Insufficient stack to continue executing the program safely...... because an "if (IsPostback) " infinite loop

Im new to .Net and trying to build an project that involves 6 tables and now i was trying to take an Id from a table and bind it to a drop down list in the form that inserts data to another table (trying to get the Id_copil from copii table while the form is inserting data to Voluntari table)

Ive been looking up answers and seems that the problem is in this code :

if (!IsPostBack)
    {
        drpIngrijire.DataBind();
        drpResponsabil.DataBind();

    }

Now, im using our teachers handouts but i don't know how to solve this . can anyone help me here ?

Thanks in advance :)