Use of RegisterClientScriptBlock/RegisterStartupScript in asp.net 3.5

RegisterStartupScript is used to register and execute javascript functions once the page finished loading, this javascript code executes before the onLoad event of page is raised. You can use it for multiple reasons, for example, you want to execute any particular javascript function depending on some variable value in your code behind.

On the other hand, RegisterClientScriptBlock is used to add a script block on the top of your page, similarly it provides you a way to work with both client side code and server code in your code behind.