How to set a value dynamically for dropdownlist in code behind C#

I need to set va开发者_如何学JAVAlue "Y" to dropdownlist control dynamically.When i tried by selectedValue it gave error like object reference is null .plz help

First make sure that Y is there inside your asp:DropDownList. Then do this

if (DropDownList1.Items.FindByValue("Y") != null)
{
     DropDownList1.Items.FindByValue("Y").Selected = true;
}

Assuming that "Y" is in your dropdownlist:

DropDownList1.SelectedValue=DropDownList1.Items.FindByValue("Y").Tostring();

It works.

SelectedValue will only work when using data binding. If you filled out the list manually via the Windows Forms Designer in Visual Studio or by manipulating the DropDownList.Items collection, you need to use SelectedItem as below:

DropDownList1.SelectedItem = "Y";