How to stop textchanged event from firing

I think you should query and check what values are stored in table.

Textchanged event cannot tamper values hence you are storing values incorrectly

I have checked it many times. It is getting saved as decimal. While fetching from table i use dataset ,i load data in the dataset and then assign it to textbox. The decimal value in the table i convert it to string and then assign to textbox

It is getting converted in dataset. Change the column type of dataset to decimal by default it is string

Sorry, i did not get what u r saying..This is the code

  txtqty.Text = DS.Tables[0].Rows[0]["Quantity"].ToString();

yes using Quick watch check the value of the following line

 DS.Tables[0].Rows[0]["Quantity"]