There is a TextChanged event for the RichTextBox, what I require is a TextChanging event so I have chance to perform an action before the text is changed. The KeyDown event is not enough as my application uses a speech recognition engine which means it is possible to enter text without using the keyboard.
I was hoping I could intercept something in the WndProc method but nothing stands out.
Any ideas or help would be much appreciated. Thanks.
Try using the TextChanged Event from the RichTextBox class. Based on the description from MSDN
This event is raised if the Text property is changed by either a programmatic modification or user interaction.
It should be able to handle what you are trying to do.
Edit: You could have some sort of intermediary storage of the text so that when the text changes it is stored somewhere else first and after the text changed event is done, you can put the text back into the RichTextBox. But without knowing specifically what you are trying to accomplish, this would be my recommendation.
Related
I have a rather simple Question but I couldn't find any Answer.
My setup is the following. I have a simple WinForm application which has one Element(A) which can be dragged. He is starting a DragAndDrop event copy simple Text.
I have a second Window(B) (TextEditor e.g.) which can handle an OnDropEvent and just put in the Text.
Now my case. I want that after Drag is finished of A to B, I can handle an Event to open a new Window where you can type in more Text. This text should then be the Data which should be used by the DragAndDrop-Event.
I hope its clear and there is any good soultion.
Thanks for any help.
Best regards
I'm currently creating an application that has three textboxes. Typing into one box will result in the other two having "converted" versions of the text displayed. All three boxes can be typed into and serve the same purpose (though provide different outputs for the conversion).
The "TextChanged" event is called whenever the text value of the box is changed, that is fairly self-explanatory. But will this event also trigger if I change the value through code.
Say if I changed the first box, it would create text in the second. Would the second box trigger the event as well? And would this result in an infinite loop?
No, it wouldn't. Text taken from the MSDN page on the event:
The TextChanged event is raised when the content of the text box changes between posts to the server. The event is only raised if the text is changed by the user; the event is not raised if the text is changed programmatically.
MSDN page
Yes, or no.
this behavior differs from Winform and ASP.Net (each corresponding to System.Windows.Forms.TextBox and System.Web.UI.WebControls.TextBox), means that if you are to create ASP.Net application then the answer is no, but if you are working on Winform application then the answer is yes.
Please refer to the following different saying from the MSDN:
System.Windows.Forms.Control.TextChanged Event
Remarks
This event is raised if the Text property is changed by either a
programmatic modification or user interaction.
For more information about handling events, see Handling and Raising
Events.
System.Web.UI.WebControls.TextBox.TextChanged Event
The TextChanged event is raised when the content of the text box
changes between posts to the server. The event is only raised if the
text is changed by the user; the event is not raised if the text is
changed programmatically.
I am using WPF, MVVM-Light.
In my UI I have a textbox, and I want to prevent the user from typing certain characters in the textbox.
I know if we use code-behind I could handle the key down keyPress events, can I achieve it through MVVM?
Can we use some behaviors or some interactivity triggers?
Using code-behind is perfectly OK with MVVM providing the code-behind is related to your View only.
So if you have some view-specific logic that says "User can only type numbers in this box", then it's perfectly OK to write a KeyPress event for the TextBox that only allows numeric keys to be processed. You could even throw this into a UserControl so it can be reusable.
However if your allowed character logic is based on application logic, such as "User can only use the characters defined in the app.config file for this string value", then you'd be better off validating that in the ViewModel.
Also note that restriction is different from validation.
If you want to validate a user's entry, then I would do so using IDataErrorInfo from the ViewModel layer, and possibly a binding with a mode of UpdateSourceTrigger=PropertyChanged so the validation is checked after every key press.
If you want to restrict what characters can be typed into a TextBox, then I would probably do that from the View layer in the code behind, as that is a functionality of the View.
Yes, to filter input the MVVM way, I would suggest either using a custom control (such as a masked TextBox control) or a Behavior.
I was recently looking for a good masked TextBox and there is a free one out there from Xceed which you can find here. I can't speak to this one, as I haven't used it, but I've been happy with other Xceed components I've used in the past.
However I didn't want to go third party and include a bunch of controls I didn't need, so I ended up creating a behavior that simply attaches to the TextBox and filters the input based on a FilterType. The behavior is pretty easy to create, and you simply use the PreviewTextInput event to filter out characters that you don't want.
This SO Answer has a number of suggestions and links to how to filter/mask the input and if you're not familiar with creating Attached Behaviors, this example shows how to create an Attached Behavior for a Masked Text Box.
I am looking for something that fire before the source is update
So instead of Binding.SourceUpdated I want Binding.PreviewSourceUpdated
I think you would need to handle this on your UI element and intercept the event if it's not ideal. So for example say you had a text box and a user pressed a key. You would use the PreviewTextInput (or similar preview) to see if you wanted the data changed - then mark the event has handled if you didn't.
The only other option that I know of is to use DataValidation and not allow the property to be updated for the model side.
I have an application in which there are lot of TextBoxes and some Buttons like Save, SaveAs,etc.
When the user edits a TextBox, I have to check the DataBase for some range, validate the range and update the DataBase.
If there is any error in value entered by user,then I should not allow the TextBox to lose focus.
I was using LostFocus event for this and it was working fine until lately I discovered a bug in my application.
Bug : The user edits a value in TextBox and then clicks on Save button; the LostFocus event is not called and so Database is not getting updated :(
Now my question is which event should I use in TextBox to update the DataBase. I tried TextChanged event but it validates for every character and making my application slow. I am confused in chosing the right event for this kind of application!
Note :** The Buttons are in different UserControl !
EDIT 1 : I have some Commands attached to click of Buttons, these Commands are getting executed before LostFocus !! Can I set precedence or something like attached behaviours or commands should get executed after LostFocus !!
EDIT 2 : I was just debugging the application by disabling some commands, what I found was in some cases, the DelegateCommand gets executed before LostFocus, so I want to avoid that. How can I go about it ? I felt during development its impossible to developa pure MVVM application so I am kind of using a bit of codebehind !
Trapping the keyboard focus within a control is usually a sign of bad UI design - it's pretty user-hostile to force the user to fix data in a control before he can type anywhere else in the UI.
That said, you shouldn't be using events at all here. You're trying to write a Windows Forms application in WPF. You should write a WPF application.
Create a class that is a logical model of your view - i.e., there's a string property for the text box and a Command property (or, more likely, a RelayCommand) for the Save button. Bind the text box to the string property, e.g.:
<TextBox Text="{Binding MyTextProperty, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
Because the UpdateSourceTrigger is PropertyChanged, the source object will get updated every time the user types a character.
Bind the button to the command property, e.g.:
<Button CommandBinding="{Binding SaveCommand}">Save</Button>
Implement the appropriate CanSave and Save methods that the RelayCommand (as described in Josh Smith's essential article on the MVVM pattern) requires, so that the button is enabled when the string property is valid and disabled when it's not.
I think the best approach is preventing a user to proceed until all valid information has been gathered.
Just like an installation wizard with Terms & Conditions Dialog and Next button. Until you check the I Agree checkbox, Next button is disabled.
This way, you don't have to worry about user proceeding without providing valid information. This way, you can use any event on TextBox to validate your data.