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Gideon - when I wanted automatic control of UI elements, I knocked up this[^] sample. It's a trivial example, but easily extendable into something more powerful (we did).
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Hello,
I am not sure if it is a good suggestion or not as I have done it myself but you can use Command pattern for your application. You can use databinding to bind several ui controls to one ICommand object and then changing enabled/visible property of the ICommand will automatically enable/disable, hide/show by the magic of databinding 
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hi,
Thanks you guys, but un fortunately UI needs to be disabled based on more complicated situations. Like User permissions, and things like say if its a customer's last day of stay, stuff like that.
I will have a customer grid, so if a certain customer is on his last day, in the user control I would do this:
if(selectedReservation.EndDate == DateTime.Today)<br />
{<br />
} else {<br />
}<br />
I can't put all possibilities into an Enum, and I think databinding would be a little convoluted since some situations are more complex.
Is my design stupid? that I'm looping through the controls?
Thanks so much.
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giddy_guitarist wrote: Is my design stupid? that I'm looping through the controls?
I don't think there is much else to do really. It just ties your code really tight to your business rules in the UI.
You may want to take a hybrid look and do both. Look at what can be done via a form based state machine then augment that with some business rule specific stuff.
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Hi
As Giorgi mentioned, the command pattern allows you the control of enabling/disabling.
You will find an example for WPF here WPF Command-Pattern Applied[^]
Here you will find an example for WinForms[^].
Regards,
Jani
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I would split the UI management into 2 distinct types, 1 based on permissions and user group membership and 2 state of the data. Either way it is custom coding for each form.
I like the idea of binding the enabled/visible attribute.
I use a permissions table that is returned from the login with all the permissions for the logged in user. Then each form checks this table for defined controls. While I implement this in all apps it is rarely used(corporate).
Never underestimate the power of human stupidity
RAH
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I think using the MVC pattern is a good solution. I use it all the time. With events the whole process becomes easy.
Create an event in your business object called Validated or something, have the User Interface subscribe to this event. Within the handler put the logic for enabling/disabling control.
Find out ALL the condition which will enable and disable your control and use boolean logic like below:
nameOfButton.Enabled = customer.IsActive && customer.IsValid && someotherCondition || someotherCondition && (someotherCondition || !somotherCondition)
I like this solution because all the rules for the ability of my control are in one spot and the button will only be enabled if all conditions are satisfied.
One thing you want to stay away from is code such as nameOfButton.Enabled = true. Reason being is that somewhere another programmer, or yourself will have another similar call that disables the button. The latest call will actually decide the ability of the button. In situations like this you end up with a lot of if statements and things become very ugly soon.
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Interesting,
I've been quiet for sometime because I was doing a little more thinking, I decided to use the MVP pattern for each UserControl(View) that I make, however what I was talking about was Enabling/Disabling a control in the MainForm from a UserControl, I would end up having a reference to the MainForm from the UserControl then, which glues the UserControl to the MainForm!
MainForm
---------------------
CustomerView(UserControl): A customer is selected, something needs to be disabled in the MainForm.
BillView(UserControl)
---------------------
But now,
It seems I will only have a MenuBar and a ToolBar on the MainForm, there will also be a TabControl and inside these TabControls will reside different views. So I just have to bother about diabling/enabling menus and toolstripitems.
Now, I thought of encapsulating the Toolbar and MenuBar and have themselves decide what needs to be enabled and disabled instead.
Like
class HmsMenuBar : MenuStrip
{
//during the OnDropDownOpening.. i can check if items should be enabled/disabled.??
}
Same thing for the ToolBar, does this sound ok?
Thanks so much
Gideon
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UI controls, whether the main form or the User Control is just a mechanism to allow a user to interact with the underlying. What I do not understand is why you want the user control to enable/disable main forms controls: They must know about each others controls and adds to coupling which is not ideal. If you want a menu item to enable/disable based on customer's last day or whatever, then have both the main form and the user control subscribe to the customer. UserControl will do what it is supposed to do and main form will do what it is supposed to do. Now these UI elements only know about the "thing", in this case the Customer, they are displaying but not about each other.
It will be like this: Customer is loaded and obviously properties will change, then the UI Control will subscribe to an event from customer--you have to create the events based on your requirements. In this handler, the control will ask the customer for whatever it is interested in, for example, IsLastDayOfStay, if true will enable itself and false otherwise. The main form will also subscribe, and ask for something else and mold itself accordingly. You can also design it so the form does not need to ask the Customer, but the event arguments can have the information in it. For this, you would need to create a simple class to encapsulate even arguments.
