Your question is pretty brief, but if if i think i understand what you want to do, you could try this in the codebehind:
List<string> ThisIsYourList = new List<string>();
Gridview1.DataSource = ThisIsYourList;
Gridview1.DataBind();
f you want to add a dropdownlist to every row, you need to add an itemtemplate to your gridview like this:
<asp:TemplateField>
<ItemTemplate>
<asp:DropDownList ID="DropDownList1" runat="server"/>
</ItemTemplate>
</asp:TemplateField>
You add this itemtemplate anywhere between the tags of your gridview.