How do I use data annotations in ASP.NET MVC?

How do I use data annotations in ASP.NET MVC?

Data annotations in ASP.NET MVC are attributes you can apply to model properties to enforce validation rules. For example, you can use the [Required] attribute to make a field mandatory.

Can you give me an example of how to implement the [StringLength] attribute?

Sure! You can use the [StringLength] attribute like this:

public class UserModel
{
    [StringLength(100, ErrorMessage = "Name cannot be longer than 100 characters.")]
    public string Name { get; set; }
}

This ensures that the Name property cannot exceed 100 characters.

What other data annotations are commonly used?

Some commonly used data annotations include [Range], [EmailAddress], [RegularExpression], and [Compare]. Each serves a specific validation purpose.

How do I display validation messages in the view?

You can display validation messages in your view using the Html.ValidationMessageFor helper method. For example:

@Html.ValidationMessageFor(model => model.Name)

This will show the validation error message for the Name property.