C# windows form validation controls

If you want to change icon errorprovider c , you can add an imagelist control to your winform, then set icon to the error provider control as the following c code. You can also change the blink style to NeverBlink if you don't want to scare the user. This post shows you How to use Error Provider in C. Error Provider control that helps you validation data in c winform. Show txtUsername. Text, "Message", MessageBoxButtons. OK, MessageBoxIcon.

If the postal code must belong to a specific group of zip codes, you can do a string comparison on the input to validate the data entered by the user. If the postal code must be in a specific form, you can use regular expressions to validate the data entered by the user. For more information about regular expressions, see. If the postal code must be a valid United States Zip code, you could call a Zip code Web service to validate the data entered by the user.

The Validating event is supplied an object of type CancelEventArgs. If you determine that the control's data isn't valid, cancel the Validating event by setting this object's Cancel property to true. If you don't set the Cancel property, Windows Forms will assume that validation succeeded for that control and raise the Validated event. For a code example that validates an email address in a TextBox , see the Validating event reference.

Validation is useful when you have bound your controls to a data source, such as a database table. By using validation, you can make sure that your control's data satisfies the format required by the data source, and that it doesn't contain any special characters such as quotation marks and back slashes that might be unsafe. When you use data binding, the data in your control is synchronized with the data source during execution of the Validating event.

If you cancel the Validating event, the data won't be synchronized with the data source. If you have custom validation that takes place after the Validating event, it won't affect the data binding. For example, if you have code in a Validated event that attempts to cancel the data binding, the data binding will still occur.

In this case, to perform validation in the Validated event, change the control's Binding. Never , and add your-control. WriteValue to your validation code.

So when does a control's data get validated? This is up to you, the developer. You can use either implicit or explicit validation, depending on the needs of your application. The implicit validation approach validates data as the user enters it. Validate the data by reading the keys as they're pressed, or more commonly whenever the user takes the input focus away from the control.

This approach is useful when you want to give the user immediate feedback about the data as they're working. If you cancel the Validating event, the behavior of the control will be determined by what value you assigned to AutoValidate. If you assigned EnablePreventFocusChange , canceling the event will cause the Validated event not to occur.

Input focus will remain on the current control until the user changes the data to a valid format. This browser is no longer supported. Download Microsoft Edge More info.

Contents Exit focus mode. Validated Event Reference Is this page helpful? Please rate your experience Yes No. Any additional feedback? Namespace: System. Forms Assembly: System.