Set Focus Problem With Usercontrol(DGV) And Other Controls(textBox)

Question

I have a user control Datagridview which is derived from windows.forms.datagridview class and Textbox control in my forms and I have set the tabindex of control as below

Datagridview------ tabindex = 0

Textbox------------ tabindex =1

I have set mydatagridview as enter key like tab behavior and it's works fine but problem is that how to set focus on textbox control which is on main form by enterkey.

The code of Setting DGV by Enter keys as below:

public class mydatagridview : DataGridView

{

protected override bool ProcessDataGridViewKey(KeyEventArgs e)

{

if (e.KeyCode == Keys.Enter)

{

this.ProcessTabKey(e.KeyData);

return true;

}

return base.ProcessDataGridViewKey(e);

}

protected override bool ProcessDialogKey(Keys keyData)

{

if (keyData == Keys.Enter)

{

this.ProcessTabKey(keyData);

return true;

SendKeys.Send("{tab}");

}

return base.ProcessDialogKey(keyData);

}

How to Set Focus on Textbox by Enterkey on my main forms?.

Sam Hobbs · Answer

I think the attached shows how to do what you are requesting. The code is a bit more complicated because it tries to show going both directions; when you execute the sample try using shift-enter to go backwards. You will see that all the code for processing the enter key is in the MyDataGridView class. However in my sample I don't have a control preceding the MyDataGridView so you won't see that working unless you add a third control and set the tab order such that there is a control preceding the MyDataGridView and following it in the tab order. Don't ask me why there is both a ProcessDialogKey method and a ProcessDataGridViewKey method; I don't know why but it seems to be necessary.

Sam Hobbs · Answer

To continue with the discussion of subclassing and classes and such Microsoft uses confusing terminology. When we use the IDE (VS) to create a custom control the control has code to do owner-drawn painting. So Microsoft uses the term custom control for owner-drawn controls. Also in the IDE the template for creating an Inherited User Control is for creating a control that inherits from another control. The terminology is inconsistent and confusing. So I certainly misunderstood the original question because it says  user control Datagridview . I don't know for sure but that might be what some people in Microsoft call a control that is inherited from a DataGridView  but that sure confused me. Yes Windows programmers used the terms subclass and window class before C++ classes were designed; many years before .Net existed.

Vulpes · Answer

I don't really agree with Sam on the semantics of this one. In object oriented programming a subclass is a class which derives from another class and subclassing is the process of creating such a subclass. Now when you're subclassing a Windows Form's control you will inherit the protected virtual method WndProc() from the Control class and can choose to override it or to use the base class implementation. This method corresponds to the unmanaged WindowProc callback function which processes messages sent to a window and so if you do override it you'd generally handle one or more messages yourself but pass the remainder through to the base class for processing in the normal way. So I would maintain that creating a custom control always involves subclassing a base class control and may or may not involve overriding WndProc.

Vulpes · Answer

The only way I can think of doing it is to check whether the current cell is the last one in the DGV when enter is pressed and if it is move to the next control. You'll need to set the Form's KeyPreview property to true and then handle the Form's KeyDown event as follows: private void Form1_KeyDown(object sender KeyEventArgs e) { if (e.KeyCode == Keys.Enter && ActiveControl == mydatagridview1) { Point p = mydatagridview1.CurrentCellAddress; if (p.Y == mydatagridview1.Rows.Count - 1 && p.X == mydatagridview1.Columns.Count - 1) { this.SelectNextControl(ActiveControl true true true true); e.Handled = true; } } }

mahesh waghela · Answer

Yes I agree with Vulpes as it will helpful for others. Especially MyDatagridview Class:

Sam Hobbs · Answer

In the past I included code more often; here in these forums and before that in the MSDN forums and before that in the CodeGuru forums. I currently hope to spend time writing some articles. The code I posted here took time to figure out. What I should do is to spend time learning more about how that works and then make it an article.

Vulpes · Answer

Yes a good effort Sam and nice tidy code too. You should include code with your posts more often :)

mahesh waghela · Answer

Hi Sam It's a good solution which is attached here. I am appreciate your efforts and thanks for the same.And by the way there is no need of third control to add. It will run by add it directly to the main controls/parent control and it will executed. Now I want to discuss about your line of second post on 09 may 2011  in the IDE the template for creating an Inherited User Controls is for creating a control that inherits from another control.. Generally Controls are inherited from common base class or Microsoft Control.And User Controls are always derived from the Common base Class Or Microsoft Windows Controls and hence User Controls cannot inherited like Microsoft controls as it's derived from the Microsoft Controls.

