Part 41 - Using datatype and displaycolumn attributes in asp.net mvc application

we will discuss using datatype and displaycolumn attributes.

To understand DataType attribute, we will be using the same example, we used in Part 40. Copy and paste the following code in "Employee" class, and navigate to localhost/MVCDemo/Home/Details/1.
[MetadataType(typeof(EmployeeMetaData))]
public partial class Employee
{
}

public class EmployeeMetaData
{
    // Display mailto hyperlink
    [DataType(DataType.EmailAddress)]
    public string EmailAddress { get; set; }

    // Display currency symbol. For country specific currency, set 
    // culture using globalization element in web.config. 
    // For Great Britain Pound symbol
    // <globalization culture="en-gb"/>
    [DataType(DataType.Currency)]
    public int? Salary { get; set; }

    // Generate a hyperlink
    [DataType(DataType.Url)]
    public string PersonalWebSite { get; set; }

    // Display only Time Part
    // [DataType(DataType.Time)]
    // Display only Date Part
    [DataType(DataType.Date)]
    public DateTime? HireDate { get; set; }
}



DisplayColumn attribute is useful, when a class has a property of complex type, and you want to pick one property of this complex object for display purpose. Let's understand this with an example.

Right click on the "Models" folder and add Company.cs class file. Copy and paste the following code. 
public class Company
{
    public Employee CompanyDirector
    {
        get
        {
            SampleDBContext db = new SampleDBContext();
            return db.Employees.Single(x => x.Id == 1);
        }
    }
}

Notice that, this class has CompanyDirector property which returns an Employee object. Employee is a complex type. Employee object has got several properties. If you want FullName to be used for display purpose, then make the following changes.

Decorate "Employee" partial class in "Models" folder, with DisplayColumn attribute.
[MetadataType(typeof(EmployeeMetaData))]
[DisplayColumn("FullName")]
public partial class Employee
{
}

Change "Details" action method in "Home" controller as shown below.
public ActionResult Details(int id)
{
    Company company = new Company();
    return View(company);
}

Copy and paste the following code in Details.cshtml view
@model MVCDemo.Models.Company

@{
    ViewBag.Title = "Details";
}

@Html.DisplayTextFor(x => x.CompanyDirector)

Navigate to localhost/MVCDemo/Home/Details/1 and you should see the FullName of the employee.