autogenerate the value

hi i am a new user of Aso.Net. Please help me .. its urgent..
In my project i am having Dropdownlists and listboxes and also textboxes.
My question is when ever i click on the dropdownlist value corresponding value of that dropdownlist should be automatically generated.
For example if i select the value of Productname the ProductId should be automatically generated in the textbox.

Binding data to a textbox

You need to add code to the SelectedIndexChanged event of your drop down list that will assign the Text of textbox to a value based on the SelectedItem in the drop down list. You could use a switch statement to accomplish this.

swich(ddlProduct.SelectedIndex)
{
case 0:
textbox1.Text = "ProductId1";
break;
case 1:
textbox1.Text = "ProductId2";
break;
//and so on
default:
textbox1.Text = "Product Id not found";
break;
}

Nathan