Question

I had datalist and I had ddl on it and user can select value from ddl to bind datalist. When I tried to find ddl in datalist when user select value, this error apeared

Index was out of range. Must be
non-negative and less than the size of
the collection. Parameter name: index

here

DDLProduct2 = (DropDownList)DLProduct.Items[DLProduct.EditItemIndex].FindControl("DDlProduct");

so please any one help me.

private DropDownList DDLProduct2;

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            ProductByProductID();
            CategoryParentZero();


        }
    }
 protected void DDlProduct_SelectedIndexChanged(object sender, EventArgs e)
    {
        DDLProduct2 = (DropDownList)DLProduct.Items[DLProduct.EditItemIndex].FindControl("DDlProduct");
        if (DDLProduct2 != null)
        {
            if (DDLProduct2.SelectedIndex > 0)
            {
                using
                (SqlConnection conn = Connection.GetConnection())
                {
                    SqlCommand cmd = new SqlCommand();
                    cmd.Connection = conn;
                    cmd.CommandType = CommandType.StoredProcedure;
                    cmd.CommandText = "SP_GetProductsByProductID";
                    SqlParameter ParentID_Param = cmd.Parameters.Add("@ProductID", SqlDbType.Int);
                    ParentID_Param.Value = DDLProduct2.SelectedValue;
                    ;
                    DataTable dt = new DataTable();
                    SqlDataAdapter da = new SqlDataAdapter();
                    da.SelectCommand = cmd;
                    da.Fill(dt);
                    DLProduct.DataSource = dt;
                    DLProduct.DataBind();

                }
            }
        }

    } 

Answer 1

DLProduct.EditItemIndex should be equal to -1 because the is nothing edited

just add an if DLProduct.EditItemIndex >= 0 before the line throwing the error