I am looking for a solution where I will be able to add an image and text both in asp.net button.
By default, ASP .Net doesn't have a button which can render both image and text at the same time. However, you can achieve in two ways.
I prefer CSS because it is light weight, and you can style it whatever you want.
It works right out of the box. However, you cannot change their style easily.
Use third party control like Telerik RadButton.
Last but not least if you want, you can implement a custom server control by yourself.