Parameter query problem

[naanaa]

Hello
Anybody knows how parameter can be passed in correctly:
There are 2 table, "sp" is one of the table that will be used depending on a session. I need to pass a dropdownlist value into the query like:

table123.ID = ddlItem.Selecte dValue;
GetLists(table1 23);

public DataSet GetLists(table123 pref)
{
new SqlCommand("select b.ID2 from " + sp + " a, tb2 b where a.ID=b.ID and d.ID=@id", cn);

cm.Connection = cn;

cm.Parameters.Add(p1);

cm.Parameters[@id].Value = pref;

ds = new DataSet();

da = new SqlDataAdapter(cm);

da.Fill(ds, "GetLists"); 

return ds;

}

[OuTCasT]

Dim ex as string
ex = ddlItem.Selecte dValue

then pass ex to the query string.