Try this:
Dim fileReader As String
fileReader = FileSystem.ReadAllText("ResourceFile.txt")
FileReader.Text=fileReader
And by the way, it's very confusing and general bad practice to have a string named fileReader and a textbox named FileReader. You need to start using some kind of naming convention before you go crazy. Put some kind of code before your variable name to distinguish that it's a string or a textbox. For example, name your textbox txtFileReader and the string strFileReader.
Hope this helps.