Regex to find some text in a string c#

Its like a filtering, i have a list of string and a text box. Text that is entered in the textbox, should be filtered. Am planning to use Regex for this.

so am looping the strings and it should be check the textbox text is contains in this strings are not.

Please suggest the regex format to achieve this.

Please don't suggest a better way, since i need to be strict with this flow.

Update: What exactly am looking for is, "%"+searchTextBox.Text+"%" Regex for this statement