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.SelectedValue;
GetLists(table123);

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.SelectedValue

then pass ex to the query string.