change selecteditem of dropdownlist after binding

Question

i have a droplist in page that i bind this with code

 Category catObj = new Category();
    dropCat.DataSource = catObj.GetAllCategory();
    dropCat.DataTextField = "Title";
    dropCat.DataValueField = "CategoryID";
    dropCat.DataBind();

i want change selected item of droplist with ths code

dropCat.SelectedIndex = Convert.ToInt32(catObj.ParentId);

but this code cant change the selected item please help me thank you all

Answer 1

I'll assume that you're trying to select by value and not by index since catObj.ParentId is likely to contain a CategoryId. In case my assuption is correct, you'll need to do this

dropCat.SelectedValue = catObj.ParentId.ToString();

DropDownList.SelectedIndex property refers to a position inside Items collection and not about the value of the item.