The only problem is the controls are tied to your object.
If I am not understanding what you want to do, then just write in plain English with no code what it is you want to achieve and hopefully I or someone else can give you a suggestion.
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I kinda understood what your saying better after looking at paint.net source code lol! I've been looking at a lot of programs like that for inspiration.
So the Main form code itself should decide what menus and toolbars need to be enabled/disabled by querying/using business objects itself? That would be a correct design? (Atleast thats how it is in Paint.NET)
(I'm sorry if i sound daft from time to time, I'm young and not formally computer educated!)
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I'm looking for a tool where I maintain a simple data model, and then using possibly plug-ins, generate actual databases for MSSQL and mySQL, and as a bonus, others. This should not be a whole ORM tool, just abstract to concrete data model. Where should I look? Who knows of one?
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Hi Brad
Please don't pre-judge ORM solutions. With good engineering concepts and common sense you can take a good approach with this point of view
I invite you to visite our solution at www.codeplex.com/circo (not a ORM from books but form the experience of engineers who needs to struggle with diferent customers, clients, languages an programming cultures)
I hope you find useful this ideas and esentially the implementation
Regards
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Very often it is advantageous to invoke certain validation logic on client and server, especially if they are not always connected, or if another, uncontrolled client uses the server. I mean less of the simple validations, such as 'Surname must be present', although I don't exclude that, but rules such as a document billed date should generate a warning if more than thirty days before or after the current day.
A ideal solution would be one server validation engine that receives client requests to check single rules, or even a collection of rules, before the more expensive submission of the whole document. Some constraints, such as minimising server requests, or allowing the client to perform a validation and local saving of a document while disconnected, exclude this solution.
A possible solution after that is to use the same validation library on client and server, which has the advantage that additional, external clients could also make use of that library. One happy family, all using the same properly designed, implemented, and tested library.
The biggest, and in my opinion, most common problem with this is with web applications. Validation code on web pages is normally done in JavaScript, or a higher order JavaScript library, where the server validation code is written in C#, VB.NET, Java, etc. This means the validation code cannot be shared, but must be separately implemented in another language, probably by another coder. Both this language and this coder handle things differently to the combination that developed the server side validation library or routines. This means maintenance to validation code must be done in two places, and in two languages, on two platforms, and for me, only two variants of this code is slightly optimistic in some cases.
Last modified: 12mins after originally posted --
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Hi,
I'm learning how Silverlight/WPFapplication/Direct3D interact between themselves...
Sorry but I haven't a lot experience about this issues, so my question is:
- IS IT POSSIBLE, WITH SILVERLIGHT, TO RENDER WPF FILES IN A DIREC3D/WIN32 APPLICATION? HOW CAN DO IT?
Thanks a lots,
bye,
Carmelo.
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You are Posting in a Wrong Place , go to Silverlight Forum, i think i saw your Qustion somewhere ,Stop Cross Posting
Vuyiswa Maseko,
Sorrow is Better than Laughter, it may Sadden your Face, but It sharpens your Understanding
VB.NET/SQL7/2000/2005
http://vuyiswamb.007ihost.com
http://Ecadre.007ihost.com
vuyiswam@tshwane.gov.za
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What is the best way to structure class objects in a program that allows me to search for values from different properties of the class?
I am making an application that holds client name, address phone and note information. I created a Client class that holds all these together. In my main program, I was putting each new client in an array list, but I ran across a problem. I can't search my array list for just a first or last name.
I don't think that overriding the Equals function of my class would allow me to change that, so I started looking at other ways to hold my data.
If I created another value in my class, like an ID field, I could create a hash table that was a ID/value pair (ID/First Name, ID/Last Name, ID/Address, ect). This would allow me to search each hash table and find the ID to get the full record, but that would mean I would need a table for each field that I would want to search. At this point, I'm a bit stuck on the best way to set my data structure up.
If there's some articles that give some guidance and suggestions, I would appreciate it. I can't seem to find anything because I don't think I'm using the right terminology.
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hpjchobbes wrote: but that would mean I would need a table for each field that I would want to search
Consider this the way that DBs do it. That is (at a high level) what gets created when you form an index on a table. That's why you really should not go and create indexes on every attribute of an entity.
