Error with trying to set a Command Argument for my Gridview C#

What am I missing? I am trying to set the command argument to the EventId from my DTO object in C#. I am getting an error: server tag is not well formed:

asp:Button ID="btnEditDelete" runat="server" Text="Edit/Delete" CssClass="btnStyle" Line 44: CommandName="BtnEditDelete" CommandArgument="<%# DataBinder.Eval(Container.DataItem, "EventId", "{0}") %>"/> ...