Orzeh is right on this. Here is some sample code :

[System.ComponentModel.TypeConverter(typeof(DataSourceIDConverter))]
public String DataSourceID {
    get {
        String s = (String)ViewState["DataSourceID"];
        return (s == null) ? String.Empty : s;
    }
    set {
        ViewState["DataSourceID"] = value;
    }
}

protected Control DataSource {
    get {
        if (DataSourceID == String.Empty)
            return null;
        else
            return NamingContainer.FindControl(DataSourceID);
    }
}

With the right TypeConvertor you can show a dropdownlist with only the IDs of the type of controls you want to attach (in this case only DataSource controls).


Have fun.