Let’s assume when we click our save button that we wish to validate the controls and display an icon if there is a problem.
First, add the following code to the Form’s constructor after the Initialize Component method: This is a handy trick to prevent implicit validation of our controls when they lose focus.
Data input validation in Windows Forms is essential.
Built-in validation doesn't go much further than an enforcable maximum length for textboxes, but there are some nice methods you can use to make validation a breeze.
We will implement the business rule to allow test appointments to be setup on weekdays only using validation on the form.
Add controls as shown in the figure below and set the properties of the controls as indicated in the table. The control is added to the form and displayed in the control tray in the Windows form in Design view. Now we will add the validations for the Date Time Picker controls which collects the Test Date information.
You can also display errors that occur in Data Sets.
If the user enters invalid data they’ll see an icon shown in Figure 3.
After the validating event returns without being cancelled, meaning we have valid user input, then the validated event will be raised.
Let's say you have a form with textbox control, textbox1.
Place an errorprovider control on the form (it is not a visible control).