server Activated Object ?

Stefan Troschuetz12-Jan-04 5:54

Stefan Troschuetz

12-Jan-04 5:54

Thanks for info!
I'm now using this code in my server application and it functions very well.

this.remoteObject = new RemoteObject();
System.Runtime.Remoting.RemotingServices.Marshal(this.remoteObject, "Server");

System.Runtime.Remoting.RemotingServices.Disconnect(this.remoteObject);

Could not load type.

Simon Wren12-Jan-04 1:16

Simon Wren

12-Jan-04 1:16

I have just finished creating a C# class library that has public classes available in it, when i include this lib in my test applications it works fine, but when i passed it to the division i wrote it for they complained it will not work. The error they get is as follows:

"An unhandled exception of type 'System.TypeLoadException" occurred in unknown module. Additional information: could not load type"

It then lists the class they are trying to access from my component.

They are adding a reference to an existing C# app, when they create a test app and add it the component works fine.

My question is what does this unhelpful error message mean and how can i fix it?

Any help would be great Smile | :)

Simon Wren
simon.wren@nesltd.co.uk
Senior Software Architect
National Energy Services Ltd
Visit Us: www.nesltd.co.uk Or: www.nher.co.uk

Re: Could not load type.

Heath Stewart12-Jan-04 2:38

Heath Stewart

12-Jan-04 2:38

A TypeLoadException can occur for many reasons. Since each Type is a fully-qualified class name (includes an optional namespace) in an assembly that has a version, culture, and public key token, any change to that assembly would cause an invalid type. For instance, if you compiled your app against version 1.0.0.0 of your library and the library version was 1.0.0.1 and you had no binding redirection configured in your .config file, a TypeLoadException will be thrown.

If the assembly in which the Type is contained is not in the current directory, a path configured in the <probing> configuration section of your .config file, or the Global Assembly Cache (GAC) a TypeLoadException will be thrown.

How can you avoid these problems? For one, stop using automatic versioning (when the AssemblyVersionAttribute contains an asterisk). This was, IMO, a bad addition to .NET because versions are VERY important in resolving assemblies, unlike native DLLs. Automatic versioning for them would've been nice (it was possible through macros) but for .NET assemblies it is bad. You have no control over the assembly versions.

Second, use project references. If you have the source to a project and want to reference the resulting assembly in another project, click on the Projects tab of the Add References dialog and add a reference to the project to be configured as a dependency. This keeps track of the outputs and will compile the same build configuration of each project (Debug, Release, etc.). This also makes sure that any changes in the dependent assembly will cause the that to be recompiled when you compile the assembly that has a that dependency. If you use a file reference, this will not happen automatically. If you continue to use automatic versioning, you should definitely use a Project reference so that any changes that cause the version # to be different will recompile the target assembly which will bind against that new version.

Finally, make sure that all dependent assemblies exist on the target machine. The base class library assemblies will already be present if .NET is installed (and obviously it must be). Make sure the correct version of .NET is installed, too. While each framework is both forward- and backward-compatible, they are not 100% compatible between versions. Things change some times so some Types may be different. Also make sure that any third-party libraries that your libraries reference are also installed into the GAC (so you don't have to worry about resolving assemblies).

Re: Could not load type.

Simon Wren12-Jan-04 2:54

Simon Wren

12-Jan-04 2:54

Great thanks, i think it must be the automatic versioning as we are using references already.

It makes sense now as the new test apps we created that did work did not have a previous reference to the component, while the app that didnt work had used a beta version of the
component.

Thanks again for your help

Simon Wren
simon.wren@nesltd.co.uk
Senior Software Architect
National Energy Services Ltd
Visit Us: www.nesltd.co.uk Or: www.nher.co.uk

Buttons?

thomasa12-Jan-04 0:41

thomasa

12-Jan-04 0:41

I have a panel consisting of buttons.

How can I select (set focus) on severel buttons?

Let's say that the panel consists of 8 buttons, first I want to groop the buttons in to two groops(4 * 2), a timer shall then switch between the two groops and by clicking the mouse, the sellected groop then gets grooped in another groop (2 * 2) and the timer switches (sets focus) between the new groop, and so on, until there is only one button left. (In Norway we call this scanning)

Is there an example of somthing like this on the web?

Since my buttons consist of pictures, I need to somehow view the buttons that are set focus on, any idees?

Thanks
Thomas
Sorry about my bad english

Re: Buttons?

Heath Stewart12-Jan-04 3:14

Heath Stewart

12-Jan-04 3:14

Focus can only be given to one active control. This is universal. By given a control focus, you give it the input focus. You can't input into two controls at once (though you can give the appearance by echoing). All modern OSes are like that.

Now, if you want the groups of buttons to be selected, that's different. Just like in Windows Explorer (or in any other window manager) you an select multiple items, but only one item has the focus. You could extend the Button class and give it a Selected property (a Boolean most likely). In the set accessor, you could flag the control and invalidate it so that next time OnPaint is called you can draw the picture differently to signify that it has been selected (perhaps drawing a rectanglular border using the Bounds rectangle).

