Examining the RequiredFieldValidator Validation Control
User input can be divided into two categories: required input and optional input. Required input is the set of inputs that the user must provide, whereas optional input is the set of inputs that the user may choose to provide or not to provide. In order to ensure that the user provides a response for a particular input, we can use a RequiredFieldValidator Web control.
To add a RequiredFieldValidator validation Web control to an ASP.NET Web page, all that we have to do is drag and drop the control from the Toolbox and onto the designer, just like we do with any other Web control. Go ahead and drag the RequiredFieldValidator Web control from the Toolbox onto the designer; place the Web control ...
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