One thing you could consider doing is instead of storing the data in an array list of objects in memory, store it in an in memory data-set. That way you can query it using standard SQL queries all you want. Wrap the collection in a class that uses an data set internally to store the data and returns collections of objects to you as the result. That way you can keep your data in a simple search-able format and still get objects to work with latter.
I am sure that someone here could also come up with some cool alternatives using objects and LINQ, but I am not all up on that tech yet
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I'm just starting to learn programming, so I was trying to keep my implementation simple, but I guess this is a bit more complex problem that I originally thought! I guess for my simple application having a hash table for each field is probably the easiest way to go.
I didn't even think of making my own collection class, but that seems like it might be a good way to go to learn more about databases before I start diving into some of the main databases out there. I'm not to the point where I need to worry about handling large amounts of data, so for now, I'll keep it simple.
Thanks for the information!
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keeping it simple is always good, just build it so that you can extend it latter without having to redo too much of the host application. Always be thinking about encapsulation, even when trying to keep it simpler.
Things have a way of getting away from you and not staying simple for long
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Overriding Equals is only for comparing if objects are the same.
Ignoring indexes, if you need to search a List< Person> then you can do it by hand. Iterate over the list with foreach, and put the results into your result list when the fields match. If you are using a later version of the framework you can pass an anonymous method into the .Find(Predicate< T>) method. This would look like this:
List< Person> results = data.Find(delegate (Person p) { return p.Name == searchName; });
Or in a lambda expression:
List< Person> results = data.Find(p => p.Name == searchName);
If you are just starting programming then worry about the basics first. As for indexing, you should either use a database (Diamond Binding in my sig will make it pretty easy for you) or if you want a pure object solution then you might want to check out a pure object database. db4objects is a very good object database, but can be quite expensive. Generally in the "real world" you would rarely be writing your index code by hand (but it is important to be aware of lookup performance in your data structures).
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Thanks for the response! The .Find(Predicate<t>) function is interesting and I'm going to be looking into that more. All my programming is really for learning purposes, so I tend to try and stay away from solutions that have been built for me as I don't feel that I get a good understanding of what is going on. It's probably not the 'best' method for learning, but it seems to work decent for me.
What I just thought about now, seeing you mention using List<t> instead of ArrayList is how the two differ. I would imagine that ArrayList just boxes everything into an object, where List uses the base type. Would this make it faster to search through a List than an ArrayList as there is no need for un-boxing? I guess there's another topic added to my list of things to research!
Thanks for the information!
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Yeah theres a bit of history there. List< T> is a generic list, which means when you use say List< Foo> you have effectively created a brand new type out of thin air, a List of Foos. Before framework 2, generics didn't exist in the runtime, and ArrayList was a provided and the commonly used IList implementation.
Both are implemented the same under the hood, they both wrap an array which they resize as necessary. For new development you may as well use List< object> over ArrayList, they are functionally identical, but using List< object> makes it very clear that you know the generic class exists - and thus the list is actually full of random crap.
I guess the generic list would remove any unboxing that happens, I had never really looked at it that way (it would definitely help with the semantics of having to do foo = (long)(int)objectWhichIsReallyABoxedInt).
As you learn programming you will hear a lot of people talking (mostly crap) about optimisation. Generally speaking you should look out for the big-O order of things, and obvious problems like doing a bunch of high-latency things in serial. Most things like "avoiding boxing", "avoiding reflection" make little difference to a real world application. In fact I've seen a great many "tips for faster code" that results in identical IL (and thats before JIT optimisation). I use reflection extensively in Entanglar (even in the renderer I'm working on), and the performance of that is more than acceptable.
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What if you did something like this:
Create a class called ClientCollection which will have all the clients in some data structure of your choice. Within this class (ClientCollection) have a method called Search, or Find which will take 2 parameters: 1. The property to search by and 2. The value to search for. Within this method create a Dictionary and put all your clients into it. The property to search by will be the Key, and the value will be the Clients. Afterwards, call the Contains method of the Dictionary to search the value passed in.
Of course, this means that if you have many clients putting them into the Dictionary will take time.
I will also do what you suggested above in addition to this but create tables for the field(s) which will be used mostly for searching.
Now you don't have too many tables, but you are also providing the flexibility of searching by any field.
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