If your really good at this, you use JQuery client side programming, and either bind a blur event to the textbox, or create a textbox with a blur event that links to a JQuery Function. Then write a JQuery Ajax request to a web service, in which the web service returns the data you need, and do something with the result. In the web service, you perform all your server side programming, but it happens in the background without a postback to the server, keeping the web app smooth in motion and fast in speed. Introduction to using jQuery with Web Services[^] Other wise, you have to postback the textbox data to the server, and fetch new stuff and repopulate the HTML or form (Gridview) When developing on a local machine, folks forget about speed, and long it takes. So consider form design for this, Is this an optimum time to check the data entered, and force the user to wait 10 seconds or so?