Sam Hobbs · Answer

Any questions about my sample?

Vulpes · Answer

Well it's an old article (January 2002) Mahesh and I'm surprised it hasn't been removed by now! This is because it's actually wrong when it says that: .NET controls are all inherited from a common base class called UserControl. The common base class is in fact simply called Control and you can see this by looking at the inheritance tree of a control such as TextBox ( http://msdn.microsoft.com/en-us/library/system.windows.forms.textbox.aspx ). The UserControl class ( http://msdn.microsoft.com/en-us/library/system.windows.forms.usercontrol.aspx ) also derives ultimately from Control though it's direct base class is ContainerControl. As far as I can recall this has been the position since .NET was first publicly released though it might have been different in the beta version on which that article was probably based. Just coming back briefly on the articles Sam has found. Although unmanaged Win32 programming has the concept of a 'window class' it's not a class in the object oriented sense which supports inheritance virtual methods etc. It's just a set of attributes together with a pointer to its window procedure. Consequently when you 'subclass' a control you replace its window procedure with a new one. So I think the difference between Sam and me on this is that he's been thinking about subclassing in the above sense and I've been thinking about it in an inheritance sense which is born out by the articles. However I'm coming around to the view that it's better not to call it 'subclassing' when creating a .NET custom control but to call it 'deriving' instead to avoid any confusion with subclassing in the unmanaged sense. This in fact is what an old book I have on .NET Windows Forms programming calls it :)

mahesh waghela · Answer

Vulpes and Sam Hobbs You guys are rocking. I am really having interest in both of you. The above topics are very well discussed here and I love to gain knowledge by discussing and hence I like to draw your attention towards the link about user control: http://msdn.microsoft.com/en-us/library/aa302342.aspx In which they have clearly stated that : when controls are inherited from common base class of windows form controls are called UserControls and also I would like to draw your attention towards Overview Of User Controls and Creating of your own controls vs Microsoft Controls. In which the author have clear the use and definition of user controls.

Sam Hobbs · Answer

The article Subclassing Controls with a Managed Window Procedure describes subclassing native windows by managed programs and Subclassing Controls and Using Window Procedures describes subclassing for unmanaged programs. They describe subclassing in the manner I described. The KB article How to subclass Windows in Windows Forms by using Visual C# .NET or Visual C# 2005 describes subclassing the way Vulpes describes using inheritance. As for the original question today was a busy day for me. I spent more time on the application idle question than I have on any question lately. I will look at this some more when I can.

Sam Hobbs · Answer

Subclassing is replacing the window's procedure with our own and the new procedure calls the other procedure to have done whatever that procedure does. Subclassing gives the new procedure the opportunity to do something different. For .Net controls the subclassing is done in the .Net control class. When we derive a class from them we are overriding the class but we are using the same Windows procedure. So I think it would not be called subclassing. MFC for example did subclass controls to allow derived classes to be used and then there was a problem that the derived classes would not process Windows messages sent prior to the subclassing. The .Net classes don't have that problem.

Vulpes · Answer

Technically what you're doing here is called 'sub-classing' a control and the resulting class is often called a 'custom control'. In contrast a UserControl is a container for other controls - a sort of 'mini' form.

mahesh waghela · Answer

Sam Hobbs Ok than if somebody inheritance the controls from windows.system.Control Name than what you call it?.

Sam Hobbs · Answer

You say  datagridview user control  but a DataGridView is not a UserControl. I get the impression that you do not need to use a DataGridView in a UserControl so I will make a sample that does not use a UserControl.

mahesh waghela · Answer

Sam Hobbs I am also interested in other option for solution.and about your question i like to reply that Vulpes answer is perfect solution of my question and you can try it by various way of R&D. If you have other option than suggest us it would lot help to me as well as to our community. Now i am utilize the user control of DGV for only purpose of Enter Key where as Windows.System.datagridview has only tab key process that's why I am planning to utilize datagridview user control.

Sam Hobbs · Answer

I would sure try to make a more object-oriented solution; I will be surprised if there is not one. If however you are not inerested in other possibilities I will not spend more time on this. If you are interested in another possibility then please explain why the DataGridView is in a UserControl. There could be a very good reason but to the extent that it could affect the alternative solution I am interested in knowing why. I am not sure if ProcessTabKey will allow the focus to leave the UserControl; if not then perhaps it is simply a matter of changing that behavior. Or perhaps the solution is to simply not use a UserControl.

mahesh waghela · Answer

hi vulpes Nice way I like it.