A String can be added to an Integer, if the string's value is an integer represented in the form of string. For e.g. strings like "300", "57" can be added to any Integer. But not strings like "Area51". Hope that makes sense.
If you just want to display use the ToString() method on the integer and do a concatenation, or simply use String.Format.
string displayText = string.Format("string - {0}, int - {1}", stringvariable, intvariable);
Hope this helps.