Question

I have a drop down list that is bound to some items. i want to replace the selected item with a text box value and again want to bind the dropdownlist with new values.
For this i am currently storing the dropdown list items in a temporary List. How can I replace the current selected item with textbox value.

for (int i = 0; i < DropDownEmail.Items.Count; i++)
          {

                if (?)
                {
                    ObjRegistration = new ClassRegistration();
                    ObjRegistration.UserName = TextBoxEmail.Text;
                    tempEmailList.Add(ObjRegistration)
                }
                else{
                    ObjRegistration = new ClassRegistration();
                    ObjRegistration.UserName = DropDownEmail.Items[i].Text;
                    tempEmailList.Add(ObjRegistration);  
               }                     
          }

Answer 1

Your code doesn’t make much sense as it is written now, but in general, if you want to replace an item in a dropdown list you need to do something like this:

 var selectedItem = tempEmailList.SelectedItem; //returns a ListItem object
 selectedItem.Text=txtField.Text;
 dropDownList.DataBind();  //Rebind it so you see the change.

In your case, it seems that you are binding to a custom collection of ClassRegistration but since you are doing this on code-behind, once you bind the elements to the Dropdown list for the first time, you only have a reference to the Items collection in the dropdown which are all of type ListItem.

You can, alternatively, update your underlying custom collection and rebind that to the dropdown list:

var tempEmailList= ... //get it from DB or whatever

tempEmailList.Find(x => x.ID == int.Parse(ddl.SelectedItem.Value)).UserName = txtBox.Text;

ddl.DataSource = tempEmailList;//re-assing the datasource
ddl.DataBind();//rebind