hi,
You can check using Lambda expression as below.
if(objdt.AsEnumerable().Where(c => c.Field<string>("Col1") == txtbox1.Text.Trim()).Count() > 0)
{
}
else
{
}
this will check the existence of the textbox value in datatable, if count > 0 , then that value exists in table else not.
More on lambda expression[
^]
hope it helps.