Populate a dropdown list from db

问题

I have an mvc 3 application with 2 tables in my entity framework.

PurchaseTable which was PurchaseID,PurchaseDate & ProductID I have another table called Product which contains ProductID and ProductName. creating a new view to insert a new purchase how do I change the textbox in the view for ProductID to be a dropdown bound by the ProductName in the Product table?

回答1:

Create a ViewModel:

public class CreatePurchaseViewModel
{
   public Purchase Purchase { get; set; }
   public IEnumerable<SelectListItem> Products { get; set; }
   public int SelectedProductId { get; set; }
}

Setup the View with the ViewModel:

[HttpGet]
public ActionResult CreateProduct()
{
   var model = new CreatePurchaseViewModel
   {
      Products = repository.FindAllProducts().Select(x =>
              new SelectListItem
              {
                  Text = x.ProductName,
                  Value = x.ProductId
              }
   };

   return View(model);
}

Then simply bind to the ViewModel and use the DropDownListFor HTML Helper:

<! -- other code to bind to Purchase, and then: -->

<%= Html.DropDownListFor(x => x.SelectedProductId, Model.Products) %>

Then when you submit the form, the SelectedProductId value in the model will be populated with the selected value from the dropdown list.

回答2:

The answer is easier than it looks. Simply create a list:

myDropDown = new SelectList(db.Products, "Product_ID", "ProductName", idSelected);

The first parameter is your table ("Products" from the Entity Model), the second is the "id" that will be returned when selecting from the list (i.e SelectedValue), the third is the "text" that will be displayed in the list and the last parameter is the currently selected item.

Assuming your model is called MyTablesDB, then:

MyTablesDB db = new MyTablesDB();

For example:

public SelectList GetPullDown(object idSelected) {
    myTablesDB myDB = new MyTablesDB();
    return new SelectList(myDB.Products, "Product_ID", "Product_Name", idSelected);
}

Cheers,

来源：https://stackoverflow.com/questions/4827243/populate-a-dropdown-list-from-db