how to retrieve the data of a perticular item from dropdown

I am new to work with MVC and I have confusion that how to retrieve the data of an item selected from the drop down list to the textbox. There are six items in the list and for each item there has different descriptions. This is my model class

public partial class Service { public int Id { get; set; } public string ItemName { get; set; } public string Description { get; set; } }

In this ItemName are the items in the dropdown list, and description is the data for each items in the dropdown, these values are stored in the table.

controller page

public async Task Edit(int? id){

if (id == null)

{return new HttpStatusCodeResult(HttpStatusCode.BadRequest);

}

Service service = await db.Services.FindAsync(id);

if (service == null)

{return HttpNotFound();

}

return View(service);

}// POST: Services/Edit/5

// To protect from overposting attacks, please enable the specific properties you want to bind to, for

// more details see http://go.microsoft.com/fwlink/?LinkId=317598.[HttpPost]

[ValidateAntiForgeryToken]

public async Task Edit([Bind(Include ="Id,ItemName,Description")] Service service)

{if (ModelState.IsValid){db.Entry(service).State = EntityState.Modified;await db.SaveChangesAsync();return RedirectToAction("Index");

}

return View(service);

}

Here how can I bind the id of the drop down items in the table to the edit action method??

view page