PictureBox - Getting current mouse location

MrEyes12-Jan-04 0:13

MrEyes

12-Jan-04 0:13

Does anybody know how it would be possible to get the current mouse coordinates within a PictureBox control?

If that doesnt make sense, read on. I am playing around with creating a chess game, the board is an image that is placed within a PictureBox. To be able to process piece selections etc I need to be able to retrieve the part of the image this user has clicked on.

At the moment I am using a rather inelegant solution, by using this.location & cursor.location to calculate where the image was clicked.

post.mode = signature;
SELECT everything FROM everywhere WHERE something = something_else;
> 1 Row Returned
> 42

Re: PictureBox - Getting current mouse location

Heath Stewart12-Jan-04 3:08

Heath Stewart

12-Jan-04 3:08

In all the mouse events like MouseDown, MouseMove, and MouseUp events, the MouseEventArgs contains the X- and Y-coordinates of the client in terms of the client. How did you not notice these in your event handlers? Remember to read the documentation for important information. Since this is related to mouse events, start with the Mouse* events in your PictureBox member documentation.

You can also use the static MousePosition property (inherited from Control) to get the screen coordinates of the mouse, then translate those to client coordinates using PointToClient (inherited from Control) at any time:

Point p = Control.MousePosition;
p = myPictureBox.PointToClient(p);

On a side note, most implementations of checkered boards treat each piece as an object and the board as a grid of contains. This makes development much easier by using object-oriented development practices to control how pieces move and where and when to draw pieces. See http://www.csharphelp.com/archives/archive246.html[^] for an example.

Re: PictureBox - Getting current mouse location

MrEyes12-Jan-04 3:25

MrEyes

12-Jan-04 3:25

Thanks for the reply.

I discovered the mouse up event args on the different events a few moments before your reply came in, I like to cover all possible bases and review documentation whilst I speak to peers. I was working with mouseclick events, which does not have the necessary event args, but I shouldnt really have to justify myself. This is after all a tech community, if documentation is the golden solution you extol it to be, why doesnt CP just save the bandwidth and shutdown the tech forums. *breath*

The Game Board itself is OO based. The board object has a GetBoardImage() method which draws a image of the game board using the objects gamedata (a rather large array), this image is then passed to the picturebox.

When I first started playing with this, I did look at grids (and also creating 64 picture boxes/buttons etc OMG | :OMG:

) but for aesthetic reasons I opted for the GDI method, which works surprisingly well.

post.mode = signature;
SELECT everything FROM everywhere WHERE something = something_else;
> 1 Row Returned
> 42

Should I change C++ to C#

TWS_Dave11-Jan-04 22:27

TWS_Dave

11-Jan-04 22:27

I have read much of the Microsoft advertsing telling me how wonderfull C# is, but as a Visual C++ programmer should I make the change to C#? I have seen many articles about Java and C# but none discussing C++ and C#.

What I really need is someone experienced in C# to tell me what is wrong with it? Is it really as good as MS claim? Does it really speed up developments? What is more difficult to do using C# when compared with using C++?

Most importantly - what do you think of C#?

Dave Collins

Re: Should I change C++ to C#

Mazdak11-Jan-04 22:39

Mazdak

11-Jan-04 22:39

TWS_Dave wrote:
Does it really speed up developments?

Sure.

TWS_Dave wrote:
What is more difficult to do using C# when compared with using C++?

The more you go into system things ,the less you can do with C#,I myself think C# mostly good for bussiness and generral database developing and somethings like that,there are still some features that still only in win32 and a little hard to use in C#. I myself switch from VC++ to C# but it depends on your jobs and your requirements,for example DirectX9.0 has its own .NET version but VC still use for game developing,if I was a game developer didn't do that(at least not very soon),I myself haven't seen any game in C#,so if you say your field of work we can help you more.

TWS_Dave wrote:
Most importantly - what do you think of C#?

Its Great.

Mazy

No sig. available now.

Re: Should I change C++ to C#

Michael P Butler11-Jan-04 23:12

Michael P Butler

11-Jan-04 23:12

IMO, C# is a nice language, but it is let down by the primative set of libraries that make up the .NET framework. (primitive compared to what MFC offers) Of course, the framework is improving with each release and eventually it will be the defacto way of developing for windows.

A lot depends on how much legacy code you have in C++. If you have a great deal of time and money invested in a C++ codebase then moving may not be the best thing to do.

I have a lot of legacy apps that are C++/MFC, and I won't be migrating any of those away from C++. I have 10 years worth of development time invested in C++/MFC, so moving to C# will mean a lot of time learning the new language and how to get the best out of it.

I recommend you read the book 'Inside C#' by Tom Archer. This will give you a nice detailed look at the language, which should give you a clearer picture of where it is better than C++ and where C++ still has the advantage.

A lot depends on the kind of applications that you write. If you write a lot of database related applications, then C# is a lot quicker to use than C++. C# and ASP.NET make writing web-apps so much easier too.

Michael

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