Data Annotation Attributes in ASP.NET MVC

Data Annotation Attributes in ASP.NET MVC

Here are the numerous types of Data Annotations with the syntax:

1) DataType

This attribute is used to specify the data type of the model.

Syntax

[DataType(DataType.Text)]

2) Required

This attribute defines the particular value as mandatory for a certain requirement 

Syntax

[Required(ErrorMessage="Please enter your name"),MaxLength(50)]

3) StringLength

Using this annotation attribute, we can set the maximum and minimum string range of the property.

Syntax

[StringLength(50,ErrorMessage="Please do not enter values over 50 characters")]

4) MaxLength

With this annotation attribute, we can set the maximum length of the property.

Syntax

[MaxLength(5)]

5) Range

We can apply the Range annotation attribute to define the range between two numbers.

Syntax

[Range(50,250,ErrorMessage="Please enter the correct value")]

6)Bind

This annotation attribute defines fields to enter or eliminate for model binding.

Syntax

[Bind(Exclude = "EmployeeID")]

7) DisplayFormat

This annotation attribute enables us to set the date format defined as per the attribute.

Syntax

[DisplayFormat(DataFormatString = "{0:MM.DD.YYYY}")]

8) DisplayName

With this annotation attribute we can set the property names that will  display at the view.

Syntax

[Display(Name="Employee Name")]

9) RegularExpression

Using this attribute, we can set a regex (regular expression) pattern for the property. For example, Email ID.

Syntax

[RegularExpression(@"^\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$", ErrorMessage = "Your Email is not valid.")]

10) ScaffoldColumn

Specifies whether scaffolding is used by a class or a data column.

Syntax

[System.AttributeUsage(System.AttributeTargets.Field |    System.AttributeTargets.Property, AllowMultiple=false)]

public class ScaffoldColumnAttribute : Attribute

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In Data Annotations, we have two types of namespaces that have their specific in-build types.

1. System.ComponentModel.DataAnnotations incorporate the subsequent attributes that affect and check the size or nullability of the column.

• MinLength
• MaxLength
• StringLength
• Key
• Timestamp
• ConcurrencyCheck
• Required

2. System.ComponentModel.DataAnnotations.Schema namespace comprises the subsequent attributes that reshape the schema of the database.

• Index
• ForeignKey
• NotMapped
• InverseProperty
• Table
• Column

Why Do We Need Data Annotation Attributes in ASP.NET MVC?

In ASP.NET MVC web applications, we have the three types of data validations:

Client-Side Validation: HTML/JavaScript validation

Server-side Validation:

•    ASP.NET MVC Model validation 
•    Database validation

Here we have ASP.NET MVC model validation that is a more secure validation whereas HTML/JavaScript validation is unsafe and can break after disabling the javascript while running the application.

ASP.NET MVC Framework implements a framework described as Data Annotation which is utilized for model validation. It is derived from System.ComponentModel.DataAnnotations assembly.

We can use Data Annotation to implement the model validation and can utilize it to model class properties.

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What Are the Validations?

Validation is the set of rules which we define on the input fields on the webform page. We have certain types of validations which we can use as per the user requirements:

1. Client-Side Validation
2. Server-side Validation

In ASP.NET MVC, we have a System.ComponentModel.DataAnnotations assembly which has several built-in validation types of attributes’ properties which we can implement as per the code logic.

• Required
• Data type
• RegularExpression
• Compare
• StringLength
• Range
• Credit Card number
• Currency
• Multi-line text
• Custom
• Date or DateTime
• Duration
• Email Address
• HTML
• Image URL
• Password
• Upload
• Phone number
• Postal Code

Built-in Validation Attributes

In ASP.NET MVC, we can consider Built-in validation attributes as custom validation. Below are a few examples:

• Compare: It validates and matches two fields' properties in a model.
• Range: It validates when a certain property value comes into a certain range.
• RegularExpression: It validates when a property value meets a certain regular expression.
• Remote: It works on a remote validation; we can call an action method function on the server and validate specific inputs on the client's side.
• DevExtremeRequired: It validates when the certain boolean property value is true or false.
• Custom : It allows you to define a custom validation attribute.

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Enabling Client-Side Validation in ASP.NET MVC Application

To enable the client-side validation, we can use JQuery and Javascript. Before using it, we should take the reference of the JavaScript files from the Scripts folder of your .net solution.

Example: jquery.validate.unobtrusive.js and query.validate.min.js 

Below is the layout example:

<!DOCTYPE html>

<html>

<head>

    <meta charset="utf-8" />

    <meta name="viewport" content="width=device-width, initial-scale=1.0">

    <title>@ViewBag.Title - Example Data annotation in MVC Application</title>

    @Styles.Render("~/Content/css") 

    @Scripts.Render("~/bundles/modernizr")

</head>

<body>

     @Html.Partial("_HeaderNavBar");   

    <div class="container body-content">

        @RenderBody()        

        <hr />

        <footer>

            <p>&copy; @DateTime.Now.Year - My ASP.NET Application</p>

        </footer>

    </div>

    @Scripts.Render("~/bundles/jquery")

    @Scripts.Render("~/Scripts/jquery.validate.min.js")

    @Scripts.Render("~/Scripts/jquery.validate.unobtrusive.min.js")

    @Scripts.Render("~/bundles/bootstrap")

    @RenderSection("scripts", required: false)

</body>

</html>

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Conclusion

We hope this article helped you understand Data Annotation in MVC using C#. In this article, we discussed the concept of data annotation and its various types, and validations with examples that will be helpful to professional developers from Java and .net backgrounds, application architectures, and other learners looking for information on JavaScript events.

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