- #Vb net textbox validating event errorprovider software#
- #Vb net textbox validating event errorprovider code#
#Vb net textbox validating event errorprovider code#
true), then the whole conditional operator expression would be a constant expression and the code would compile. Incidentally, if the b = c part of your first example were changed to a constant expression (e.g. Basically what this boils down to is that the compiler can easily determine at compile time that these conversions are valid, so it allows them. As shown in this table, there is no implicit conversion from int to uint, so this is not allowed.īecause there is special treatment of numeric types when the value is a constant expression.įrom section 6.1.9 of the C# specification:Ī constant expression of type int can be converted to type sbyte, byte, short, ushort, uint, or ulong, provided the value of the constant-expression is within the range of the destination type.Ī constant expression of type long can be converted to type ulong, provided the value of the constant expression is not negative.Īs indicated in the first bullet a = 0 and a = 1 are both allowed because 0 and 1 are constant expressions and are valid uint values. The type of the expression b = c ? 0 : 1 is int. You are already halfway there if you are considering making a class to hold your validation logic this will get you the rest of the way in your new design. Later if a better idea of displaying warning vs errors comes along I can make the change in the Form itself rather mucking around with the View logic or the validate in Shape Program. The View doesn't care if the Form is displaying yellow for warning and red for error. How it actually is implemented is handled by the Form itself in it's implementation of the Interface. If the email address is not in the standard format (containing '' and '.'), the validation fails, an ErrorProvider icon is displayed, and the event is canceled. The following code example uses the derived class TextBox and validates an email address that the user enters. The View takes care of that instructing the Form what to do through the Interface. Public Custom Event Validating As CancelEventHandler Event Type CancelEventHandler Examples. Also different levels of severity is handled differently.
#Vb net textbox validating event errorprovider software#
Way back when I designed the software I decided how the UI going to work for textboxes, listboxes, combo boxes, etc. I don't have to go modify each control or even really worry about the different types of controls on the form. The advantage of this approach that validation is centralized in one location for a given Shape Program. Is OK to shift the focus to the next entry. ValidateTextBox(textbox) ' See if this is the first in the tab order so ' far. (You can set the error to the control by name, or generically by using the sender argument.In my own application I need to validate dimensions as they are typed in. Dim firsttextbox As TextBox Nothing Dim firsttabindex As Integer Integer.MaxValue For Each textbox As TextBox In mLikeInfo.Keys ' Validate the TextBox. If the input is not valid, we set the error shown by the ErrorProvider (the e.Message is generally the same as the Message parameter of any exception that has been thrown). We also clear any errors in the ErrorProvider (not sure of the best way to use this control, but this works).
In that event handler, we check if the input is valid (don't know what all that does, but it works - play with it) and, if so, cast the value to the correct data type in order to use for some purpose. The example shows us setting the type of data which should be entered into the text box and then subscribing to the corresponding event. It's really useful when combined with the above data validation method. Private Sub TextBox1Validating (ByVal Sender As Object, ByVal e As ) Handles TextBox1.Validating If Not IsNumeric (TextBox1.Text) Then ErrorProvider1.SetError (TextBox1, 'Not a numeric value.') Else Clear the error. The ErrorProvider is a WinForms control that allows you to show a red exclamation mark with an error message tooltip next to a control. The second argument is the error text to display. When the mask is blank, you can accept input just like you can with a TextBox.
What you should be aware of, though, is that the Mask is *not* required. If you want to read about the MaskedTextBox, it's all on MSDN. If you do this, as well as subscribe to the TypeValidationCompleted event, on the form Load event, you can handle user validation inside your TypeValidationCompleted event handler.
The trick is to set the ValidatingType of the MaskedTextBox control to the type of data you want to get from the user.
I just discovered that the MaskedTextBox control allows you to set the type of data which should be entered in the control and helps you do the validation of that data when necessary.