Web Forms :: How To Reference A HTML Element By ID

my .aspx page a have this HTML element:

<table id="table7" runat="server"></table>

I want to use C# to put some rows inside ...

Of course, I chould do this:

table7.Rows.Add( ... );

But the problem is, I create the ID dynamically and I have multiple tables with IDs like "table1","table2", and so on....

string idFromDB = ... // retrieve the number from the database
string fullId = "table" + idFromDB;
HtmlTable tbl = .... get the element based on fullId .... ??????
tbl.Rows.Add( ... );

How do I reference the table element by the ID?