Add an extension method to the DirectoryInfo class that searches the directory for files. This method should take an IEnumerable<string> parameter, listing patterns that the files should match (such as *.* or *.cs), optional target text that the files should contain, and a parameter indicating whether the search should include subdirectories.

Write a program to test your method. It should use a ComboBox control to allow the user to enter or select a sequence of file-matching patterns separated by semi-colons. Make the program allow the user to enter a multiline target string.