I want to check what the user is writing in a textbox before I save it in a database. What is the best way to do this? I guess I can always write some ifs or some try-catch blocks, but I was wondering if there's a better method. I've read something about Validating Events, but I am not sure how can I use them.
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Can I make a recommendation that you start migrating from WinForms to a more modern platformScottishTapWater– ScottishTapWater2020-11-06 14:20:39 +00:00Commented Nov 6, 2020 at 14:20
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2 Answers
Description
There are many ways to validate your TextBox. You can do this on every keystroke, at a later time, or on the Validating event.
The Validating event gets fired if your TextBox looses focus. When the user clicks on a other Control, for example. If your set e.Cancel = true the TextBox doesn't lose the focus.
MSDN - Control.Validating Event When you change the focus by using the keyboard (TAB, SHIFT+TAB, and so on), by calling the Select or SelectNextControl methods, or by setting the ContainerControl.ActiveControl property to the current form, focus events occur in the following order
Enter
GotFocus
Leave
Validating
Validated
LostFocus
When you change the focus by using the mouse or by calling the Focus method, focus events occur in the following order:
Enter
GotFocus
LostFocus
Leave
Validating
Validated
Sample Validating Event
private void textBox1_Validating(object sender, CancelEventArgs e)
{
if (textBox1.Text != "something")
e.Cancel = true;
}
Update
You can use the ErrorProvider to visualize that your TextBox is not valid.
Check out Using Error Provider Control in Windows Forms and C#
More Information
Comments
With WinForms you can use the ErrorProvider in conjunction with the Validating event to handle the validation of user input. The Validating event provides the hook to perform the validation and ErrorProvider gives a nice consistent approach to providing the user with feedback on any error conditions.
http://msdn.microsoft.com/en-us/library/system.windows.forms.errorprovider.aspx
1 Comment
MKesper
Beware though: The ErrorProvider component does not provide built-in support for accessibility clients. To make your application accessible when using this component, you must provide an additional, accessible feedback mechanism. (msdn.microsoft.com/en-us/library/…)