I see a 'Tag' property in the design view for most WinForms controls. I have never used this tag and want to know why I would want to use it.
It allows you to store some of your own data with a control. It mostly useful in tree controls where you might want each node/leaf to have some extra data associated with it. This way when you click on a node you can perform an action relevant to the node.
Its a general "catch-all" for additional data you wish to store with a control.
I too have never used it.
We perform heavy use of tags. We have some methods for checking input, and these methods checks whats in the tags in order to know what control to perform.
IE: if a textbox has RQ=1;DT=int;MAX=100
the automatic method knows that this text can not be left blank, that should accept only integers within 0 and 100.
We have a complete pseudo declarative language for this.
Kind of useful!
More specific for your question, Tags are for your use.
for example you have a lot of buttons with single method handling clicks. then at handler you have do differentiate them from each other. So you put some sort of id (or reference) and then access it there.
Related
How could I interpolate a one-time binding manually?
Here is my use case.
I have a list of a lot of elements. The elements just sets of controls. I get the data for the elements from the BE. Then I would like to leverage the AngularJS interpolation and set the controls` values. But I would like to avoid the interpolation of all the elements every time I change only a single control.
So, I use a one-time binding to set the values, but then when I change them they are not updated.
The expected result in the example is that once something is typed in the control, the respective one-time binded value is updated. Also, the one-time binding should remain there, since in my real case there will be a lot of controls and I do not want to strain performance when only one control is interacted with. A simplified example of mine can be found here (in my real case I have not only inputs, but checkboxes as well, but I believe that the approach should be the same for them).
After a research I found out that a directive should be used in this case. But I was not able to find a simple to understand example. So, could someone post it here, please?
Different from a directive solutions are welcome here as well.
First to understand your problem: Why do you want to avoid the angular change detection here? The only reason that comes to my mind would be heavy performance problems.
In one case here, there were one or two thousand of inputs, all with a binding. The application was a little sluggish, but still usable. We accepted this, as we had to re-implement all the binding manually otherwise.
If your binding is rather simple (no validations, conversions, etc.) and the values are not shown on other places while being edited, maybe it would be a way for you to use an AngularJS directive on a native HTML Input element that just listens to its onChange event to save changed data and gets updated programmatically whenever you know it changed from outside (if it does at all).
(Not talking about better using Angular, which has a much tighter grip on change detection ;-) ).
I've thoroughly checked the custom controls topic, spent several hours looking into custom controls written by other people. I've written my own custom button, to feel it better. I've read all the google answers around the "why custom controls", "advanced custom controls examples" and such.
My question is, WHY?
Why would I (or anybody) go through 9 circles of hell to create his own custom control, when one can just adjust an existing control to his needs (using styles and templates). I actually didn't find any explanation on google, just tons of examples, mostly from people who sound even less educated than me.
I imagine there IS such need, when talking about some complicated DataGrid with, I don't know, every cell being a button or something (and still I believe I could do it with a regular DataGrid)... But I've not found anything more complex than a beautiful button. Is there nobody sharing a complicated code on the topic?
There are different levels of element customization in WPF, depending what class you extend from. Each has its own uses and is implemented differently. It is not clear from your question if you are asking about a specific type of control or about all of them in general. So, I will tell you what I think about different ones.
UIElement or FrameworkElement
Extending UIElement gives you the lowest level custom control where you have complete control over the layout and rendering. FrameworkElement is slightly higher level as it does most of the common layout stuff for you while also allowing you to override key parts of it. The main idea with these is that they do their own rendering rather than composing other elements together.
I have made a number of custom FrameworkElements over the years. One example is a ruler similar to one you might find in a program like Photoshop. It has a bunch of properties providing customization for how it is displayed as well as showing markers indicating mouse position relative to the ruler (and a number of other little optional features). I have used it in two different professional projects. I think the main benefit is that it is extremely easy to drop in and set properties/bindings on wherever desired. Build it once, use it over and over.
Control
Extending Control introduces the concept of compositing multiple elements/controls into one reusable component via control templates.
I have used this one less often, but still find it very valuable in the right circumstances. Again, the main benefit here is reusability. You create a control with properties that make sense for what you want to do, then hook up those properties to the properties of the controls in it's control template. Really, this is the same as applying a new template to an existing control, with the added feature of being able to define your own dependency properties. You also have the ability to perform custom logic in the control's code if you need to.
I may be misreading some of your text, but you seem to imply that making a custom control is considerably more difficult than making a control template for an existing control. I have found that the two are nearly identical in most cases using this approach, the only difference being whether you have a code behind you can use.
User Control
A user control is really only slightly different from a custom control practically speaking. Only, instead of defining a control template, you define the visual content directly.
