ASP.NET is a widely regarded platform primarily because of its characteristics that enable developers to utilize it for creating compelling and dynamic web applications. Validating user data is the critical step for web application development securing the privacy of gathered data. ASP.NET provides a variety of validation controls that developers can use to confirm the achievements of user inputs (correctness, authentication, and security). In this post, we will look at different types of validation controls in ASP.NET and offer within this context detailed explanations accompanied by code samples.

Required Field Validator:

The RequiredFieldValidator is considered to be the most utilized member of the validation controls in ASP.NET, hence you can easily spend much time working with it. Validating an appropriate value for a specific field will give notice to the user whenever the user input is empty. It would display an error message when no data is supplied. Here lies the ultimate power of web forms that demand mandatory entries like "email addresses" and "passwords".

<asp:Label ID="lblName" runat="server" Text="Name"></asp:Label>

<asp:TextBox ID="txtName" runat="server"></asp:TextBox>

<asp:RequiredFieldValidator ID="rfvName" runat="server" ControlToValidate="txtName" ErrorMessage="Please enter a name"></asp:RequiredFieldValidator>

In this code snippet:

  • The `Label` control (`lblName`) ensures the text "Name" shows the user which field it is.
  • The `TextBox` control (txtName) displays the name that users enter.
  • `rfvName` will be an instance of `RequiredFieldValidator` control and it will be associated with `txtName`, which guarantees that users input something before proceeding.

Regular Expression Validator

The RegularExpressionValidator is responsible for controlling the rigidity of a field according to a predefined regular expression. This is the way it is to ensure that the data format is complex, for example, email addresses or phone numbers.

<asp:Label ID="lblEmail" runat="server" Text="Email"></asp:Label>

<asp:TextBox ID="txtEmail" runat="server"></asp:TextBox>

<asp:RegularExpressionValidator ID="revEmail" runat="server" 
ControlToValidate="txtEmail" ValidationExpression="\w ([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*" ErrorMessage="Please enter a valid email address!"></asp:RegularExpressionValidator>

In this code snippet:

  • The `Label` control (`lblEmail` )with Text ="Email" is used to `label` the field.
  • The control of `TextBox` (`txtEmail`) prompts for the user to input their email address.
  • `revEmail` is a `RegularExpressionValidator` control that assures the text entered in the `email` field matches the specified pattern.

Validator For Comparison

The CompareValidator controls the equality of two input field values thus improving the pair of fields till they meet the specified criteria. It is often served as verification of a password or comparing numbers, for example.

<asp:Label ID="lblPassword" runat="server" Text="Password"></asp:Label>

<asp:TextBox ID="txtPassword" runat="server" TextMode="Password"></asp:TextBox><br/>

<asp:Label ID="lblConfirmPassword" runat="server" Text="Confirm Password"></asp:Label>

<asp:TextBox ID="txtConfirmPassword" runat="server" TextMode="Password"></asp:TextBox>

<br />

<asp:CompareValidator ID="cvPassword" runat="server" 
ControlToValidate="txtConfirmPassword"ControlToCompare="txtPassword" 
Operator="Equal" Type="String" ErrorMessage="Passwords do not match">
</asp:CompareValidator>

In this code snippet:

  • Two `TextBox` controls (`txtPassword`, and `txtConfirmPassword`) are in place to accommodate users' passwords in different fields. The `TxtPassword` field is for entering a password while `TxtConfirmPassword` is where users confirm their passwords.
  • Another control that is embedded in the `CompareValidator` control (`cvPassword`) compares the entry of the second password with the initial password.

Range Validator

The RangeValidator is responsible for the values of any fields that must be within a given range. It is essential for checking the accuracy of numerical values like age or income, since some of them may be incorrect.

<asp:Label ID="lblAge" runat="server" Text="Age"></asp:Label>

<asp:TextBox ID="txtAge" runat="server"></asp:TextBox>

<asp:RangeValidator ID="rvAge" runat="server" ControlToValidate="txtAge" MinimumValue="18" MaximumValue="100" Type="Integer" ErrorMessage="Please enter an age from 18 to 100"></asp:RangeValidator>

In this code snippet:

  • `Label` control (`lblAge`) displays the words "Age" to indicate the field instead.
  • The `TextBox` control (`txtAge`) accepts users' inputs, which contain the text the user has entered their age.
  • The `RangeValidator` control (`rvAge`), only allows entering an age within the range.

Custom Validator

Through the CustomValidator attribute, developers are given the ability to create custom rules for validation. It is perfect for the job when strong validation logic is needed and cannot be implemented with the built-in validators.

protected void ValidateEmail(object sender, ServerValidateEventArgs e)
{
    string email = e.Value;
    if (email.Contains("@") && email.Contains("."))
    {
        e.IsValid = true;
    }
    else
    {
        e.IsValid = false;
    }
}

In this code snippet:

  • The `ValidateEmail` method is a server-side function that can be used with a `CustomValidator` control.
  • It runs the check through the given e-mail address to see if it has "@" and "." symbols in addition to other necessary elements for a valid e-mail address format.

Validation Summary

The ValidationSummary control is a mechanism for displaying all the validation errors on the web page. It is a handy addition for quick user reports of errors and their descriptions.

protected void btnRegister_Click(object sender, EventArgs e)
{
    if (Page.IsValid)
    {
        // Perform registration logic
    }
}

In this code snippet:

  • The event handler, `btnRegister_Click`, is the method that is a server-side function that gets triggered when the registration button is clicked.
  • It applies `Page.IsValid` to examine if all of the validation controls have satisfied validity.
  • Then if it's validation success, registration logic comes into effect.

We can execute our registration logic if all validation controls passed validation, and a summary of the validation errors that occurred on the web page will be shown by the Validation Summary control with ID “vsErrors” if any validation controls failed validation.

A precise, authentic, and secure user input must be given. Among the validation controls needed are Required Field Validator Control, Regular Expression Validator Control, Compare Validator Control, Range Validator Control CustomValidator Control, and ValidationSummary. By applying these validation controls, ASP.NET developers can enhance the quality of their web applications in terms of safety, precision, and ease of use as well as improve user experience.

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