how to different error message based on search textbox

Question

I need to display error message when search textbox empty and user click search button not similar to error message when user input something not found 

 

for empty I know it is by check the textxbox

if (textbox1.text == " "){

label1.text= " type something or any message ";

}

 

 but for searching    the typing matches or not that what I do need

please help