method not working on combox event selected index change

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C#

two method for two combobox binding on a form

private void cbBookBinding()
{
bHadithBook.DataSource = objSearch.SelectHadithBookName();
            cbHadithBook.DisplayMember = "Book_English_Name";
            cbHadithBook.ValueMember= "Book_Id";
           

            objSearch.HadithBookNo = Convert.ToInt32(cbHadithBook.SelectedValue);
}
 private void cbHadtihBaabBinding()
{

            cbBaab.DataSource = objSearch.SelectHadithBaabEnglish();
            cbBaab.DisplayMember = "[Baab_English_Name]";
            cbBaab.ValueMember = "[Baab_Id]";
           
            objSearch.HadithBookId = Convert.ToInt32(cbBaab.SelectedValue);



            dgvHadith.DataSource = objSearch.SelectHadithText();
}

i placed both method on event
1: combobox selected index change
and
2: For Load
this two method working find behind Form Load event
but on combobox selected index change this is not working. even i try to select another option from combbox but the one selected first remain selected in combobx. nothing change in combox and on gridview.