This is probably the most common type of custom control. It is basically the standard method for making XAML based content in a WPF application. These can be reused like other controls, but are more suited for single use such as the content of a dialog or window or something else that is specific to a single application.
Some Other Control
You can also extend an existing control to add additional functionality to it. This way, you still get all the features the control offers and only have to implement the additional bit.
For example, I have a custom control called an AutoScrollRichTextBox that extends RichTextBox. So, it does everything a RichTextBox can do. It also has the ability to automatically scroll to the bottom when content is added to the text box (which it only does if the text box was already scrolled to the bottom before the addition content was added).
I could have implemented that feature as an attached property instead of an extension of the control (and maybe I should have), but it works, and I have used it in three different applications (as an output window and as a chat log). So, I am happy with it.
In the end, it really is just a matter of how self-contained, reusable, and easy to drop in you want a control to be. If there is already a control that does what you want, and you just want it to look different, then you should definitely use styles and templates to achieve that. However, if you want to make something that doesn't already exist, limiting yourself to using only styles and templates will make the implementation work harder and make the end result less reusable and more difficult to set up additional instances (unless all instances are identical).
The examples of making things like buttons that look different are not examples of what you should use a custom control for. They are just examples of how someone would go about making a custom control for the purpose of teaching the details of the process. If you actually want a customized button, just customize a button.
I'm currently spiking with the WPF RichTextBox before I decide whether or not it can be used in a project of mine.
What I need is to have elements of text representing various objects (other texts or objects), a bit like a WIKI but not quite. Clicking on such a text will make stuff happen, like navigating to other texts or providing additional options.
Anyway, as these little text bits represent other objects I would like to protect them but I have succeeded with this only in part: The user cannot position a caret inside such a text element and edit/delete it but it is still possible to make a selection and delete/replace it, including my custom elements.
Have anyone travelled down this road with the RichTextBox? My latest experiment was to simply record all custom text elements when being part of a selection and then restoring them after the (destructive) edit. That fell apart because I can't find a way to re-insert my custom inline elements (derived from the Run class). The only way I've found to programmatically insert a Run (based) element at a specified position (TextPosition) is via its constructor.
Well, any hints would be greatly appreciated.
You are really looking for a FlowDocument, not a RichTextBox.
Basically I use lists to display information, these lists contain custom data items I have created, they all look similar and have some of the same controls in them, essentially they need to look the same colour, font etc. At the moment, I just seem to be repeating code over and over each time a change is needed i.e. colour.
I have been wondering if it would be a good idea to create a generic data item which all the lists use and then just collapse controls which aren't needed.
So I was going to create a user control called something like "GenericDataItem". This data item will contain all the controls that each data item would need, then use dependency properties to collapse controls not required.
My question is would this be the right way to go about this, or is there a better way?
Thanks.
Not sure I got the point, but using DataTemplateSelector could help you.
I have a Button in Silverlight. I need to change its style at runtime. The style of this Button needs to change multiple times during the life of the application. Is this possible in Silverlight? If not, what is a good workaround?
Thank you!
Consider using the VisualStateManager to change the state of the button as appropriate.
You could create your own states for each of the different styles you wish to show.
Yes, it's possible, but I'd think hard about what exactly you're trying to do by changing the style itself because there's probably an easier way. You've probably already run into the fact that you can't simply assign a new style to the button with something like MyButton.Style = (Style)FindName("NewButtonStyle"). So you do need some kind of alternative.
The VisualStateManager is the first and easiest way of handling most kinds of changes that you would normally want to do to a control. You can pretty easily set changes to occur on the normal sorts of visible states (hover, focus, mousedown, mouseup) and it'll animate those state changes correctly from whatever state you're in to whatever other state you need.
If the kind of change you're looking for is more extensive, changing the type of control to, say, a ContentControl and then catching the mousedown/mouseup events from there might be a better workaround. This is obviously a bigger deal (and you lose the simplicity of having a button), but you'd be able to get whatever changes you wanted to pretty easily by just swapping out the Content property.
Somewhere between the two (and something I'll mention because it's possible, not because I recommend it) would be to actually manipulate the Style definition itself. The Button will pick up the changes and adjust itself. I'm going to repeat myself here though: I don't recommend this and I can't envision a scenario where I'd prefer doing this over using the VSM or using something other than a Button entirely. But it is possible to get into Application.Current.Resources["Style"] as Style and muck about with whatever you please. The bigger question then is why and whether what you're doing can be done some other way that would make more sense for whoever's going to maintain your code later. Personally, I expect Styles to be pretty static and I think that's the general consensus too.
Sure you can....
if you have a style stored locally you can access it like that :
rec1.Style = (Style)this.Resources["style1"];