una gamit ka ng class.mas madali coding dun isang connect lang then ttawagin mo kada form .if sa search lagay ka txtbox name if (txtSearch) then lagay kana din ng combobox for choosing the category para dyan muna din llagay yung validation mo .
code
string search="";
switch(combobox.SelectedIndex){
case 0:
sql = "SELECT * FROM students WHERE SNo LIKE '%" + txtSearch.Text + "%'";
break;
}
crudtools.Filldatagrid("select * from tbletc",ref dataGridView);