How to focus on a textbox from a Form shown as a dialog?

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I have a textbox, when a user input invalid data and leave the textbox, a form will be displayed by the ShowDialog method to inform that the data is invalid and ask if the user wants to re-enter. If he/she wants that, it should set FOCUS on the textbox. But it is not simple. Here is my code:

C#

private void OnLostFocus(object sender, EventArgs e)
{
   if(ReEnter) 
   {
     ReEnter = false;
     return;
   }
   if(!IsValidData()) 
   {
    MsgBox M = new MsgBox();
    M.ShowDialog();
    if(M.DialogResult = DialogResult.OK)
      {
        ReEnter = true;
        textBox1.Focus();
      }
   }
}

IsValidData() is my method to check if the data is valid, my ReEnter is to mark that the user wants to re-enter.
I think it should work, but it works a very strange way, even the ReEnter never comes true (when OK accepted to re-enter), that makes a loop of hiding and showing the dialog. I can't make it work as I want. Could you please see and check and test your own code to help me out of this problem. I want the data validity check will be fulfiled whenever the user leaves the textbox!
Thank you so much!

Posted 17-Apr-11 8:32am

King Boy

Updated 17-Apr-11 8:35am

Albin Abel

v2

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Fabio V Silva · Accepted Answer · 2011-04-17T08:36:00

Solution 1

Call the textBox1.Focus() method on the IsValidData() method if the data is not valid instead of using the ReEnter variable and events.

Posted 17-Apr-11 8:36am

Fabio V Silva

Comments

Sergey Alexandrovich Kryukov 17-Apr-11 14:39pm

Simple as that, my 5.
--SA

Fabio V Silva 17-Apr-11 14:40pm

Thanks :)

Albin Abel 17-Apr-11 14:48pm

But I guess IsValidData() is a business logic, hopefully return a bool. Do you suggest mix it up with UI?. Actually the error is here if(M.DialogResult = DialogResult.OK) :)

[no name] 17-Apr-11 15:02pm

Did you mean all the code in OnLostFocus should be placed in IsValidData()?
But I want IsValidData() to be called when the textbox loses focus, so I have to use event here! Is there another way? Haha! I have found the reason! A difference between OnLostFocus and OnLeave. Yeah, I replaced OnLostFocus by OnLeave, it works well without any loop of hiding and showing. I think that's it, could you please explain more? Thank you!

Fabio V Silva 17-Apr-11 15:06pm

private void OnLeave(object sender, EventArgs e)
{
if(!IsValidData())
{
MsgBox M = new MsgBox();
M.ShowDialog();
if(M.DialogResult = DialogResult.OK)
{
textBox1.Focus();
}
}
}

No need to use the ReEnter variable.

[no name] 17-Apr-11 15:04pm

Oh, no, that error of mistyping is not problem, if it is that, why could it run with a loop of hiding and showing? Thanks!

Albin Abel · Accepted Answer · 2011-04-17T08:45:00

Solution 2

Hi should be if(M.DialogResult == DialogResult.OK). Single = is an assignment operator, not compare operator. If it is a simple message box you can use inbuilt System.Windows.Forms.MessageBox. No need a separate form.

Good luck

Posted 17-Apr-11 8:45am

Albin Abel

Comments

[no name] 17-Apr-11 15:01pm

Ah, I mistyped it! Thank you! But Does message box support Vietnamese? Yeah, that's why I use a form as a dialog instead! Thank you again!

[no name] 17-Apr-11 15:12pm

I mean we only have "Yes" , "No" ... buttons but not have "Có" , "Không" (in Vietnamese). Of course the message can be written in Vietnamese. I love .NET, as before when programming with Visual basic 6.0, writing a message in Vietnamese is a very hard work!
Thank you!

Albin Abel 17-Apr-11 16:30pm

Right. For that reason as Fabio V Silva said use the leave event handler not the lost focus..
private void Form1_Load(object sender, EventArgs e)
{
textBox1.Leave+=new EventHandler(textBox1_Leave);
}
private void textBox1_Leave(object sender, EventArgs e)
{
Form2 testDialog = new Form2();
if (testDialog.ShowDialog(this) == DialogResult.OK)
{
this.Focus();
}
}
Don't forgot to return correct dialog result from the dialog form. good luck

Sandeep Mewara 27-Apr-11 12:10pm

Right! Good followup too. 5!