I made this line of code
mystring= Regex.Replace(mystring, @"\d+IEME", "E"); 
But got a problem because I want to keep the number. Like 7IEME replace to 7E
I made this line of code
mystring= Regex.Replace(mystring, @"\d+IEME", "E"); 
But got a problem because I want to keep the number. Like 7IEME replace to 7E
 
    
     
    
    Capture \d+ with a group and then for replacing, use $1 which means "Group 1" followed by E.
mystring= Regex.Replace(mystring, @"(\d+)IEME", "$1E"); 
 
    
    You should be using groups:
string mystring = "7IEME";
mystring= Regex.Replace(mystring, @"(\d+)IEME", "$1E"); 
