Validating user input in windows forms
You can use either implicit or explicit validation, depending upon the needs of your application. You click the "Submit" button, it will not close the window while there are still errors. Important If you have custom validation that takes place after the Validating event, it will not affect the data binding. For more information about regular expressions, see. Below is a table of the most common controls and their defaults. If you assigned EnableAllowFocusChange , the Validated event will not occur when you cancel the event, but focus will still change to the new control. Call ValidateChildren to validate all child controls in a form or container control.
Besides, when you drop a ErrorProvider to a Form, it will automatically generate a line like: To validate your controls, you will have to use explicit validation. How do Color and Lines properties do this? You can use either implicit or explicit validation, depending on the needs of your application. This is up to you, the developer. The control displays a set of prompts to the user. Those properties will always be edited by the specified editor in the property window. You may require that certain text fields not be zero-length, that a field be formatted as a phone number or other type of well-formed data, or that a string not contain any unsafe characters that could be used to compromise the security of a database. Event-Driven Validation If you want full programmatic control over validation, or need to perform complex validation checks, you should use the validation events built into most Windows Forms controls. Call Validate to validate the last control to have lost focus. Points of Interest In this section, I want to say more about advanced components programming. The masking language that is used by MaskedTextBox is very flexible. If you assigned EnablePreventFocusChange , canceling the event will cause the Validated event not to occur. For a full demo, I have got a "register" example for you, please analyse it yourself. Below is a table of the most common controls and their defaults. Component Designer Have you noticed that, if you set the focus on a ListView control at design time, there appears a triangle button on it. You may require that certain text fields not be zero-length, that a field be formatted as a telephone number or other type of well-formed data, or that a string not contain any unsafe characters that could be used to compromise the security of a database. The component must implement the IExtenderProvider interface. When you use data binding, the data in your control is synchronized with the data source during execution of the Validating event. Assigning Disable to the AutoValidate property prevents implicit validation altogether. Bo Shen, who checks my article and corrects my English. WriteValue to your validation code. Here, I will assume you that have basic components programming skills, like creating a component class, applying DefaultValue, DefaultEvent, and Browsable attributes, and so on. Input focus will remain on the current control until the user changes the data to an appropriate format. This can be useful when you want to validate controls based on some user event, such as a button click, or when you want to validate an entire form at once instead of on a control-by-control basis.
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