Formatting data

Using DataType Attributes

Open the Movie.cs file and examine the Movie class. The System.ComponentModel.DataAnnotations namespace provides formatting attributes in addition to the built-in set of validation attributes. We've already applied a DataType enumeration value to the release date and to the price fields. The following code shows the ReleaseDate and Price properties with the appropriate DataType attribute.

[Display(Name = "Release Date")]
[DataType(DataType.Date)]
public DateTime ReleaseDate { get; set; }

[Range(1, 100)]
[DataType(DataType.Currency)]
[Column(TypeName = "decimal(18, 2)")]
public decimal Price { get; set; }    

• The DataType attributes only provide hints for the view engine to format the data and supplies elements/attributes such as <a> for URL's and <a href="mailto:EmailAddress.com"> for email.

• You can use the RegularExpression attribute to validate the format of the data.

• The DataType attribute is used to specify a data type that's more specific than the database intrinsic type, they're not validation attributes.

• In this case we only want to keep track of the date, not the time. The DataType Enumeration provides for many data types, such as Date, Time, PhoneNumber, Currency, EmailAddress and more.

• The DataType attribute can also enable the application to automatically provide type-specific features.

  • For example, a mailto: link can be created for DataType.EmailAddress, and a date selector can be provided for DataType.Date in browsers that support HTML5.

• The DataType attributes emit HTML 5 data- (pronounced data dash) attributes that HTML 5 browsers can understand.

  • DataType.Date doesn't specify the format of the date that's displayed.

  • By default, the data field is displayed according to the default formats based on the server's CultureInfo.

DisplayFormat attribute

The DisplayFormat attribute is used to explicitly specify the date format:

[DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
public DateTime ReleaseDate { get; set; }

The DataType Enumeration provides for many data types, such as Date, Time, PhoneNumber, Currency, EmailAddress and more.

The ApplyFormatInEditMode setting specifies that the formatting should also be applied when the value is displayed in a text box for editing. (You might not want that for some fields — for example, for currency values, you probably don't want the currency symbol in the text box for editing.) You can use the DisplayFormat attribute by itself, but it's generally a good idea to use the DataType attribute.

The DataType attribute conveys the semantics of the data as opposed to how to render it on a screen, and provides the following benefits that you don't get with DisplayFormat:

• The browser can enable HTML5 features (for example to show a calendar control, the locale-appropriate currency symbol, email links, etc.)

• By default, the browser will render data using the correct format based on your locale.

• The DataType attribute can enable MVC to choose the right field template to render the data (the DisplayFormat if used by itself uses the string template).

You can use the DisplayFormat attribute by itself, but it's generally a good idea to use the DataType attribute. The DataType attribute conveys the semantics of the data as opposed to how to render it on a screen!